Moving Charges And Magnetism Questions

We provide moving charges and magnetism practice exercises, instructions, and a learning material that allows learners to study outside of the classroom. We focus on moving charges and magnetism skills mastery so, below you will get all questions that are also asking in the competition exam beside that classroom.

List of moving charges and magnetism Questions

Question No Questions Class
1 In figure,the cube is ( 40.0 mathrm{cm} ) on each
edge.Four straight segments of wire ( a b, b c, c d ) and ( d a ) form a closed loop that
carries a current ( mathrm{I}=5.00 mathrm{A}, ) in the
direction shown.A uniform magnetic
field of magnitude ( B=0.020 mathrm{T} ) is in the
positive y-direction.Determine the magnitude and direction of the
magnetic force on each segment
12
2 Only the current inside the Amperian loop contributes in
A. finding magnetic field at any point on the Ampere’s loop
B. line integral of magnetic field
( c . ) in both of the above
D. in neither of them
12
3 Magnetic field at a point on the line of current carrying conductor is
A. maximum
B. infinity
c. zero
D. finite value
12
4 A wire is bent in the form of a semicircle
of radius ( r ) and carries a current of ( i )
The magnetic induction at the centre of the semicircle is
A ( cdot frac{mu_{o} i}{2 r} )
в. ( frac{mu_{o} i}{8 r} )
c. ( frac{mu_{o} i}{4 r} )
D. ( frac{mu_{o} i}{r} )
12
5 A tiny bar magnet is kept close to a long current carrying straight wire placed along the z axis. When the center of the magnet is at ( (a, 0.0) ) and it is oriented along the z axis, it experiences
A. no net force but a net torque.
B. neither net force nor net torque
c. both a net force and a net torque.
D. a net force but no net torque
12
6 An electron beam passes through a
magnetic field of ( 2 times 10^{-3} W b / m^{2} ) and
an electric field of ( 1.0 times 10^{4} V / m ) both
acting simultaneously. The path of electron remains undeviating. The speed of electron if the electric field is removed, and the radius of electron path will be respectively.
A ( cdot 10 times 10^{6} m / s, 2.43 )
В. ( 2.5 times 10^{6} mathrm{m} / mathrm{s}, 0.43 )
c. ( 5 times 10^{6} mathrm{m} / mathrm{s}, 1.43 )
D. None of these
12
7 A rectangular coil ( 3 times 3 mathrm{cm} ) consisting of
100 turns caries 0.1 A. If it produces a
deflection ( 10^{0}, ) in a field of induction
( 0.1 T, ) the couple per unit twist is
A ( cdot 9 times 10^{-2} mathrm{Nm} / ) Degree
B. ( 9 times 10^{-5} mathrm{Nm} / ) Degree
C. ( 9 times 10^{-2} mathrm{Nm} / mathrm{rad} )
D. ( 0.9 mathrm{Nm} / ) Degree
12
8 An electron having a charge e moves with a velocity v in X-direction. A magnetic field acts on it in Y-direction. The force on the electron acts in
A. positive direction of Y-axis
B. negative direction of Y-axis
c. positive direction of Z-axis
D. negative direction of Z-axis
12
9 An electron of charge ( e ) and mass ( m ) is
moving in a circular loop of radius ( boldsymbol{r} )
with a uniform angular speed ( omega . ) Then
which of the following statements are
correct?
This question has multiple correct options
A. The equivalent current flowing in the circular path is proportional to ( r^{2} )
B. The magnetic moment due to circular current loop is independent of ( m )
C. The magnetic moment due to circular loop is equal to ( 2 e / m ) times the angular momentum of the electron
D. The angular momentum of the particle is proportional to the areal velocity of electron
12
10 Assertion
A beam of protons is moving towards east in vertically upward magnetic field.Then,this beam will deflect
towards south.
Reason
A constant magnetic force will act on the proton beam.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
11 7. A moving coil galvanometer has 150 equal divisions. Its
current sensitivity is 10 divisions per milliampere and
voltage sensitivity is 2 divisions per millivolt. In order
that each division reads 1 V, the resistance (in 2) needed
to be connected in series with the coil will be
(a) 9995
(b) 99995
(c) 100
(d) 103
(AIEEE 2005)
12
12 A conducting loop carrying a current
is placed in a uniform magnetic field
acting perpendicular to the plane of the coil shown in figure. the loop will have a tendency to
A. contract
B. expand
c. move towards positive X-axis
D. move towards positive Y-axis
12
13 The most suitable material to be used
as the core of an electromagnet is (soft, hard) iron.
12
14 The magnetic force between the infinite
wire and the square loop is
A ( frac{mu_{0} i^{2}}{4 pi}, ) repulsiv
B. ( frac{mu_{0} i^{2}}{2 pi}, ) repulsive
C ( frac{mu_{0} i^{2}}{4 pi}, ) attractive
D. ( frac{mu_{0} i^{2}}{2 pi}, ) attractive
12
15 A rectangular coil of wire of 500 turns of
area ( 10 times 5 c m^{2} ) carries a current of ( 2 A )
in a magnetic field of induction ( 2 times )
( 10^{-3} T . ) If the plane of the coil is parallel
to the field. The torque on the coil is (in
( N m) )
A . 0.1
B. 0.01
c. 0.001
D.
12
16 Find the distance ( x_{0} ) to the point on the
axis at which the value of ( B ) differs by
( eta=1 % ) from that in the middle section
of the solenoid.
A ( . x_{0} approx R )
в. ( x_{0} approx 7 R )
( mathbf{c} cdot x_{0} approx 5 R )
D. ( x_{0} approx 3 R )
12
17 A conducting bar with mass ( mathrm{m} ) and
length L slides over horizontal rails that
are connected to a voltage source. The
voltage source maintains a constant
current I in the rails and bar, and a
constant, uniform, vertical magnetic field ( vec{B} ) fills the region between the rails (as shown in fig). Find the magnitude and direction of the net force on the
conducting bar. Ignore friction, air resistance and electrical resistance :
A. ILB, to the right
B. ILB, to the left
c. ( 21 L ) B, to the right
D. 2ILB, to the left
12
18 You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper
wire and a switch. Label the poles of the electromagnet.
12
19 What is a toroid? Mention an expression
for magnetic field at a point inside a toroid?
12
20 The distance between the wires of
electric mains is ( 12 mathrm{cm} . ) These wires
exprience 4 mgwt per unit length. The value of current flowing in each wire will be if they carry current in same direction
A . ( 4.85 mathrm{A} )
B. zero
( mathbf{c} cdot 4.85 times 10^{-2} A )
D. ( 85 times 10^{-4} A )
12
21 The value of ( mu ) is ( 4 pi times 10^{-7} H m^{-1} )
A. True
B. False
12
22 The magnetic filed (dB) due to smaller element (dl) at a distance ( (vec{r}) ) from element carrying current i, is
( ^{mathbf{A}} cdot d B=frac{mu_{0} i}{4 pi}left(frac{vec{d} l times vec{r}}{r}right) )
B. ( d B=frac{mu_{0} i}{4 pi} i^{2}left(frac{vec{d} l times vec{r}}{r^{2}}right) )
( ^{mathbf{c}} d B=frac{mu_{0} i^{3}}{4 pi} ileft(frac{vec{d} l times vec{r}}{2 r^{2}}right) )
( ^{mathrm{D}} d B=frac{mu_{0}}{4 pi} ileft(frac{vec{d} l times vec{r}}{r^{3}}right) )
12
23 ( x )
( x )
0
( w )
12
24 Which of the following statement is not
correct about two parallel conductors
carrying equal currents in the same
direction?
A. each of the conductors will experience a force
B. the two conductors will repel each other
C. there are concentric lines of force around each
conductor
D. each of the conductors will move if not prevented from doing so
12
25 A solenoid of length ( 0.4 m ) and diameter
( 0.6 m ) consists of a single layer of 1000
turns of fine wire carrying a current of
( mathbf{5} times mathbf{1 0}^{-mathbf{3}} ) A. Calculate the magnetic
field on the axis at the middle and at
the end of the solenoid:
A ( cdot 8.7 times 10^{-6} T, 6.28 times 10^{-6} T )
B . ( 6.28 times 10^{-6} T, 8.7 times 10^{-6} T )
D. ( 8.7 times 10^{-6} T, 8.28 times 10^{-6} T )
12
26 A solenoid of length ( 0.4 m ) and having
500 turns of wire carries a current of
3 amp. Calculate the torque required to hold a coil (having radius ( 0.02 mathrm{cm} )
current ( 2 A ) and turns 50 ) in the middle
of the solenoid with its axis
perpendicular to the axis of the
solenoid. ( left(pi^{2}=10right) )
12
27 A proton is moving with velocity ( 10^{4} m / s ) parallel to the magentic field of
intensity 5 tesla.The force on the proton
is
A. ( 8 times 10^{-15} N )
B . ( 10^{4} N )
c. ( 1.6 times 10^{-19} N )
D. zero
12
28 Protons and ( alpha ) -particles of equal
momenta enter a uniform magnetic field normally. The radii of their orbits will have the ratio
( A )
B. 2
c. 0.5
( D )
12
29 The direction of the force on a current-
carrying wire placed in a magnetic field depends on
A. the direction of the current
B. the direction of the field
c. the direction of the current as well as field
D. neither the direction of current nor the direction of field
12
30 A solenoid of inductance ( 2 mathrm{H} ) carries a
current of ( 1 A . ) What is the magnetic
energy stored in a solenoid?
A . 2
B . 1 J
c. 4 J
D. 5 J
12
31 A solenoid of length ( 1.5 mathrm{m} ) and ( 4 mathrm{cm} )
diameter possesses 10 turns per ( mathrm{cm} . ) A current of ( 5 mathrm{A} ) is flowing through it, the magnetic induction at axis inside the
solenoid is ( left(mu_{0}=4 pi timesright. )
( left.10^{-7} w e b e r a m p^{-1} m^{-1}right) )
A ( cdot 4 pi times 10^{-5} ) gauss
В . ( 2 pi times 10^{-5} ) gauss
c. ( 4 pi times 10^{-5} ) tesla
D. ( 2 pi times 10^{-5} ) tesla
12
32 Draw the magnetic field lines for a
current carrying solenoid when a rod made of
(i) copper, (ii) aluminium and
(iii) iron are inserted within the
solenoid as shown.
12
33 Toroid is
A. ring shaped closed solenopid
B. rectangular shaped solenoid
C. ring shaped open solenoid
D. square shaped solenoid
12
34 A cyclotron is used to accelerate
A. Neutron
B. Only positively charged particles
C . Only negatively charged particles
D. Both positively and negatively charged particles
12
35 Find out the arrow or arrows which give
the direction of a force vector.
A. Arrow A only
B. Arrow B only
c. Arrow c only
D. Arrows A and D
E. Arrows B and E
12
36 If a charged particle goes unaccelerated in a region containing electric and magnetic fields This question has multiple correct options
A. ( vec{E} ) must be perpendicular to ( vec{B} )
B . ( vec{v} ) must be perpendicular to ( vec{E} )
c. ( vec{v} ) must be perpendicular to ( vec{B} )
D. ( E ) must be equal to ( v B )
12
37 (a) State Ampere’s circuital law. Use this law to obtain the expression for the magnetic field inside an air cored toroid of average radius r having ‘n’ turns per unit length and carrying a steady current I
(b) An observer to the left of a solenoid of N terms each of cross section area ( A )
observes that a steady current lin it flows in the clockwise direction. Depict the magnetic field lines due to the solenoid specifying its polarity and show that it acts as a bar magnet of
magnetic momentum ( boldsymbol{m}=boldsymbol{N} boldsymbol{I} boldsymbol{A} )
12
38 A closely wound solenoid ( 80 mathrm{cm} ) long
has 5 layers of winding of 400 turns each. The diameter of the solenoid is
1.8 ( c m . ) If the current ( 8.0 A ) flows in it
the magnitude of magnetic field inside the solenoid near its centre will be
( mathbf{A} cdot 8 pi times 10^{-3} T )
В . ( 6 pi times 10^{-3} T )
c. ( 4 pi times 10^{-3} T )
D. ( 3 pi times 10^{-3} T )
12
39 The deflection in a moving coil galvanometer falls from 50 divisions to
10 divisions when a shunt of ( 20 Omega ) is
connected with it. The resistance of
galvanometer coil is?
A . ( 48 Omega )
B . ( 50 Omega )
( mathbf{c} .52 Omega )
D. ( 30 Omega )
12
40 A coil of insulated wire is connected to a
battery. If it is taken to a galvanometer, its pointer is deflected, because
A. induced current is produced in the galvanometer coil
B. the coil acts like a magnet
c. the number of turns in the coil of the galvanometer are changed
D. none of the above
12
41 The magnetic field at a distance x on the axis of a circular coil of radius ( mathrm{R} ) is
( frac{1}{8} ) th of that at the centre.The value of ( x )
is
A ( cdot frac{R}{sqrt{3}} )
в. ( frac{2 R}{sqrt{3}} )
c. ( R sqrt{3} )
D. ( R sqrt{2} )
12
42 A long solenoid of length ( L ) has a mean
diameter ( D . ) It has ( n ) layers of winding of
( N ) turns each. If it carries a current ( I )
the magnetic field at its centre will be.
A. Proportional to ( D )
B. Inversely proportional to ( D )
c. Independent of ( D )
D. Proportional to L.
12
43 A steady current flows in a long wire. It is bent into a circular loop of one turn and the magnetic field at the centre of
the coil is ( B ). If the same wire is bent
into a circular loop of ( n ) turns, the magnetic field at the centre of the coil
is:
A ( cdot frac{B}{n} )
в. ( n B )
( c cdot n B^{2} )
D . ( n^{2} B )
12
44 According to Ampere’s swimming rule, if a man swims along a direction opposite to the direction of the current, south pole of the needle deflects
towards his
12
45 A rectangular loop carrying a current ( i ) is placed in a uniform magnetic field ( B ). The area enclosed by the loop is ( A ). If there are ( n ) turns in the loop, the torque acting on the loop is given by
( mathbf{A} cdot n i(bar{A} times bar{B}) )
в. ( n i(overline{A . bar{B}}) )
( frac{i(bar{A} times bar{B})}{n} )
D. ( frac{i(bar{A} . bar{B})}{n} )
12
46 If a beam of electrons travels in a
straight line in a certain region.Can we say there is no magnetic field?
12
47 In a moving-coil instrument, the coil is suspended in a radial magnetic field instead of a uniform magnetic field This is done to :
A. Increase the sensitivity of the instrument
B. increases the accuracy of the instrument
c. make the instrument compact and protable
D. make its deflection proportinal to current through it
12
48 A current-carrying wire in a magnetic field is subjected to a magnetic force. If the current in the wire is quadrupled. Find out the change in magnetic force acting on the wire?
A. It is quartered
B. It is halved
c. It is unchanged
D. It is doubled
E. It is quadrupled
12
49 In an expt, a beam of electron passes
undeviated through mutually perpendicular elec. and mag fields of
respective strength ( boldsymbol{E}=mathbf{7 . 2} times )
( 10^{6} N C^{-1} ) and ( B=2.4 ) T. The velocity of
the electron is
( mathbf{A} cdot 17.3 times 10^{7} m s^{-1} )
B . ( 3 times 10^{6} m s^{-1} )
c. ( 2 times 10^{6} m s^{-1} )
D. ( 6 times 10^{6} mathrm{ms}^{-1} )
12
50 Two parallel wires carrying current in
the same direction attract each other
because of
A. potential difference between them
B. mutual inductance between them
c. electric forces between them
D. magnetic forces between them
12
51 A conductor ( A B C D E F, ) shaped as
shown, carries a current i. It is placed in
the ( x y ) plane with the ends ( A ) and ( E ) on
the ( x ) -axis. A uniform magnetic field of
magnitude ( B ) exists in the region. The
force acting on it will be :
This question has multiple correct options
A. zero, if ( B ) is in the ( x ) -direction
B. ( lambda B i ) in the ( z ) -direction, if ( B ) is in the ( y ) -direction
C. ( lambda B i ) in the negative ( y ) -direction, if ( B ) is in the ( z- ) direction
D. ( 2 a B i ), if ( B ) is in the ( x ) -direction
12
52 In toroid magnetic field on axis will be
radius ( =0.5 mathrm{cm}, ) current ( =1.5 mathrm{A}, ) turns
( =250, ) permeability ( =700 )
( mathbf{A} cdot 7.5 ) Tesla
B. 10.5 Tesla
c. 4.5 Tesla
D. 15.5 Tesla
12
53 Assertion
When two long parallel wires, hanging freely are connected in series to a battery, they come closer to each other.
Reason
Wires carrying current in opposite direction repel each other.
A. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B. Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
54 Assertion
The magnetic force on the closed loop in fig is zero
Reason
Force (magnetic) on the wire is ( int d F= ) ( int i d vec{l} times vec{B} )
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is
not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
55 Two infinitely long current carrying
conductors ( X ) and ( Y ) are kept parallel to
each other, ( 24 mathrm{cm} ) apart in vacuum
They carry currents of ( 5 mathrm{A} ) and ( 7 mathrm{A} ) respectively, in the same direction, as shown in Figure above. Find the position
of a neutral point, i.e. a point where
resultant magnetic flux density is zero.
(Ignore earth’s magnetic field)
12
56 A wire is lying horizontally in the north south direction and there is a horizontal
magnetic field pointing towards the east. Some positive charges in the wire move north and an equal number of
negative charges move south. The direction of force on the wire will be :
A. East
B. Down, into the page.
c. Up, out of the page
D. west
12
57 Two long straight wires of length ( l ) lie parallel to one another and carry currents opposite to one another of
magnitudes ( i_{1} ) and ( i_{2} ) respectively.
The force experienced by each of the straight wires is ( (r ) is the distance of
their separation)
A . repulsive and equal to ( left(mu_{0} / 2 piright)left(i_{1} i_{2} l / rright) )
B. attractive and equal to ( ( left.mu_{0} / 2 piright)left(i_{1} i_{2} l^{2} / rright) )
c. repulsive and equal to ( left(mu_{0} / 2 piright)left(i_{1} i_{2} l^{2} / rright) )
D. attractive and equal to ( left(mu_{0} / 2 piright)left(i_{1} i_{2} l / rright) )
12
58 A conducting circular loop of radius carries a constant current i. It is placed in a uniform mangetic field ( vec{B}_{0} ) such
that ( vec{B}_{0} ) is perpendicular to the plane of the loop. The magnetic force acting on the loop is
A . ir ( B_{0} )
В . ( 2 pi ) ir ( B_{0} )
c. zero
( mathbf{D} cdot pi ) ir ( B_{0} )
12
59 Write Biot-Savart law.
Write the path of motion of an electron
when it enters in magnetic field at
(a) perpendicular
(b) an angle ( boldsymbol{theta} )
12
60 A magnet of moment ( 4 mathrm{Am}^{2} ) is kept
suspended in a magnetic field of induction ( 5 times 10^{-5} T . ) The workdone in
rotating it through ( 180^{0} ) is
( mathbf{A} cdot 4 times 10^{-4} J )
В. ( 5 times 10^{-4} J )
c. ( 2 times 10^{-4} J )
D. ( 10^{-4} J )
12
61 Electrons move at right angles to a magnetic field of ( 0.03 mathrm{T} ) and enter with a velocity ( 9 times 10^{7} m / s . ) The value of e ( / mathrm{m} )
will be: (Given radius of circular path =
( 1.764 mathrm{cm} )
A ( cdot 1.7 times 10^{11} mathrm{Ckg}^{-1} )
В . ( 2 times 10^{11} mathrm{Ckg}^{-} )
c. ( 2.5 times 10^{11} mathrm{Ckg}^{-1} )
D. none of these
12
62 The above figure shows a toroidal
solenoid whose cross-section is
rectangular. Find the magnetic flux (in ( mu W b) ) through this cross-section if the
current through the winding equals ( I=1.7 A ) the total number of turns is
( N=1000, ) the ratio of the outside
diameter to the inside one is ( eta=1.6 )
and the height is equal to ( h=5.0 mathrm{cm} )
12
63 An electric current runs
counterclockwise in a rectangular loop around the outside edge of the page which lies flat on your table. A uniform magnetic field is then turned on directed parallel to the page from the top to bottom. The magnetic force on the page will cause:
A. the left edge to lift up
B. the right edge to lift up
c. the top edge to lift up
D. the bottom edge to lift up
12
64 Assertion
A charged particle is moving in a
circular path under the action of
uniform magnetic field as shown in fig.
During motion kinetic energy of
charged particle is constant.
Reason
During the motion, magnetic force
acting on the particle is perpendicular
to instantaneous velocity.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is
not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
65 A magnetic needle lying parallel to a magnetic field requires W units of work
to turn it through ( 60^{0} ). The torque needed to maintain the needle in this
position will be:
A ( cdot sqrt{3} mathrm{W} )
B. ( W )
c. ( sqrt{3 / 2} mathrm{W} )
D. 2w
12
66 Two long and parallel straight wires ( A ) and B are carrying currents of 4 A and 7 A in the same direction are separated by a distance of ( 5 mathrm{cm} . ) The force acting
on an ( 8 mathrm{cm} ) section of wire ( mathrm{A} ) is:
A ( cdot 3 times 10^{-6} N )
B . ( 6 times 10^{-6} N )
c. ( 9 times 10^{-6} N )
D. ( 12 times 10^{-6} N )
12
67 A tangent galvanometer has 80 turns of wire. The internal and external
diameters of the coil are ( 19 mathrm{cm} ) and
( 21 mathrm{cm} ) respectively. The reduction factor
of the galvanometer at a place where ( boldsymbol{H}=mathbf{0 . 3 2} ) oersted will be (1 oersted ( = )
( mathbf{8 0} boldsymbol{A} / boldsymbol{m}) )
A .0 .0064
B. 0.64
( c cdot 0.064 )
D. None of these
12
68 If the magnetic dipole moment of an atom of diamagnetic material,
paramagnetic material and ferromagnetic material are denoted by
( mu_{d}, mu_{p} ) and ( mu_{f} ) respectively, then
( mathbf{A} cdot mu_{p}=0 ) and ( mu_{f} neq 0 )
B . ( mu_{d} neq 0 ) and ( mu_{p}=0 )
C ( cdot mu_{d} neq 0 ) and ( mu_{f} neq 0 )
D. ( mu_{d}=0 ) and ( mu_{p} neq 0 )
12
69 A particle moving towards south in a
vertically downward magnetic field is
deflected toward the east.What is the
sign of the charge on the particle?
12
70 Two electrons are entering
perpendicularly to the magnetic field. The velocity of one of the electrons is
three times greater than the velocity of
the other electron. Calculate the ratio of
the circular radii of the path followed by
the two electrons?
A. The faster electron has a radius two times larger than the slower electron
B. The faster electron has a radius three times larger than the slower electron
C. The faster electron has a radius eight times larger than the slower electron
D. The faster electron has a radius sixteen times larger than the slower electron
E. The faster electron has a radius sixty-four times larger than the slower electron
12
71 Two tangent galvanometers, which are identical except in their number of turns, are connected in parallel. The ratio of their resistances of the coils is
1 : 3. If the reflection in the two tangents
galvanometers are ( 30^{circ} ) and ( 60^{circ} )
respectively, then the ratio of their number of turns is:
A .2: 3
в. 3: 1
c. 1: 2
D. 1: 6
12
72 An electric current predominantly produce……………… field around it.
A. magnetic
B. electric
c. gravitational
D. all the above
12
73 Sensitivity of a moving coil galvanometer can be increased by:
A. decreasing the number of turn of coil
B. increasing the number of turn of coil
c. decreasing the area of a coil
D. by using a week magnet
12
74 If a current circular loop is placed in a
( x-y ) plane as shown in adjoining
figure and a magnetic field is applied along z-axis, then the loop will
A. Contract
B. Expand
c. Move towards ( -x- ) axis
D. Move towards ( +x- ) axis
12
75 The lateral surface of a long straight
solenoid with ( n ) turns per unit
length experiences a pressure of ( boldsymbol{p}= ) ( frac{1}{x} mu_{0} n^{2} I^{2} ) when a current ( I ) flows
through it. Find ( x )
12
76 A long dielectric cylinder of radius ( boldsymbol{R} ) is
statically polarized so that at all its points the polarization is equal to ( vec{P}= ) ( alpha vec{r}, ) where ( alpha ) is a positive constant, and
( vec{r} ) is the distance from the axis.

The cylinder is set into rotation about
its axis with an angular velocity ( omega . ) Find
the magnetic induction ( B ) at the centre
of the cylinder

12
77 The magnetic moment of current ( (boldsymbol{I}) )
carrying circular coil of radius ( (r) ) and
number of turns ( (n) ) varies as
A ( cdot 1 / r^{2} )
в. ( 1 / r )
( c )
D ( cdot r^{2} )
12
78 A current of i ampere is flowing in an equilateral triangle of side a. The magnetic induction at the centroid will
be?
A ( cdot frac{mu_{i}}{3 sqrt{3} pi a} )
в. ( frac{3 mu_{i}}{2 pi a} )
( ^{mathrm{c}} cdot frac{5 sqrt{2} mu_{i}}{3 pi a} )
D. ( frac{9 mu_{i}}{2 pi a_{i}} )
12
79 State and explain Ampere’s circuital
law.
12
80 What is the magnetic moment of the atom due to the motion of the electron? 12
81 A rectangular loop carrying a current ( boldsymbol{i}_{1} ) is situated near a long straight wire
carrying a steady current ( i_{2} . ) The wire is
parallel to one of the sides of the loop and is in the plane of the loop as shown in the figure. Then the current loop will
A. move away from the wire
B. move towards the wire
c. remain stationary
D. rotate about an axis parallel to the wirce
12
82 A charged particle is shot at an angle ( theta )
to a uniform magnetic field along directed X-axis. Duration its motion
along a helical path, whose pitch is equal to the maximum distance from ( x ) axis, the particle will :
This question has multiple correct options
A. Never move parallel to x-axis
B. ( tan theta=2 / p i )
( mathbf{c} cdot sin theta=1 / p i )
D. ( tan theta=pi )
12
83 A long horizontal wire ( boldsymbol{P} ) carries a
current ( 50 A ). It is rigidly fixed. Another
line wire ( Q ) is placed directly above and
parallel to ( P . ) The weight of wire ( Q ) is
( 0.075 N m^{-1} ) and caries a current of
( 25 A . ) Find the position of wire ( Q ) from ( P ) so that wire to remains suspended due to the magnetic repulsion-
A. ( 3.33 mathrm{mm} )
B. ( 33.3 mathrm{mm} )
c. 334 mm
D. 333 mm
12
84 A light charged particle is resolving in a circle of radius ‘r’ in electrostatic
attraction of a static heavy particle with opposite charge. How does the magnetic field ‘B’ at the centre of the circle due to the moving charge depend
on ‘r’?
A ( cdot B propto frac{1}{r} )
в. ( B propto frac{1}{r^{2}} )
c. ( _{B} propto frac{1}{r^{frac{3}{2}}} )
D. ( B propto frac{1}{r^{frac{5}{2}}} )
12
85 Answer the following Questions:
Name and state the rule to determine
the direction of a force experienced by a straight conductor carrying placed in a magnetic field which is perpendicular to it.
12
86 Assertion
In meter bridge experiment, a high resistance is always connected in
series with a galvanometer.
Reason
As resistance increases current
through the circuit increases.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
87 A wire of a length 2 m carrying a
current of ( 1 mathrm{A} ) is bend to form a circle.
The magnetic moment of the coil is
( left(i n A-m^{2}right): )
(a) ( 1 / pi )
(b) ( pi / 2 )
12
88 Two thin, long, parallel wires, separated by a distance ‘d’ carry a current of ‘i’ A in
the same direction. They will
A ( . ) repel each other with a force of ( mu_{0} i^{2} /(2 pi d) )
B. attract each other with a force of ( mu_{0} i^{2} /(2 pi d) )
C . repel each other with a force of ( mu_{0} i^{2} /left(2 pi r d^{2}right) )
D. attract each other with a force of ( mu_{0} i^{2} /left(2 pi d^{2}right) )
12
89 Assertion
If a charged particle enters from outside at right angles in uniform
magnetic field.The maximum time spent in magnetic field may be ( frac{pi m}{B q} )
Reason

It can complete only semi-circle in the magnetic field.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect

12
90 A uniform conduction wire of length
( 10 g ) and resistance ( R ) is wound up into
four turns as a current carrying coil in
the shape of equilateral triangle of side
( a . ) If current ( I ) is flowing through the coil
then the magnetic moment of the coil is
A ( cdot frac{sqrt{3}}{2} a^{2} I )
B. ( frac{a^{2} I}{sqrt{3}} )
c. ( sqrt{3} a^{2} I )
D. ( frac{2 a^{2} I}{sqrt{3}} )
12
91 When current flows in a wire, it creates field around it. Fill in the
blank:
A . gravitational
B. magnetic
c. repulsive
D. attractive
12
92 Two long conductors, separated by a
distance d carry current ( I_{1} ) and ( I_{2} ) in the
same direction. They exert a force ( F ) on
each other. Now the current in one of
them is increased to two times and its
direction is reversed. the distance is
also increased to 3 d. The new value of
the force between them is
A ( cdot-frac{2 F}{3} )
B. ( frac{F}{3} )
c. ( -2 F )
D. ( -frac{F}{3} )
12
93 For given current distribution, each
infinite length wire produces magnetic
field ( B ) at origin their resultant
magnetic field at origin ( boldsymbol{O} ) is:
A . ( 4 B )
В. ( sqrt{2} B )
( c cdot 2 sqrt{2} B )
D. zero
12
94 A square of side ( 2.0 mathrm{m} ) is placed in a
uniform magnetic field ( mathbf{B}=mathbf{2 . 0} mathbf{T} ) in a
direction perpendicular to the plane of the square inwards. Equal current
( mathbf{i}=mathbf{3 . 0 A} ) is flowing in the directions shown in figure. Find the magnitude of the magnetic force on the loop.
12
95 Assertion
If the current in a solenoid is reversed in
direction while keeping the same magnitude, the magnetic field energy stored in the solenoid decreases.
Reason

Magnetic field energy density is proportional to square of current
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct

12
96 In which of the following situations, the magnetic field can accelerate a charge particle at rest?
I. When the magnetic field is uniform with respect to time as well as position
11. When the magnetic field is time varying but uniform w.r.t position
III. When the magnetic field is time independent but position dependent.
A. I, II and II
B. III only
c. ॥ only
D. None of these
12
97 What is the strength of the electric field in the velocity selector?
A ( cdot 2 times 10^{5} N C^{-1} )
B . ( 2 times 10^{3} N C^{-1} )
c. ( 2 times 10^{6} N C^{-1} )
D. ( 2 times 10^{4} N C^{-1} )
12
98 Choose the correct statement.
A. Polar molecules have permanent electric dipole moment
B. ( C O_{2} ) molecule is a polar molecule
( mathrm{C} cdot mathrm{H}_{2} mathrm{O} ) is a non-polar molecule
” The dipole field at large distances falls of as ( frac{1}{r^{2}} )
E. The dipole moment is a scalar quantity
12
99 A magnetic field directed along ( Z ) axis
varies as ( boldsymbol{B}=boldsymbol{B}_{0} boldsymbol{x} / boldsymbol{a}, ) where ( boldsymbol{B}_{0}= )
2 tesla and ( a=1 m . ) A conducting
square loop of side ( ell=frac{1}{2} m ) is placed
with its edges parallel to ( X ) and ( Y ) axes. If
the loop is made to move with a
constant velocity ( v_{0}=6 m / s ) directed
along ( X ) axis, the induced emf (in volts) in the loop is :
12
100 A straight wire of finite length carrying
current I subtends an angle of ( 60^{circ} ) at
point ( P ) as shown. The magnetic field at
P is:
( ^{mathrm{A}} cdot frac{mu_{0} I}{2 sqrt{3} pi x} )
B. ( frac{mu_{0} I}{2 pi x} )
c. ( frac{sqrt{3} mu_{0} I}{2 pi x} )
D. ( frac{mu_{0} I}{3 sqrt{3} pi x} )
12
101 When two infinitely long parallel wires
separated by a distance of ( 1 m, ) each carry a current of ( 3 A ), the force in newton/metre length experienced by each will be, ( left(operatorname{given} mu_{0}=4 pi times 10^{-7} mathrm{S.I}right. )
Units).
A. ( 2 times 10^{-7} )
B. ( 3 times 10^{-7} )
c ( .6 times 10^{-7} )
D. ( 18 times 10^{-7} )
12
102 How will two parallel beams of electron behave while moving in the same direction?
A. repel each other
B. attract each other
c. not interact with each other
D. annihilate each other
12
103 Assertion
A charge, whether stationary or in motion produces a magnetic field around it.
Reason
Moving charges produce only electric field in the surrounding space.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
104 A negatively charged particle is moving through a magnetic field as pictured
below.
What is the direction of the force on the
particle due to the magnetic field at the instant in the picture?
West
A. North
B. west
c. East
D. Up
E. Down
12
105 An arrangement with a pair of quarter circular coils of radii ( r ) and ( R ) with a
common centre ( C ) and carrying a
current I is shown.
The permeability of free space is ( mu_{0} . ) The
magnetic field at ( mathrm{C} ) is :
A ( cdot mu_{0} I(1 / r-1 / R) / 8 ) into the page
B. ( mu_{0} I(1 / r-1 / R) / 8 ) out the page
C. ( mu_{0}(1 / r+1 / R) / 8 ) into the page
D・ ( mu_{0}(1 / r+1 / R) / 8 ) out the page
12
106 topp
Q туре your question
ranges, of ( 0-2 V, 0-10 V ) and 0
( 20 V ). The appropriate circuit to do so is
A ( cdot R_{1}=1900 Omega )
( R_{2}=9900 Omega )
( R_{3}=19900 Omega )
B . ( R_{1}=2000 Omega )
( R_{2}=8000 Omega )
( R_{3}=10000 Omega )
c. ( R_{1}=19900 Omega )
( R_{2}=9900 Omega )
( R_{3}=1900 Omega )
D. ( R_{1}=1900 Omega )
( R_{2}=8000 Omega )
( R_{3}=10000 Omega )
12
107 Assertion
Increasing the current sensitivity of a galvanometer necessarily increases the voltage sensitivity.
Reason
Voltage sensitivity is inversely proportional to current sensitivity.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
108 A horizontal overhead power line is at a height of ( 5 ~ m ) from the ground and carries a current of ( 100 A ) from east to
west. The magnetic field directly below it on the ground is
A ( cdot 2.5 times 10^{-6} T ) eastward
B . ( 4 times 10^{-6} T ) eastward
c. ( 5 times 10^{6} ) southward
D. ( 2 times 10^{-6} ) westward
12
109 The resultant magnetic moment due to two currents carrying concentric coils of radius ( r, ) mutually perpendicular to
each other will be
A. ( sqrt{2} i )
B. ( sqrt{2} i pi r^{2} )
( mathbf{c} cdot 2 pi r^{2} )
D. ( sqrt{2} i r^{2} )
12
110 Q Type your question-
than Segment ( 2, ) but both segments are
centered on point ( P )

The segments are connected by straight
wires as shown, and an unseen source
of EMF creates a constant
counterclockwise current in the wire.
Which wire segment creates a stronger
magnetic field at point P?
A. segment 1 creates stronger magnetic field because Segment 1 is longer
B. Segment 2 creates stronger magnetic field becaus Segment 2 is closer
C. Both segments create the same strength magnetic field because both segments have the same angle
D. Both segments create the same strength magnetic field because both segments have the

12
111 A current of ( 2 A ) is flowing through a
circular coil of radius ( 10 mathrm{cm} ) containing 100 turns. The magnetic flux density at the centre of the coil is ( left(operatorname{in} W b / m^{2}right) )
В. ( 1.26 times 10^{-2} )
c. ( 1.26 times 10^{-4} )
D. ( 1.26 times 10^{-5} )
12
112 A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10 – divisions per milliampere and
voltage sensitivity is 2 divisions per millivolt. In order that
each division reads 1 volt, the resistence in ohms needed to be
connected in series with the coil will be
A . 103
B . 10
( c .9995 )
D. 99995
12
113 On connecting a battery to the two corners of a diagonal of a square
conductor frame of side ( a ) the
magnitude of the magnetic field at the centre will be:
A . zero
в. ( frac{mu_{0}}{pi a} )
c. ( frac{2 mu_{0}}{pi a} )
D. ( frac{4 mu_{0}}{pi a} )
12
114 toppr 5
Q Type your question
( A )
B.
( c )
( D )
( E )
12
115 Charged particle (charge= ( q ; ) mass ( = )
( boldsymbol{m} ) ) is rotating in a circle of radius ( boldsymbol{R} )
with uniform speed ( V ), Ratio of its magnetic moment ( (mu) ) to the angular
momentum ( (L) ) is
( ^{mathrm{A}} cdot frac{q}{2 m} )
в. ( frac{q}{m} )
c. ( frac{q}{4 m} )
D. ( frac{2 q}{m} )
12
116 If a charged particle kept at rest experiences an electromagnetic force This question has multiple correct options
A. the electric field must not be zero
B. the magnetic field must not be zero
c. the electric field may or may not be zero
D. the magnetic field may or may not be zero
12
117 The region between ( boldsymbol{x}=mathbf{0} ) and ( boldsymbol{x}=boldsymbol{L} ) is
filled with uniform, steady magnetic field ( B_{0} hat{k} . ) A particle of mass ( m, ) positive charge ( q ) and velocity ( v_{0} hat{i} ) travels along
x-axis and enters the region of magnetic field. Neglect gravity throughout the question. The field now
extends up to ( x=2.1 L ) If the time
spent by the particle in the magnetic field is ( T=frac{pi m}{X times q B_{0}} . ) Find ( X ? )
12
118 The following diagram in figure shows a fixed coil of several turns connected to a
centre zero galvanometer ( G ) and ( a )
magnet NS which can move in the direction shown in the diagram. How
would the observation alter if a more
powerful magnet is used?
12
119 Using Biot-Savart’s law, obtain an expression for magnetic field at a distance ( r ) metre from an infinitely long
wire carrying a current of ( i ) ampere.
12
120 A vertical wire kept in Z-X plane carries
a current from ( Q ) to ( P ) (see figure.). The
magnetic field due to current will have
the direction at the origin 0 along
( A cdot O x )
B. ox
( c cdot ) or
D. or
12
121 Cathode rays are moving between the
poles of a magnet. Due to the effect of magnetic field of magnet:
A. velocity of rays increase
B. velocity of rays decrease
c. rays deflected towards south pole
D. rays deflected in upward direction and perpendicular to the plane of the paper
12
122 A particle of charge ( q ) and mass ( m ) starts moving from origin under the action of an electric field ( vec{E}=E_{0} vec{i} ) and magnetic field ( vec{B}=B_{0} vec{k} ). Its velocity at
( (x, 3,0) ) is ( (4 i+3 i), ) the value of ( x ) is:
A ( cdot frac{36 E_{o} B_{0}}{q m} )
В. ( frac{25 m}{2 q E_{0}} )
c. ( frac{10 m}{q E_{o}} )
D. ( frac{25 E_{0} B_{0}}{m} )
12
123 The angle made by orbital angular momentum of electron with the
direction of the orbital magnetic
moment is?
A ( cdot 120^{circ} )
B. ( 60^{circ} )
( c cdot 180^{circ} )
D. ( 90^{circ} )
12
124 The torque and magnetic potential energy of a magnetic dipole in most stable position in a uniform magnetic field( ( bar{B} ) ) having magnetic moment ( (bar{m}) ) will be.
A. – mB, zero
B. mB, zero
c. zero, mB
D. Zero, -mB
12
125 An otherwise infinite, straight wire has
two concentric loops of radii ( a ) and ( b )
carrying equal currents in opposite directions as shown in figure. The
magnetic field at the common center is
zero for:
( ^{mathrm{A}} cdot frac{a}{b}=frac{pi-1}{pi} )
B. ( frac{a}{b}=frac{pi}{pi+1} )
c. ( frac{a}{b}=frac{pi-1}{pi+1} )
D. ( frac{a}{b}=frac{pi+1}{pi-1} )
12
126 The least value of magnetic moment
(where ( m ) is the mass of the electron, ( e ) is
the charge of electron) is :
A ( cdot frac{e h}{m} )
в. ( frac{e h}{4 pi m} )
c. ( frac{2 e h}{pi m} )
D. ( frac{e h}{pi m} )
12
127 A current of i amp flows in a loop having circular arc of radius ( r ) subtending an
angle ( theta ) as shown in the figure. The
magnetic field at the centre of the circle
is:
A ( cdot frac{mu_{0} i}{4 pi r} )
B. ( left(frac{mu_{0} i}{4 r}right) sin theta )
c. ( left(frac{2 mu_{0} i}{2 r}right) sin theta )
D. ( left(frac{mu_{0} i}{4 pi r}right) sin theta )
12
128 The work done in rotating the magnet from the direction of uniform field to the
opposite direction to the field is ( W ). The
work done in rotating the magnet from the field direction to half the maximum
couple position is :
A ( .2 ~ W )
B. ( frac{sqrt{3} W}{2} )
c. ( frac{W}{4}(2-sqrt{3}) )
D. ( frac{W}{4}(1-sqrt{3}) )
12
129 Potential energy of a bar magnet of magnetic moment ( M ) placed in a magnetic field of induction ( B ) Such that
it makes an angle ( theta ) with the direction
of ( B ) is ( left(operatorname{take} theta=90^{circ} ) as datum) right.
( mathbf{A} cdot-M B sin theta )
B. ( -M B cos theta )
c. ( M B(1-cos theta) )
D. ( M B(1+cos theta) )
12
130 The gyromagnetic ratio of an electron in
sodium atom is:
A. depending upon the atomic number of the atom
B. depending upon the shell number of the atom
C. independent of that orbit it is in
D. having positive value
12
131 Define watt. Write down an equation linking watts, volts and amperes. 12
132 An electron is projected so that it crosses three different regions of space
as shown. if ( B_{1}, B_{2} ) and ( B_{3} ) are the
magnetic field in the region,then:
( A cdot B_{1} ) is inward
B. ( B_{2} ) is outward
( c cdot B_{3} ) is inward
D. All of these
12
133 A current of 1 amp is flowing in the
sides of an equilateral triangle of side
( 4.5 times 10^{-2} mathrm{m} . ) Find the magnetic field at
the centroid of triangle.
12
134 State Ampere’s circuital law. Obtain an expression for magnetic induction along the axis of toroid. 12
135 Match the following and find the correct
pairs:
List List II
(a) Fleming’s
(e) Direction of induced current left hand rule
(b) Right hand
(f) Magnitude and direction of thumb rule ( quad ) magnetic induction
(c) Biot-Savart
(g) Direction of force due to law ( quad ) magnetic induction
(d) Fleming’s
(h) Direction of magnetic lines right hand rule due to current
( A cdot a-g, b-e, c-f, d-h )
B. ( a-g, b-h, c-f, d-e )
( mathbf{C} cdot a-f, b-h, c-g, d-e )
D. a-h, b-g, c-e, d-f
12
136 A rectangular coil placed in a region having a uniform magnetic field perpendicular to the plane of the coil. An
e.m.f. will not be induced in the coil if
the:
A. magnetic field increases uniformly
B. coil is rotated about an axis perpendicular to the plans of the coil and passing through its centre 0 , the coil remaining in the same plane
c. coil is routed about the axis ( 0 x )
12
137 Q Type your question.
( operatorname{arm} mathrm{PQ}, ) which remains hinged along a
horizontal line taken as the y-axis. A uniform magnetic field ( overrightarrow{boldsymbol{B}}=(mathbf{3} hat{mathbf{i}}+ )
( 4 hat{k}) B_{0} ) exists in the region. The loop is
held in the ( x ) -y plane and a current lis passed through it. The loop is now released and is found to stay in the
horizontal position in equilibrium.
(a) What is the direction of the current
n PQ?
(b) Find the magnetic force on the arm
RS.
(c) Find the expression for I in terms of
( B_{0}, ) a b and ( m )
12
138 A metal wire of mass ( m ) slides without
friction on two rails at distance ( d ) apart.
The track is in a vertical uniform field of
induction ( vec{B} ). A constant current ( vec{i} ) flows
along one rail across the wire and back down the other rail the velocity of the wire as a function of time, assuming it to be at rest initially.
A ( cdot frac{B i d}{m} )
в. ( frac{B i d t}{m} )
c. ( frac{m}{text { Bidt }} )
D. None of the above
12
139 A galvanometer having a coil resistance of ( 60 Omega ) shows full scale deflection when a current of 1.0 amp passes through it. It can be converted into an ammeter to
read currents upto 5.0 amp by :
A. Putting in parallel a resistance of ( 15 Omega )
B. Putting in parallel a resistance of ( 240 Omega )
c. Putting in series a resistance of ( 15 Omega )
D. Putting in series a resistance of ( 240 Omega )
12
140 Which of the following is a source of magnetic field?
A. isolated Magnetic pole
B. static electric charge
c. current loop
D. moving light source
12
141 The earth’s magnetic field at a given point is ( 0.5 times 10^{-5} W b m^{-2} . ) This field is
to be annulled by magnetic induction at the centre of a circular conducting loop
of radius ( 5.0 mathrm{cm} . ) The current required to
be flown in the loop is nearly
в. ( 0.4 A )
( c .4 A )
D. ( 40 A )
12
142 A moving coil galvanometer has a coil with 175 turns and area ( 1 mathrm{cm}^{2} ). It uses a
torsion band of torsion constant ( 10^{-6} mathrm{N} )
( mathrm{m} / mathrm{rad} . ) The coil is placed in a magnetic field B parallel to its plane. The coil
deflects by ( 1^{circ} ) for a current of ( 1 mathrm{mA} ). The value of ( mathrm{B}(text { in } text { Telsa }) ) is approximately.
A ( cdot 10^{-3} )
B . ( 10^{-1} )
( c cdot 10^{-4} )
D. ( 10^{-2} )
12
143 At very close point on the axis of a current carrying circular coil ( ( boldsymbol{x}<<< )
( R ) ) of radius ( ^{prime} R^{prime}, ) the value of magnetic
field decreases by a fraction of ( 5 % ) with respect to centre value. The position of the point from the centre of the coil is :-
A ( cdot frac{R}{sqrt{10}} )
в. ( frac{R}{sqrt{30}} )
c. ( frac{R}{sqrt{50}} )
D. ( frac{R}{sqrt{150}} )
12
144 The force between two current carrying wires is due to the force.
A. magnetic
B. electric
c. centripetal
D. centrifugal
12
145 Two current carrying loops having ( N_{1} )
turns and ( N_{2} ) turns respectively both
carrying a current equal to ( I ) in the same direction, are placed inside a magnetic field ( B ). If the radii of both
loops are in the ratio 1: 3 then what will
be the ratio of the potential energy of loops in that magnetic field?
A ( cdot frac{N_{1}}{N_{2}} )
B. ( frac{2 N_{1}}{N_{2}} )
c. ( frac{N_{1}}{3 N_{2}} )
D. ( frac{N_{1}}{9 N_{2}} )
12
146 The magnetic tield at the centre ot a
circular coil of radius ( r ) is ( pi ) times that
due to a long straight wire at a distance
r from it, for equal currents. Figure
shows three cases. In all cases the
circular path has radius r and straight
ones are infinitely long. For same
current the ( mathrm{B} ) field at the centre ( mathrm{P} ) in
cases 1,2,3 has the ratio:
( ^{mathbf{A}} cdot-left(frac{pi}{4}+frac{1}{2}right):left(frac{pi}{2}right):left(frac{3 pi}{4}-frac{1}{2}right) )
B ( cdotleft(-frac{pi}{2}+1right):left(frac{pi}{2}+1right):left(frac{3 pi}{4}+frac{1}{2}right) )
( mathbf{C} cdot-frac{pi}{2}: frac{pi}{2}: frac{3 pi}{4} )
D ( cdotleft(-frac{pi}{2}-1right):left(frac{pi}{2}-frac{1}{4}right):left(frac{3 pi}{4}+frac{1}{2}right) )
12
147 Force between the two parallel wires
carrying currents has been used to
define
A. ampere
B. coulomb
c. volt
D. watt
12
148 Two wires each carrying a steady
current I are shown in four
configurations in Column I. Some of the resulting effects are described in Column II. Match the
statements in Column I with the
statements in Column II and indicate
your
answer by darkening appropriate bubbles in the ( 4 mathrm{X} 4 ) matrix given in the
ORS.
12
149 If a long straight wire carries a current
of ( 40 mathrm{A} ), then the magnitude of the field B at a point ( 15 mathrm{cm} ) away from the wire is:
A ( cdot 5.34 times 10^{5} mathrm{T} )
B. ( 8.34 times 10^{5} mathrm{T} )
c. ( 9.6 times 10^{5} mathrm{T} )
D . 10.2 ( times 10^{5} ) न
12
150 In a mass spectrometer used for
measuring the masses of ions, the ions are initially accelerated by an electric potential ( V ) and then made to follow
semicircular paths of radius ( R ) using a
magnetic field ( B . ) If ( V ) and ( B ) are kept
constant, the ratio ( left(frac{operatorname{charg} text { on the ion }}{text { mass of the ion }}right) ) will be proportional to
A ( cdot frac{1}{R} )
в. ( frac{1}{R^{2}} )
c. ( R^{2} )
D. ( R )
12
151 Two circular coils 1 and 2 are made from
the same wire but the radius of 1st coil
is twice that of the 2 nd coil. What
potential difference in volts should be
applied across them so that the magnetic magnetic field at the centres is the same
A. 4 times of first coil
B. 6 times of first coil
c. 2 times of first coil
D. 3 times of first coil
12
152 A hypothetical magnetic field existing in a region is given by ( vec{B}=B_{0} vec{e}_{r}, ) where
( vec{e}_{r} ) denotes the unit vector along the
radial direction. A circular loop of radius ( alpha, ) carrying a current ( i, ) is placed
with its plane parallel to ( X-Y ) plane
and the centre at ( (0,0, d) . ) Find the magnitude of the magnetic force acting on the loop.
A ( cdot frac{i 2 pi b_{o} a^{3}}{sqrt{a^{2}+d^{4}}} )
B. ( frac{i 2 d_{o} a^{2}}{sqrt{a^{2}+b^{2}}} )
c. ( frac{pi b_{o} a^{2}}{sqrt{a+d^{2}}} )
D. ( frac{i 2 pi b_{a} a^{2}}{sqrt{a^{2}+d^{2}}} )
12
153 A rectangular loop carrying a current ( i )
is situated near a long straight wire such that the wire is parallel to one of
the sides of the loop and is in the plane
of the loop. If steady current lis established in the wire as shown in fig.
the loop will
A. rotate about an axis parallel to the wire
B. move away from the wire
c. move toward the wire
D. remain stationary
12
154 A proton, deutron and an ( alpha ) -particle enter a magnetic field perpendicular to field with same velocity. What is the ratio of the radii of circular paths?
A .1: 2: 2
B. 2:1:1
c. 1: 1: 2
D. 1: 2: 1
12
155 The figure shows a circuit containing a
coil wound over a long and hollow thin
tube. Mention two methods to increase
the strength of the magnetic field
inside the coil.
12
156 The magnetic moment of a thin round loop with current, if the radius of the loop is equal to ( R=100 m m ) and the
magnetic field at its centre is equal to ( B=6.0 mu T, ) is ( 30 times 10^{-x} A-m^{2} ). Find
the value of ( x )
12
157 A current in the windings on a toroid is
2 A. There are 400 turns and the mean
circumferential length is ( 40 mathrm{cm} . ) If the magnetic field inside is ( 1 T ), the relative permeability is :
A . 200
B. 2500
( c cdot 400 )
D. 150
12
158 You are sitting in a room in which uniform magnetic field is present in vertically downward direction. When an
electron is projected in horizontal direction, it will be moving in circular path with constant speed
A. clockwise in vertical plane
B. clockwise in horizontal plane
c. anticlockwise in vertical plane
D. anticlockwise in horizontal plane
12
159 An ( alpha ) -particle is moving along a circle of
radius ( R ) with a constant angular
velocity ( omega . ) Point ( A ) lies in the same
plane at a distance ( 2 R ) from the center.
Point ( A ) records magnetic field
produced by the ( alpha ) -particle. If the
minimum time interval between
successive times at which ( A ) records
zero magnetic field is ( t ), the angular
speed ( omega, ) in terms of ( t, ) is :
A. ( frac{2 pi}{t} )
в. ( frac{2 pi}{3 t} )
c. ( frac{pi}{3 t} )
D.
12
160 An electric charge in uniform motion produces:
A. An electric field only
B. A magnetic field only
c. Both electric and magnetic fields
D. No such field at all
12
161 (a) Deduce an expression for the frequency of revolution of a charged particle in a magnetic field and show that it is independent of velocity or energy of the particle.
(b) Draw a schematic sketch of a
cylotron. Explain, giving the essential details of its construction, how it is used to accelerate the charged
particles.
12
162 In a hydrogen atom, the electron moves
in an orbit of radius ( 0.5 A^{circ} ) making ( 10^{16} ) revolution per second. The magnetic moment associated with the orbital
motion of the electron is ( A m^{2} )
A. ( 1.602 times 10^{-19} )
?
В. ( 1.256 times 10^{-22} )
c. ( 1.67 times 10^{-2} )
D. ( 1.256 times 10^{-23} )
12
163 There will be no force experienced if
A. two parallel wires carry currents in the same direction
B. two parallel wires carry currents in the opposite direction
C. a positive charge is projected between the pole pieces of a bar magnet
D. a positive charge is projected along the axis of a solenoid carrying current
12
164 In a moving coil galvanometer, the magnetic pole pieces are made cylindrical and a soft iron core is placed at the centre of the coil,the purpose for doing so is:
A. to make the magnetic field strong
B. to make the magnetic field strong and radial
c. to make the magnetic field uniform
D. to make the magnetic field strong and uniform
12
165 Instrument that used to measure small
electric currents ?
A. Pipette
B. Manometer
c. Balance
D. Calorimeter
E. Galvanometer
12
166 Which of the following quantities is not affected by a magnetic field?
A. Stationary charge
B. Moving charge
c. change in magnetic flux
D. Current flowing in a conductor
12
167 f current through the conductor Y is reversed in direction, will neutral point lie between ( X ) and ( Y ), to the left of ( X ) or to
the right of Y?
12
168 Two equal electric currents are flowing perpendicular to each other as shown in figure. AB and CD are perpendicular to each other and symmetrically placed with respect to the currents. Where do
we expect the resultant magnetic field to be zero?
( A cdot ) on ( A B )
B. on CD
( c ). on both ( A B & ) CD
D. on both OD & BO
12
169 The relation between voltage sensitivity
( sigma_{v} ) and the current sensitivity ( sigma_{i} ) of ( a )
moving coil galvanometer is (Given that
( G ) is the resistance of the
galvanometer)
A ( cdot sigma_{v}=G sigma_{i} )
в. ( sigma_{v}=frac{sigma_{i}}{G} )
( mathbf{c} cdot sigma_{v} sigma_{i}=G )
D. ( sigma_{v} sigma_{i}=frac{1}{G} )
12
170 Two long thin wires ( A B C ) and ( D E F ) are
arranged as shown in figure. They carry
equal current ( I ) as shown. The
magnitude of the magnetic field at ( O ) is
A. zero
в. ( mu_{0} I / 4 pi a )
c. ( mu_{0} I / 2 pi a )
D. ( mu_{0} I / 2 sqrt{2} pi a )
12
171 An infinitely long straight non-magnetic conducting wire of radius a carries a ( d c )
current I. The magnetic field ( B ), at a distance ( r(r<a) ) from axis of the wire
is:
A ( cdot frac{mu_{0} I}{2 pi a} )
в. ( frac{mu_{0} I r}{2 pi a^{2}} )
c. ( frac{2 mu_{0} I r}{pi a^{2}} )
D. ( frac{mu_{0} I r^{2}}{2 pi a^{3}} )
12
172 How does a solenoid behave like a
magnet? Can you determine the north
and south poles of a current-carrying
solenoid with the help of a bar magnet?? Explain.
12
173 A proton and an ( alpha ) -particle enter in a
uniform magnetic field perpendicular to it with same speed. The ratio of time periods of both particle ( square frac{T_{p}}{T_{alpha}} ) 回 will be
( A cdot 1: 2 )
B. 1:3
c. 2:
D. 3:
12
174 Consider the circular loop having
current ( i ) and with central point ( O . ) The
magnetic field at the central point ( boldsymbol{O} ) is
A ( cdot frac{2 mu_{0} i}{3 pi R} ) acting downward
B. ( frac{5 mu_{0} i}{12 R} ) acting downwaro
c. ( frac{6 mu_{0} i}{11 R} ) acting downwar
D. ( frac{3 mu_{0} i}{7 R} ) acting downwar
12
175 Write the expression for magnetic potential energy of a magnetic dipole kept in a uniform magnetic field and explain the terms. 12
176 Is the magnetic dipole moment a vector or a scalar quantity? Write its unit 12
177 Two galvanometers ( A ) and ( B ) require
( 3 m A ) and ( 6 m A ) respectively, to produce the same deflection of 10 divisions.
Then is,
A. ( A ) is more sensitive than ( B )
B. ( B ) is more sensitive than ( A )
c. ( A ) and ( B ) are equally sensitive
D. Sensitiveness of ( B ) is twice that of ( A )
12
178 A uniformly wound solenoidal coil of
self-inductance ( 1.8 times 10^{-4} mathrm{H} ) and
resistance ( 6 Omega ) is cut into two identical
coils. They are now connected in parallel across a 12 volt battery of negligible resistance. Find the current drawn by the circuit in amp.
12
179 A symmetric star-shaped conducting
wire loop is carrying a steady state
current I as shown the figure. The distance between the diametrically
opposite vertices of the star is ( 4 a . ) The magnitude of the magnetic field at the centre of the loop is
12
180 Three identical long solenoids ( P, Q, R ) are connected to each other as shown in
figure. If the magnetic field at the center of ( boldsymbol{P} ) is ( 2.0 T, ) what would be the
field (in ( T ) ) at the center of ( Q ) ? Assume
that the field due to any solenoid is confined within the volume of that
solenoid only.
12
181 An electron after being accelerated through a potential difference ( 100 boldsymbol{V} )
enters a uniform magnetic field of ( 0.004 T ) perpendicular to its direction of motion. Calculate the radius of the path described by the electrons.
12
182 (a) Define one tesla.
(b) Derive an expression for force experienced by a current carrying straight conductor placed in a magnetic field. How can we find the direction of force?
12
183 Assertion
Force experienced by moving charge
will be maximum if direction of velocity of charge is parallel to applied magnetic field.
Reason
Force on moving charge is independent of direction of applied magnetic field.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
184 The value of relative magnetic
permeability ( left(mu_{r}right) ) for ferromagnetic materials is
A ( cdotleft(mu_{r}=1right) )
В ( cdotleft(mu_{r}>>1right) )
c. ( left(mu_{r}1right) )
12
185 A straight horizontal conducting rod of length ( 0.45 mathrm{m} ) and mass ( 60 mathrm{g} ) is suspended by two vertical wires at its ends. A current of ( 5.0 mathrm{A} ) is set up in the rod through the wires.
(a) What magnetic field should be set up normal to the conductor in order that
the tension in the wires is zero?
(b) What will be the total tension in the wires if the direction of current is
reversed keeping the magnetic field same as before?(Ignore the mass of the wires.) ( g=9.8 m s^{-2} )
12
186 How much length of a very wire is required to obtain a solenoid of length ( I_{0} ) and inductance ( L: )
A ( cdot sqrt{frac{2 pi L l}{mu_{0}}} )
в. ( sqrt{frac{4 pi L l}{mu_{0}^{2}}} )
c. ( sqrt{frac{4 pi L l}{mu_{0}}} )
D. ( sqrt{frac{8 pi L l}{mu_{0}}} )
12
187 When an electric current passes
through a solenoid, the distance between any two adjacent rings of the solenoid
A . decreases
B. increases
c. does not change
D. first increases and then decreases
12
188 A charged particle moving with constant velocity passes through a region of space without any change in its velocity. If ( mathrm{E} ) and ( mathrm{B} ) represent electric and magnetic fields in that region respectively,what is the ( mathrm{E} ) and ( mathrm{B} ) in this space?
A ( . E=0 ) and ( B=0 )
B. ( E=0 ) and ( B neq 0 )
c. ( E neq 0 ) and ( B=0 )
D. ( E neq 0 ) and ( B neq 0 )
12
189 Lis a circular ring made of a uniform
wire. Current enters and leaves the rind
through straight conductors which, if
produced, would have passed through
the centre ( C ) of the ring. The magnetic
field at ( C: )
This question has multiple correct options
A. due to the straight conductors is zero
B. due to the loop is zero
C. due to the loop is proportional to ( theta )
D. due to the loop is proportional to ( (pi-theta) )
12
190 Forces ( vec{F} ) experienced by a particle having charge ( q ) and velocity ( vec{v} ) in a magnetic field B is given by ( overrightarrow{boldsymbol{F}}=mathrm{q}(overrightarrow{boldsymbol{v}} times )
( vec{B} ) ). What is the direction of force acting on electrons (negatively charged particles) falling vertically, at a place where the Earths magnetic field is
horizontal pointing towards North?
A. East
B. west
c. vertically up
D. Vertically down
12
191 The force per unit length between two long straight conductors carrying currents 3 A each in the same direction
and separated by a distance of ( 2.0 mathrm{cm} ) is
A ( cdot 9 times 10^{-7} N / m )
В. ( 9 times 10^{-6} N / m )
c. ( 9 times 10^{-5} N / m )
D. ( 9 times 10^{-4} N / m )
12
192 Pick correct statements from among
the following:
a) Electric field and magnetic field are basically independent
b) Electric field and magnetic field are to aspects of the electromagnetic field
c) Electric field and magnetic field may be produced by charge at rest
d) A moving charge produces both electric and magnetic fields
A. a and b are correct
B. b and d are correct
( c . ) b, cand d are correct
D. a, cand dare correct
12
193 A wire carrying a current of ( 100 A ) is bent into the form of a circle of radius
5cm. The flux density at the centre of
the coil is ( _{-}-_{-}-_{-}-_{-} W b / m^{2} )
begin{tabular}{l}
A ( cdot 12.57 times 10^{-5} ) \
hline
end{tabular}
B . ( 125.7 times 10^{-5} )
c. ( 1.257 times 10^{-5} )
D. ( 1257 times 10^{-5} )
12
194 The torque required to hold a small
circular coil of 10 turns, are ( 1 m m^{2} ) and
carrying a current of ( left[frac{21}{44}right] ) A in the middle
of a long solenoid of ( 10^{3} ) turns/m
carrying a current of ( 2.5 mathrm{A} ), with its axis perpendicular to the axis of the solenoid
is:
A ( .1 .5 times 10^{-6} N m )
в. ( 1.5 times 10^{-8} N m )
c. ( 1.5 times 10^{6} mathrm{Nm} )
D. ( 1.5 times 10^{8} mathrm{Nm} )
12
195 A posıtively chargea partıcle or cnarge
( q^{prime} ) enters in a uniform magnetic field ‘B
directed inward and is deflected a
distance ( boldsymbol{y}_{0} ) after traveling a distance
shown in the figure. Then
the pe
use coos FathER30DAY
( A )
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B.
( c )
D.
( E )
12
196 Two coils ( A ) and ( B ) are placed parallel to
each other at a very small distance apart. The coil ( A ) is connected to an A.C.
supply. ( G ) is a very sensitive
galvanometer.When the key ( K ) is closed.
A. A constant deflection will be observed in the galvanometer for a ( 50 mathrm{Hz} ) supply
B. Small variations will be observed in the galvanometer due to applied voltage of ( 50 mathrm{Hz} )
c. oscillations in the galvanometer may be observed when the input a.c. voltage has a frequency of 1 to ( 2 H z )
D. No variations will be observed in the galvanometer even when the input a.c. voltage has a frequency of 1 to ( 2 mathrm{H} )
12
197 Magnetic lines of force causes
A. The picture on a computer screen
B. Radio reception interference
C. Aurora Borealis
D. V.H.S. films
E. All of these
12
198 Two concentric circular coil of radius
( 20 c m ) and ( 30 c m ) carries current ( 2 A ) and
( 3 A ) respectively in opposite direction
then magnetic field at centre will be :-
A. ( 4 pi times 10^{-7} )
В. ( 2 pi times 10^{-7} )
c. ( 2 times 10^{-7} )
D. 0
12
199 A conducting circular loop of radius carries a constant current I. It is placed in a uniform magnetic field B such that B is perpendicular to the plane of the loop. The magnetic force acting on the loop is
( mathbf{A} cdot ) Вᅵ
В. 2 ( pi ) (ВЮА)
c. zero
D. ( pi ) (ВIR)
12
200 In hydrogen atom the electron is
making ( 6.6 times 10^{15} ) rev/s around the
nucleus of radius 0.53 A. The magnetic field produced at the centre of the orbit is nearly
A. ( 0.12 W b / m^{2} )
в. ( 1.2 mathrm{Wb} / mathrm{m}^{2} )
c. ( 12 W b / m^{2} )
D. ( 120 W b / m^{2} )
12
201 A charged particle accelerated through a potential difference of ( 100 V ) passes through uniform electric and magnetic fields so as to experience no deflection. ( boldsymbol{E}=mathbf{1 5} times mathbf{1 0}^{6} boldsymbol{V} boldsymbol{m}^{-1} ) and ( boldsymbol{B}=mathbf{5} times mathbf{1 0}^{mathbf{3}} boldsymbol{T} )
Then the specific charge ( frac{e}{m} ) is :
A ( cdot 4.5 times 10^{4} mathrm{C} / mathrm{kg} )
В . ( 9 times 10^{7} C / k g )
C ( .4 .5 times 10^{3} C / k g )
D. ( 9 times 10^{5} C / k g )
12
202 An ( alpha ) -particle describes a circular path of radius ( r ) in a magnetic field ( B ). The
radius of the circular path described by the proton of same energy in the same magnetic field is :
A ( cdot frac{r}{2} )
B.
( c cdot sqrt{2} r )
D. ( 2 r )
12
203 A uniform magnetic field ( vec{B}=(3 hat{i}+ )
( 4 hat{j}+hat{k}) ) exists in region of space.
semicircular wire of radius 1 m
carrying current ( 1 A ) having its centre ( operatorname{at}(2,2,0) ) is placed in ( x-y ) plane as
shown in figure. The force on semicircular wire will be
( mathbf{A} cdot sqrt{2}(hat{i}+hat{j}+hat{k}) )
B. ( sqrt{2}(hat{i}-hat{j}+hat{k}) )
( mathbf{c} cdot sqrt{2}(hat{i}+hat{j}-hat{k}) )
D. ( sqrt{2}(-hat{i}+hat{j}+hat{k}) )
12
204 Proton which kinetic energy of ( 1 M e V )
moves from south to north. It gets an
acceleration of ( 10^{12} m / s^{2} ) by an applied
magnetic field (west to east). The value of magnetic field:
(Rest mass of proton is ( left.1.6 times 10^{-27} k gright) )
A. ( 0.071 m T )
B. ( 71 m T )
( c .0 .71 m T )
D. ( 7.1 m T )
12
205 The magnetic field inside the coils of a
toroid of radius ( R ) and ( N ) turns with a
current of ( boldsymbol{I} boldsymbol{A} ) is given by
A ( cdot B=frac{mu_{o} N I}{4 pi R} )
в. ( B=frac{mu_{o} N I}{2 pi R} )
C ( . B=mu_{o} N I )
D. None of these
12
206 Assertion
Magnetic field due to current carrying solenoid is independent of its length
and cross-sectional area.
Reason
The magnetic field inside the solenoid is uniform.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
207 Two identical coils carry equal currents have a common centre and their planes
are at right angles to each other. The ratio of the magnitude of the resultant magnetic field at the centre and the field due to one coil is :
A . 2: 1
B. 1: 2
( mathbf{c} cdot sqrt{2}: 1 )
D. ( 1: sqrt{2} )
12
208 A charged particle is released from rest in a region of steady and uniform electric and magnetic fields where ( mathrm{E} | mathrm{B} ) The particle will follow.
A. circular path
B. Elliptical path
c. Helical path
D. Straight line path
12
209 An electron beam is moving from left to right of the observer and magnetic field is acting vertically upwards. The direction of force acting on electron is
A. towards the observer
B. away from the observer
c. downwards
D. upwards
12
210 toppr
Q Type your question_
this region of space. The correct
arrangement for it to escape
undeviated is :
( mathbf{A} )
( B )
( c )
D.
12
211 In the given figure, what is the
magnetic field at the point ‘0’?
A ( cdot frac{mu_{0} I}{4 pi r}+frac{mu_{0} I}{2 pi r} )
( B cdot frac{mu_{0}}{1 pi} )
C. ( frac{mu_{0} I}{4 r}+frac{mu_{0} I}{4 pi r} )
D. ( frac{mu_{0} I}{4 r}-frac{mu_{0} I}{4 pi r} )
12
212 (A) In tangent galvanometer the circular frame is rotated until the plane of the coil is parallel to magnetic meridian
(B) In tangent galvanometer current through it is related to deflection of needle as
A. A is true, B is false
B. A is false, B is true
c. A & B are true
D. A & B are false
12
213 A solenoid of ( 0.4 m ) length with 500
turns carries a current of ( 3 A . ) A coil of
10 turns and of radius ( 0.01 m ) carries a
current of ( 0.4 A . ) The torque required to hold the coil with its axis at right angles to that of solenoid in the middle point of
it is:
A ( cdot 6 pi^{2} times 10^{-7} N m )
В. ( 3 pi^{2} times 10^{-7} N m )
( mathbf{c} cdot 9 pi^{2} times 10^{-7} N m )
D. ( 12 pi^{2} times 10^{-7} N m )
12
214 A solenoid ( 60 mathrm{cm} ) long and of radius 4.0 cm has 3 layers of windings of 300 turns each. A ( 2.0 mathrm{cm} ) long wire of mass ( 2.5 mathrm{g} ) lies inside the solenoid (near its centre) normal to its axis; both the wire and the axis of the solenoid are in the
horizontal plane. The wire is connected through two leads parallel to
the axis of the solenoid to an
external battery which supplies a current of ( 6.0 mathrm{A} ) in the wire. What value
of current (with appropriate sense of circulation) in the windings of the solenoid can support the weight of the wire? ( g=9.8 m s^{-2} )
12
215 A proton, a deuteron and an a-particle are moving with same momentum in a
uniform magnetic field. The ratio of magnetic forces acting on them will be
A. 1: 1: 2
B. 1: 2: 3
( c cdot 2: 1: 1 )
D. 1: 1: 1
12
216 A proton moving with velocity ( V ) is acted upon by electric field ( boldsymbol{E} ) and
magnetic field ( B ). The proton will move undeflected if
12
217 Two particles having the same momentum enter at right angles into same magnetic field and travel in circular paths of radius ( r_{1} ) and ( r_{2} ). The
ratio of their charges is:
A ( cdot frac{r_{1}}{r_{2}} )
B. ( left(frac{r_{1}}{r_{2}}right)^{1 / 2} )
( ^{c} cdotleft(frac{r_{1}}{r_{2}}right)^{2} )
D. ( left(frac{r_{1}}{r_{2}}right)^{-1} )
12
218 The current sensitivity of a moving coil galvanometer depends on
A. the number of turns in the coil
B. moment of inertia of the coil
c. current sent through galvanometer
D. eddy current in A1 frame
12
219 A charge particle of charge ( q ) is moving
with speed ( v ) in a circle of radius ( R ) as shown in figure. Then the magnetic field at a point on axis of circle at a distance
( x ) from centre is :
A ( cdot frac{mu_{0}}{4 pi} frac{q V}{R^{2}} )
в. ( frac{mu_{0}}{4 pi} frac{q V}{left(R^{2}+x^{2}right)} )
c. ( frac{mu_{0}}{4 pi} frac{q V}{x^{2}} )
D. ( frac{mu_{0}}{4 pi} frac{q V R}{left(R^{2}+x^{2}right)^{3 / 2}} )
12
220 A proton moving with a constant velocity passes through a region of space with out change in its velocity. If ( mathrm{E} ) and ( mathrm{B} ) represent the electric and magnetic fields respectively, this region
may have
A. ( E=0, B neq 0 )
B. ( E neq 0, B=0 )
c. ( E ) and ( B ) both parallel ( $ $ )
D. ( E ) and ( B ) inclined at ( 45^{circ} ) angle
12
221 What is the direction of magnetic field at the centre of a coil carrying current
in anticlockwise direction?
A. Perpendicular to the axis of coil inwards.
B. Perpendicular to the axis of coil outwards
c. Along the axis of coil inwards
D. Along the axis of coil outwards
12
222 Two particles of equal charges after being accelerated through the same potential difference enter in a uniform transverse magnetic field and describe
circular paths of radii ( boldsymbol{R}_{1} ) and ( boldsymbol{R}_{2} . ) Then
the ratio of their respective masses
( left(M_{1} / M_{2}right) ) is
( mathbf{A} cdot R_{1} / R_{2} )
B. ( left(R_{1} / R_{2}right)^{2} )
c. ( left(R_{2} / R_{1}right) )
as
D. ( left(R_{2} / R_{1}right)^{2} )
12
223 Field inside a solenoid is
A. directly proportional to its length
B. directly proportional to current
C. inversely proportional to number of turns
D. inversely proportional to current
12
224 A wire loop formed by joining two semi-
circular wires of radii ( boldsymbol{R}_{1} ) and ( boldsymbol{R}_{2} ) carries
a current as shown in the adjoining
diagram. The magnetic induction at
the center ( boldsymbol{O} ) is
A ( cdot frac{mu_{0} I}{4 R_{1}} )
B. ( frac{mu_{0} I}{4 R} )
c. ( frac{mu_{0} I}{4}left(frac{1}{R_{1}}-frac{1}{R_{2}}right) )
D. ( frac{mu_{0} I}{4}left(frac{1}{R_{1}}+frac{1}{R_{2}}right) )
12
225 The magnetic field due to a circular
wire at its center is:
A. in the plane of wire
B. ( 30^{circ} ) to the plane of wire
C. Perpendicular to the plane of wire
D. none of the above
12
226 A particle of charge ( q ) and mass ( m )
moves in a circular path of radius ( r ) in a
uniform magnetic field ( B ).

The particle is replaced with a particle
of identical charge and mass ( frac{1}{2} m ) The radius of the new circular path the
particle makes is:
A ( cdot frac{1}{4} r )
в. ( frac{1}{2} r )
c. ( r )
D. ( 2 r )
E . ( 4 r )

12
227 By inserting an iron core in a coil carrying current,the strength of its magnetic field will:
A. Increase
B. Decrease
c. Remain same
D. Become zero
12
228 A cyclotron is used to accelerate
protons to a kinetic energy of 5 MeV. If the strength of magnetic field in the
cyclotron is ( 2 T, ) find the radius and the frequency needed for the applied alternating voltage of the cyclotron.
(Given: Velocity of proton ( =3 x )
( left.10^{7} m / sright) )
12
229 (a) What are different losses in
transformer, suggest steps to minimise
the losses in transformer.
(b) State principle and explain the working of transformer
12
230 in the horizontal plane of the circle as shown in the figure. The path
consists of eight arcs with alternating
radii ( r ) and ( 2 r . ) Each segment of arc
subtends equal angle at the common
centre ( P . ) The magnetic field produced
by current path at point ( boldsymbol{P} ) is
A ( cdot frac{3}{8} frac{mu_{0} I}{r} ; ) perpendicular to the plane of the paper and directed inward.
B. ( frac{3}{8} frac{mu_{0} mathrm{I}}{mathrm{r}} ; ) perpendicular to the plane of the paper and directed outward.
C ( cdot frac{1}{8} frac{mu_{0} I}{r} ; ) perpendicular to the plane of the paper and directed inward.
D. ( frac{1}{8} frac{mu_{0} mathrm{I}}{mathrm{r}} ; ) perpendicular to the plane of the paper and directed outward
12
231 Figure shows a cross-section of a long
ribbon of width ( omega ) that is carrying a
uniformly distributed total current ( i ) into the page. Calculate the magnitude and direction of the magnetic field ( vec{B} ) at a point ( P ) in the plane of the ribbon at a distance d from its edge.
[
begin{array}{ll}
P & x times x cdot x times x times x times x \
& d
end{array}
]
12
232 A straight wire carrying a current ( i_{1} )
amp runs along the axis of a circular
current ( i_{2} ) amp. Then the force of
interaction between the two current
carrying conductors is?
( A cdot infty )
B. zero
c. ( frac{mu_{0}}{4 pi} frac{2 i_{1} i_{2}}{r} mathrm{N} / mathrm{m} )
D. ( frac{2 i_{1} i_{2}}{r} mathrm{N} / mathrm{m} )
12
233 The length of conductor ab carrying
current ( I_{2} ) is ( l . ) Find the force acting on it due to a long current carrying conductor
having current ( I_{1} ) as shown in Fig. The
mid-point of wire ab is distance ( x ) apart
from conductor.
12
234 Error in B is
( mathbf{A} cdot pm 0.9 T )
В. ( pm 0.09 m T )
( mathbf{c} . pm 0.9 m T )
D. ±0.097
12
235 A ( 0.5 m ) long solenoid of ( 10 t u r n s / c m )
has area of cross-section ( 1 mathrm{cm}^{2} )
Calculate the voltage induced across its
ends if the current in the solenoid is
charged from ( 1 A ) to ( 2 A ) in ( 0.1 s )
12
236 An electron enters a magnetic field directed to the right, with a velocity toward the bottom of the screen.
What is the direction of force on the
electron?
A. To the left
B. Into the screen
c. To the right
D. Out of the screen
12
237 Two identical wires ( A ) and ( B ), each of
length ( l ), carry the same current ( l ). Wire
( A ) is bent into a circle of radius ( R ) and
wire ( B ) is bent to form a square of side ( a )
If ( B_{A} ) and ( B_{B} ) are the values of
magnetic field at the centres of the circle and square respectively, then the ratio ( frac{B_{A}}{B_{B}} ) is:
A ( cdot frac{pi^{2}}{16 sqrt{2}} )
в. ( frac{pi^{2}}{16} )
c. ( frac{pi^{2}}{8 sqrt{2}} )
D. ( frac{pi^{2}}{8} )
12
238 Assertion
Magnetic field interacts with a moving charge and not with a stationary charge.
Reason

A moving charge produces a magnetic field.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect

12
239 An electron and a proton are projected with same velocity perpendicular to a
magnetic field. Which particle have greater frequency?
12
240 The force between two parallel
conductors, each of length ( 50 m ) and
distant ( 20 mathrm{cm} ) apart, is ( 1 mathrm{N} ). If the
current in one conductor is double than
that in another one, then their values
will respectively be:
( mathbf{A} cdot 100 A ) and ( 200 A )
B. ( 50 A ) and ( 400 A )
c. ( 10 A ) and ( 30 A )
D. ( 5 A ) and ( 25 A )
12
241 A rectangular loop PQRS made from a
uniform wire has length a, width b and mass m. It is free to rotate about the
( operatorname{arm} mathrm{PQ}, ) which remains hinged along a horizontal line taken as the y-axis. Take the vertically upward direction as the zaxis. A uniform magnetic field ( vec{B}= ) ( (3 hat{i}+4 hat{k}) B_{0} ) exists in the region. The
loop is held in the ( x ) -y plane and a current I is passed through it. The loop is now released and is found to stay in
the horizontal position in equilibrium. Find the magnetic force on the arm RS.
12
242 A conductor AB of length ( l ) carrying a
current ( i ) is placed perpendicular to a
long straight conductor XY carrying a
current ( I ) as shown. The force on ( A B ) will
be :
A ( cdot frac{mu_{0} l i}{2 pi} log 2 )
B ( cdot frac{mu_{0} l i}{2 pi} log 3 )
c. ( frac{3 mu_{0} l i}{2 pi} )
D. ( frac{2 mu_{0} l i}{3 pi} )
12
243 An electron of charge ( e ) and mass ( m ) describes a circular path of radius ( r ) when it is projected with a velocity ( v ) perpendicular to a uniform magnetic field, then its frequency is :
( ^{A} cdot frac{1}{2 pi} sqrt{frac{B e}{m}} )
в. ( frac{1}{2 pi} frac{B e}{m} )
c. ( frac{1}{2 pi} frac{m}{B e} )
D. ( frac{1}{2 pi} frac{m e}{2} )
12
244 between conductors carrying currents
( I_{1} ) and ( I_{2} ) is varied. Which of the
following graphs correctly represents
the variation of force ( (boldsymbol{F}) ) between the
conductors and distance ( (boldsymbol{d}) ) ?
( A )
в.
( c )
D. none of these
12
245 A particle with charge ( q ) having
momentum ( p ) enters a uniform
magnetic field normally. The magnetic filed has magnitude ( B ) and is confined to a region of width ( d, ) where ( d<frac{p}{B q} )
The particle is deflected by an angle ( theta ) in
crossing the field.
( A )
[
sin theta=frac{p d}{B q}
]
B.
[
sin theta=frac{B q}{q d}
]
( c )
[
sin theta=frac{p}{B d q}
]
D.
[
sin theta=frac{B q d}{p}
]
12
246 A straight wire lying in a horizontal plane carries a current from magnetic north to magnetic south. What is the direction of force felt by the wire? 12
247 Deduce an expression for the force on a current carrying conductor placed in a magnetic field. 12
248 An electron moving at right angle to a uniform magnetic field completes a circular orbit in 1 micro – second. Find
the magnetic field.
Ans. ( 3.53 times 10^{-5} T )
12
249 A vertical circular coil of radius ( 0.1 m )
and having 10 turns carries a steady current. When the plane of the coil is normal to the magnetic meridian, a neutral point is observed at the centre
of the coil. If ( boldsymbol{B}_{boldsymbol{H}}=mathbf{0 . 3 1 4} times mathbf{1 0}^{-mathbf{4}} boldsymbol{T} )
the current in the coil is :
( mathbf{A} cdot 0.5 A )
B. 0.25 A
( c cdot 2 A )
D. ( 1 A )
12
250 A square loop, carrying a steady current
Is placed in a horizontal plane near a
long straight conductor carrying a
steady current ( I_{1} ) at a distance d from
the conductor as shown in figure. The loop will experience:
A. a net repulsive force away from the conductor
B. a net torque acting upward perpendicular to the horizontal plane
C. a net torque acting downward normal to the horizontal plane
D. a net attractive force towards the conductor
12
251 The magnetic induction at a point at a large distance d on the axial line of
circular coil of small radius carrying
current is ( 120 mu T . ) At a distance 2 d the
magnetic induction would be:
A. ( 60 mu T )
в. зод ( T )
( c cdot 15 mu T )
D. 240muT
12
252 A moving electron enters a uniform
magnetic field perpendicularly. Inside the magnetic field, the electron travels along:
A. a straight line
B. a parabola
c. a circle
D. a hyperbola
12
253 A toroid is
A. a finite
B. an endless
C . straight
D. either A or B
12
254 The resistance of a galvanometer is 50 ohm and the maximum current which
can be passed through it is ( 0.002 A ) What resistance must be connected to
it in order to convert it into an ammeter
of range ( 0-0.5 A ? )
A. 0.2 onm
B. 0.002 ohm
c. 0.02 ohm
D. 0.5 ohm
12
255 The quarks have fractional electronic charge e/3 and 2e/3. Then why is such a fractional electronic charge not reflected on the oil drops? This question has multiple correct options
A. Quarks cannot be gained or lost
B. Only electrons can be gained or lost
c. To lose quark, energy in MeV is required
D. single quark is unstable
12
256 A charged particle is moving in a uniform magnetic field in a circular
path. The energy of the particle is doubled. If the initial radius of the
circular path was ( R, ) the radius of the new circular path after the energy is doubled will be:
A. ( 0.5 R )
в. ( sqrt{2} R )
( c .2 R )
D. ( frac{R}{sqrt{2}} )
12
257 An elevator carrying a charge of ( 0.5 C ) is
moving down with a velocity of ( 5 times ) ( 10^{3} m s^{-1} . ) The elevator is ( 4 m ) from the
bottom and ( 3 m ) horizontally form ( P ) as
shown in figure. What magnetic field (in
( mu T ) ) does it produce at point ( P ? )
12
258 A straight current carrying conductor is kept along the axis of circular loop carrying current. The force exerted by the straight conductor on the loop is
A. perpendicular to the plane of the loop.
B. in the plane of the loop, away from the center.
C. on the plane of the loop, towards the center.
D. zero.
12
259 If an oscillation copper disc is placed in a
magnetic field, then
A. The frequency of oscillations is decreasing continuously.
B. The frequency of oscillations is increasing continuously.
C. The frequency of oscillations is constant
D. None of these.
12
260 A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in a uniform magnetic field of induction 2 tesla. If the magnetic field is perpendicular to the length of the
wire, the force acting on the wire is:
A. 2.4
B. 1.2 N
c. 3.0 N
D. 2.0 N
12
261 ( boldsymbol{x}=mathbf{0}, boldsymbol{y}=-mathbf{0 . 5 0 0 m}, boldsymbol{z}=mathbf{0} ) 12
262 A 200 turn closely wound circular coil of
radius ( 15 mathrm{cm} ) carries a current of ( 4 mathrm{A} )
The magnetic moment of this coil is:
( mathbf{A} cdot 36.5 A m^{2} )
B . ( 56.5 A m^{2} )
( mathbf{c} cdot 66.5 A m^{2} )
D. ( 108 A m^{2} )
12
263 A hollow tube is carrying an electric current along its length distributed
uniformly over its surface. The magnetic field :
This question has multiple correct options
A. increases linearly from the axis to the surface
B. is constant inside the tube
c. is zero at the axis
D. is zero just outside the tube
12
264 If a toroid uses bismuth for its core, the
field in the core compared to that in empty core will be slightly
A. greater
B. smaller
c. equal
D. None of these
12
265 Find the ratio of the conduction
electrons to the total number of atoms
in the given conductor.
A. Almost 1: 4
B. Almost 1: 2
c. Almost 2: 1
D. Almost 1: 1
12
266 A slightly divergent beam of charged particles accelerated by a Potential difference B propagates from a point ( mathbf{A} ) along the axis of solenoid. The beam is brought into focus at a distance I from the point ( A ) at two successive values of
magnetic induction ( B_{1} ) and ( B_{2} ). If the
specific charge ( mathrm{q} / mathrm{m} ) of the particles is ( frac{boldsymbol{q}}{boldsymbol{m}}=frac{boldsymbol{x} boldsymbol{pi}^{2} boldsymbol{V}}{boldsymbol{l}^{2}left(boldsymbol{B}_{2}-boldsymbol{B}_{1}right)^{2}} cdot ) Find ( boldsymbol{x} )
12
267 A charged particle moves in a gravity
free space where an electric field of
strength ( mathrm{E} ) and a magnetic field of induction B exist. Which of the following
statement is/are correct?
This question has multiple correct options
A. If ( E neq 0 ) and ( B neq 0, ) velocity of the particle may remain constant
B. if ( E=0 ), the particle cannot trace a circular path
c. if ( E=0 ), kinetic energy of the particle remains constant
D. none of these
12
268 The electrons in the beam of a television
tube move horizontally from south to north. The vertical component of the
earths magnetic field points down. The electron is deflected towards
A . east
B. no deflection
c. west
D. north to south
12
269 A conducting loop carrying a current ( boldsymbol{I} ) is placed in a uniform magnetic field pointing into the plane of the paper as
shown. The loop will have a tendency to:
A. contract
B. expand
c. move towards +ve x-axis
D. move towards ve x axis
12
270 Dimensions of Gyromagnetic ratio are?
A ( cdotleft[L^{1} M^{0} T^{1} I^{1}right] )
B . ( left[L^{0} M^{-1} T^{1} Iright] )
C ( cdotleft[L^{1} M^{0} T^{0} I^{-1}right] )
D cdot ( left[L^{-1} M^{0} T^{1} I^{1}right] )
12
271 A 2 MeV proton is moving perpendicular to a uniform magnetic field of 2.5 tesla. The force on the proton is
В. ( 7.6 times 10^{-11} N )
c. ( 2.5 times 10^{-11} N )
D. ( 7.6 times 10^{-12} N )
12
272 An electron and a proton are projected with same velocity perpendicular to a
magnetic field.Which particle will describe the smaller circle?
12
273 A solenoid of ( 1.5 mathrm{m} ) length and ( 4.0 mathrm{cm} ) diameter possesses 100 turns per meter. A current of 5 amperes is flowing through it. The magnetic induction at axis inside the solenoid is:
A ( cdot 2 pi times 10^{-4} mathrm{T} )
В . ( 2 pi times 10^{-5} ) Т
c. ( 2 pi times 10^{-2} ) gauss
D. ( 2 pi times 10^{-5} ) gauss
12
274 An electron beam is moving between two parallel plates having electric field
( 1.125 times 10^{-6} N / m . ) A magnetic field
( 3 times 10^{-10} T ) is also applied, so that
beam of electrons do not deflect. The
velocity of the electron is
( A cdot 4225 mathrm{m} / mathrm{s} )
B. 3750 m/s
c. ( 2750 mathrm{m} / mathrm{s} )
D. 3200 ( mathrm{m} / mathrm{s} )
12
275 A neutral particle is at rest in a uniform magnetic field ( bar{B} ). At ( t=0 ), particle decays into two particles each of mass
( m^{prime} ) and one of them having charge ( ^{prime} q^{prime} )
Both of these move off in separate paths lying in plane perpendicular to ( bar{B} ). At later time, the particles collide. If this time of collision is ( x pi m / q B ) then ( x ) is (neglecting the interaction force).
12
276 A small current element of length ( d l ) and carrying current is placed at (1,1,0) and is carrying current in ‘ ( +z^{prime} ) direction. If magnetic field at origin be ( vec{B}_{1} ) and at point (2,2,0) be ( vec{B}_{2} ) then
A ( cdot vec{B}=vec{B} )
B . ( left|vec{B}_{1}right|=left|2 vec{B}_{2}right| )
c. ( vec{B}_{1}=-vec{B}_{2} )
D . ( vec{B}_{1}=-2 vec{B}_{2} )
12
277 The sensitivity of a voltmeter of 1000 ohms is ( 1 mathrm{mV} / ) div When a resistance of
( 99,000 Omega ) is connected in series, its sensitivity becomes:
A. 1 Volt / div
B. 10 Volt / div
c. 1.1 volt / div
D. 0.1 volt / div
12
278 The relation between voltage sensitivity
( left(sigma_{v}right) ) and current sensitivity ( left(sigma_{i}right) ) of ( a ) moving coil galvanometer is (resistance of galvanometer is ( G ) ).
A ( cdot frac{sigma_{i}}{G}=sigma_{v} )
в. ( frac{sigma_{v}}{G}=sigma )
c. ( frac{G}{sigma_{v}}=sigma )
D. None of the above
12
279 Two wires carry currents of ( 100 A ) and
( 200 A ) respectively and they repel each other with a force of ( 0.4 N / m . ) The distance between them will be
A . ( 1 m )
B. ( 1 mathrm{cm} )
( c .50 mathrm{cm} )
D. ( 25 mathrm{cm} )
12
280 A metal ring kept (supported by a card
board) on the top of a fixed solenoid
carry a current I as shown in figure. The centre of the ring coincides with the axis of the solenoid. If the current in the
solenoid is switched off, then
A. magnetic flux linked with the metal ring increases.
B. current induced in the metal ring in clockwise direction
c. metal ring will not remain on the cardboard
D. both
(a) and
(b) are correct
12
281 A current of ( 10 A ) passes through two
very long wires held parallel to each other and separated by a distance of
1 ( m ). What is the force per unit length
between them?
12
282 Two circular coils ( X ) and ( Y )
having radii ( mathrm{R} ) and ( mathrm{R} / 2 ) respectively are placed in horizontal plane with their centres coinciding with each other. Coil X has current I flowing through it in the clockwise sense. What must be the
current in the coil ( Y ) to make the total
magnetic field at the centre of two coils zero?
12
283 An ammeter has a resistance of ( G )
ohms and range of ( I ) amperes. The value of resistance required in parallel to
convert it into an ammeter of range ( boldsymbol{n} boldsymbol{I} )
is
A ( . n G )
в. ( (n-1) G )
c. ( G /(n-1) )
D. ( G / n )
12
284 Equal currents are passing through two very long and straight parallel wires in the same direction. They will
A. repel each other
B. attract each other
c. lean towards each other
D. neither attract nor repel each other
12
285 There will be no force between two
current carrying wires if currents are
A. Parallel to each other
B. Antiparallel to each other
C. Perpendicular to each other
D. Nothing can be said
12
286 A particle initially moving towards south in a vertically downward magnetic field is deflected toward the
east. What is the sign of the charge on
the particle?
12
287 A proton and an alpha particle enter into a uniform magnetic field with the same velocity.The period of rotation of the alpha particle will be
A. four times that of proton
B. two times that of proton
c. three times that of proton
D. same as that of proton
12
288 The direction of force on a current
carrying conductor placed in a magnetic field can be reversed by
reversing the direction of current flowing in the conductor. True/False?
12
289 Charge ( q ) is uniformly spread on a thin
ring of radius ( R ). The ring rotates about its axis with a uniform frequency ( boldsymbol{f} boldsymbol{H} boldsymbol{z} ) The magnitude of magnetic induction at the centre of the ring is
A ( cdot frac{mu_{0} q f}{2 R} )
в. ( frac{mu_{0} q}{2 f R} )
c. ( frac{mu_{0} q}{2 pi f R} )
D. ( frac{mu_{0} q f}{2 pi R} )
12
290 The S.I. unit of magnetic field intensity
is :
A. webber
B. Tesla
c. owersted
D. Gauss
12
291 A toroid of n turns, mean radius R and
cross-sectional radius a carries current
I. It is placed on a horizontal table taken as ( x-y ) plane. Its magnetic moment
( bar{M} ) is
A. is non-zero and points in the z-direction by symmetry
B. points along the axis of the toroid ( (bar{M}=M phi) )
c. is zero, otherwise there would be field falling as ( frac{1}{r^{3}} ) at large distances outside the toroid
D. is pointing radially outwards
12
292 A circular loop carrying a current ( I ) is
placed in the ( x ) -y plane as shown in figure.An uniform magnetic field ( vec{B} ) is oriented along the positive z-axis.The
loop tends to:
A. expand
B. contract
( c . ) rotate about x-axis
D. rotate about y-axis
12
293 When radiation emitted by a
radioactive substance is subjected to a magnetic field, alpha-particles describe a circle in the clockwise direction
A. beta and gamma particles will also be deflected in the same direction
B. gamma rays will be deflected to describe a circle in the counter clockwise direction but beta particles will not be deflected
C . gamma rays will not be deflected and beta rays will move in a circular path in the counter clockwise sense
D. beta and gamma rays will describe a circle in the counter clockwise sense
12
294 Two long parallel wires are at a distance
of ( 1 mathrm{m} ). If both of them carry one ampere of current in same direction, then the
force of attraction on unit length of the wires will be
A ( cdot 2 times 10^{-7} N / m )
B . ( 4 times 10^{-7} N / m )
c. ( 8 times 10^{-7} N / m )
D. ( 10^{-7} N / m )
12
295 Write the following steps of an experiment in a sequential order to show that a current carrying conductor sets up a magnetic field around it.
(a) Pass the insulted copper wire through the small hole at the centre of the carboard and perpendicular to it.
(b) Paste a white paper on a rectangular cardboard and make a small hole at its
centre.
(c) Connect this wire to a battery, a
switch and a variable resistor in series.
(d) Clamp this cardboard to a stand in a horizontal position and sprinkle some iron filings over it.
(e) Now, when the circuit is closed, the iron filings on the carboard form concentric circles around the wire.
A. bdace
B. baced
c. adbec
( mathbf{D} cdot e d a b c )
12
296 Two wires carrying equal current ( I ) are a
distance ( a ) apart.
If the current through wire one is doubled while the current through the wire two is tripled, what is the ratio of the force that wire two exerts on wire 1
( F_{1} ) ) to the force that wire one exerts on
wire ( 2left(F_{2}right) ? )
A . 4: 09
B. 2:03
( c cdot 1: 0 )
D. 3:02
E. 9: 04
12
297 What is the speed at the top?
A ( frac{E}{B} )
в. ( frac{E}{2 text { }} )
c. ( frac{2 E}{B} )
D. ( frac{B}{2 E} )
12
298 toppr
Q Type your question.
cnargea partıcies. wıth a rıela b resia,
is found that the filter transmits ( alpha ) –
particles each of energy ( 5.3 mathrm{MeV} ). The magnetic field is increased to ( 2.3 mathrm{B} )
Tesla and deuterons are passed into the filter. The energy of each deuteron
transmitted by the filter is MeV.
A . 28 Mev
B. 14Mev
c. 7 Mev
D. 18Me
12
299 f the magnetic induction at the center of the rotating sphere is ( vec{B}= ) ( frac{2}{X} mu_{0} omega sigma R(hat{k})left[quad sin ^{3} theta=frac{1}{4}(3 sin thetaright. )
Find ( X ? )
12
300 The force of repulsion between two parallel wires is ( f ) when each one of
them carries a certain current ( I ). If the
current in each is doubled, the force between them would be
A ( cdot frac{4}{f} )
B. ( 4 f )
c. ( 2 f )
D. ( f )
12
301 A particle with charge ( q ) is projected successively along the ( x ) and ( y ) axes with same speed v. The force on the particle in these situations are ( boldsymbol{q} boldsymbol{v} boldsymbol{B}(-boldsymbol{3} hat{boldsymbol{j}}+boldsymbol{4} hat{boldsymbol{k}}) )
and ( q v B(3 hat{i}) ) respectively. Find the unit vector in direction of ( vec{B} )
12
302 A moving coil galvanometer A has 100
turns and resistance ( 10 Omega ). Another
galvanometer B has 50 turns and resistance 5Omega. The other quantities are same in both the cases. Then the
voltage sensitivity of
A. A is greater than that of
B. B is greater than that of
c. A and B is Same
D. cannot be compared
12
303 The minimum magnetic dipole moment of electron in hydrogen atom is
A ( cdot frac{e h}{2 pi m} )
в. ( frac{e h}{4 pi m} )
c. ( frac{e h}{pi m} )
( D )
12
304 A current of ( 4 A ) flows through 5 turn coil
of a tangent galvanometer having a diameter of ( 30 mathrm{cm} . ) If the horizontal
component of Earth’s magnetic induction is ( 4 times 10^{-5} T ), find the
deflection produced in the coil. ( left[text { Given } mu_{0}=4 pi times 10^{-7} H m^{-1}right] )
12
305 A device used for measuring small
currents due to changing magnetic field is known as:
A. galvanometer
B. ammeter
c. potentiometer
D. voltmeter
12
306 A wire ( 28 mathrm{m} ) long is bent into ( mathrm{N} ) turns of circular coil of diameter ( 14 mathrm{cm} ) forming a solenoid of length ( 60 mathrm{cm} ). Calculate the magnetic field inside it when a current of 5 amp passed through it. ( left(mu_{0}=12.57 times 10^{-7} m^{-1}right) )
A ( cdot 6.67 times 10^{-1} T )
( T )
в. ( 6.67 times 10^{-4} T )
c. ( 6.67 times 10^{4} T )
D. ( 2.67 times 10^{-4} T )
12
307 Ine magnetıc tıeld ( boldsymbol{B} ) at the centre of a
circular coil of radius ( r ) is ( pi ) times that
due to a long straight wire at a distance
( r ) from it, for equal currents. The
following diagram shows three cases. In
all cases the circular part has radius ( r )
and straight ones are infinitely long. For
the same current the field ( B ) at centre ( P )
in cases 1,2,3 has the ratio:
( ^{mathbf{A}} cdotleft(-frac{pi}{2}right):left(frac{pi}{2}right):left(frac{3 pi}{4}-frac{1}{2}right) )
B ( cdotleft(-frac{pi}{2}+1right):left(frac{pi}{2}+1right):left(frac{3 pi}{4}+frac{1}{2}right) )
( left(-frac{pi}{2}right):left(frac{pi}{2}right):left(frac{3 pi}{4}right) )
D ( cdotleft(-frac{pi}{2}-1right):left(frac{pi}{2}-frac{1}{4}right):left(frac{3 pi}{4}+frac{1}{2}right) )
12
308 The magnetic moment associated with
a circular coil of 35 turns and radius 25
( mathrm{cm}, ) if it carries a current of ( 11 mathrm{A} ) is:
A ( .72 .2 A m^{2} )
B . ( 70.5 A m^{2} )
c. ( 74.56 A m 2 )
D. ( 75.56 A m^{2} )
12
309 A wire is wound on a long rod of
material of relative permeability ( mu_{r}= )
4000 to make a solenoid. If the current
through the wire is ( 5 A ) and number of
turns per length is 1000 per meter, then the magnetic field inside the solenoid is:
A. ( 25.12 mathrm{mT} )
B. ( 12.56 mathrm{mT} )
c. ( 12.56 T )
D. 25.12 T
12
310 A neutron, a proton, an electron and an
( alpha ) particle enter perpendicular
uniform magnetic field, with the same uniform velocity. The path of electron in the following figure will be:
( A cdot 4 )
B. 3
( c cdot 2 )
D.
12
311 projected with a velocity ( v_{0} ) towards a
circular region having a uniform
magnetic field ( B ) perpendicular and
into the plane of paper from point ( boldsymbol{P} ) as
shown in the figure. ( boldsymbol{R} ) is the radius and
O is the center of the circular region. If
the line ( O P ) makes an angle ( theta ) with the
direction of ( v_{0} ) then the value of ( v_{0} ) so
that particle passes through ( boldsymbol{O} ) is
A ( cdot frac{q B R}{m sin theta} )
B. ( frac{q B R}{2 m sin theta} )
c. ( frac{2 q B R}{m sin theta} )
D. ( frac{3 q B R}{2 m sin theta} )
12
312 The magnetic field inside a solenoid carrying current.
A. is the same at all points
B. is zero at all points
c. becomes zero at its north pole
D. becomes zero at its south pole
12
313 An observer ( A ) and a charge ( Q ) are fixed
in a stationary frame ( F_{1} ). an observer ( mathrm{B} )
is fixed in a frame ( F_{2}, ) which is moving
with respect to ( boldsymbol{F}_{1}: )
This question has multiple correct options
A. both A and B will observe electric fields
B. both A and B will observe magnetic fields
C. neither A nor B will observe magnetic fields
D. B will observe a magnetic field, but A will not
12
314 On passing electric current in two long straight conductors in mutually opposite directions, the magnetic force acting between them will be
A. attractive
B. repulsive
c. both attractive and repulsive
D. neither attractive nor repulsive
12
315 An electron, moving along the ( x ) -axis with an initial energy of ( 100 e V ), enters a region of magnetic field ( vec{B}=(1.5 times )
( left.10^{-3} Tright) hat{k} ) at ( S(text { See figure }) . ) The field
extends between ( x=0 ) and ( x=2 c m )
The electron is detected at the point ( Q ) on a screen placed ( 8 mathrm{cm} ) away from the point S. The distance d between P and Q
(on the screen) is :
(electron’s charge ( =1.6 times 10^{-19} mathrm{C}, ) mass
of electron ( left.=9.1 times 10^{-31} k gright) )
A ( .12 .87 mathrm{cm} )
В. ( 1.22 mathrm{cm} )
c. ( 11.65 mathrm{cm} )
D. ( 2.25 mathrm{cm} )
12
316 Consider points ( A, B, C, D ) on a horizontal cardboard equidistant from center ( boldsymbol{O} ) as shown in the figure. ( mathbf{A} ) copper wire perpendicular to the
cardboard passes through the center ( O ) and carries an electric current
flowing upwards. Deflection of magnetic needle will be maximum when it is kept
at the point
A . ( A )
в. ( B )
( c . c )
( D )
12
317 A solenoid having an iron core has its
terminals connected across an ideal DC
source and it is in steady state. If the
iron core is removed, the current flowing
through the solenoid just after removal
of rod.
A . increases
B. decreases
c. remains unchanged
D. nothing can be said
12
318 A charge ( boldsymbol{q}(>mathbf{0}) ) moves towards the
centre of a circular loop of radius ( boldsymbol{R} )
along its axis. The magnitude of B along
the periphery of the loop is
A . zero
B. ( frac{mu_{0}}{4 pi} frac{q v R}{sqrt{left(R^{2}+x^{2}right)^{3}}} )
c. ( frac{q v R}{sqrt{R^{2}+x^{2}}} )
D. ( frac{mu_{0}}{4 pi} frac{q v R}{sqrt{R^{2}+x^{2}}} )
12
319 The number of electrons to be put on a
spherical conductor of radius ( 0.1 m ) to
produce an electric field of ( 0.036 N / C )
just above its surface is
A ( cdot 2.7 times 10^{5} )
В. ( 2.6 times 10^{5} )
c. ( 2.5 times 10^{5} )
D. ( 2.4 times 10^{5} )
12
320 When a charged particle is projected
perpendicular to a magnetic field:
A. Its path is circular in a plane perpendicular to the plane of magnetic field
B. The speed and kinetic energy of the particle remains constant
C. The velocity and momentum of the particle changes only in direction
D. The time period of revolution, angular and frequency of revolution is independent of velocity of the particle and radius of circular path
12
321 A current carrying conductor
experiences a force when placed in a
magnetic field. Type 1 for true and 0 for false
12
322 A moving coil ammeter requires a potential difference of ( 0.4 V ) across it for
full scale deflection. It has fixed shunt
resistance of 0.01 ohm with a coil
circuit resistance of ( boldsymbol{R}=mathbf{1} boldsymbol{k} ) ohm. The
value of shunt required to give full scale deflection when the total current is ( 10 A )
is equal to
A. 0.02 ohm
B. 0.04 ohm
c. 0.05 ohm
D. 0.06 ohm
12
323 In the given figure, what is the magnetic field induction at point 0
A ( cdot frac{mu_{0} l}{4 pi r} )
в. ( frac{mu_{0} l}{4 r}+frac{mu_{0} l}{2 pi r} )
c. ( frac{mu_{o} l}{4 r}+frac{mu_{0} l}{4 pi r} )
D. ( frac{mu_{0} l}{4 r}-frac{mu_{0} l}{4 pi r} )
12
324 Which of the following particle would follow the path as shown in the above
figure?
A. Proton
B. Electron
C . Neutron
D. x-ray
E. Photon of red ligth
12
325 A current i is flowing in a conductor as
shown in the figure. The magnetic
induction at point 0 will be :
A . zero
B. ( mu_{0} i / r )
( c cdot 2 mu_{0} i / r )
( mathbf{D} cdot mu_{0} i / 4 r )
12
326 A non-relativistic proton beam passes without deviation through a region of space where there are uniform
transverse mutually perpendicular electric and magnetic fields with ( boldsymbol{E}= )
( 120 k V m^{-1} ) and ( B=50 m T . ) Then the
beam strikes a grounded target. Find the force imparted by the beam on the target if the beam current is equal to
( boldsymbol{i}=mathbf{0 . 8} boldsymbol{m} boldsymbol{A} )
Mass of protons ( =1.67 times 10^{-27} k g )
12
327 Assertion
A current carrying conductor experiences a force in a magnetic field.
Reason
The net charge on a current carrying
conductor is zero.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
328 Pitch of the helical path described by the particle is :
A. ( frac{2 pi m v_{0}}{B_{0} q} )
В. ( frac{sqrt{3} pi m v_{0}}{2 B_{0} q} )
c. ( frac{pi m v_{0}}{B_{0} q} )
D. ( frac{2 sqrt{3} pi m v_{0}}{B_{0} q} )
12
329 A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively, this region of space may not have
A. ( E=0, B=0 )
B. ( E=0, B neq 0 )
c. ( E neq 0, B=0 )
D. ( E neq 0, B neq 0 )
12
330 If the work done in turning a magnet of
magnetic moment ( M ) by an angle of ( 90^{circ} ) from the magnetic meridian is n times the corresponding work done to turn it
through an angle of ( 60^{circ} ), then the value
of ( n ) is
A . 1
B. 2
( c cdot frac{1}{2} )
D.
12
331 A long horizontally fixed wire carries a
current of 100 ampere. Directly above and parallel to it is a fine wire that
carries a current of 20 ampere and
weights 0.04 newton per meter. The distance between the two wires for
which the upper wire is just supported by magnetic repulsion is:
( mathbf{A} cdot 10^{-2} m m )
B. ( 10^{-2} mathrm{cm} )
( mathrm{c} cdot 10^{-2} mathrm{m} )
D. ( 10^{-2} k m )
12
332 A particle of charge ( q ) and mass ( m ) moves in a circular orbit of radius r with
angular speed ( omega . ) The ratio of the
magnitude of its magnetic moment to that of its angular momentum depends
on
A. ( omega ) and ( q )
B. ( omega, q ) and ( m )
c. ( q ) and ( m )
D. ( omega ) and ( m )
12
333 State two ways by which the magnetic field of a solenoid can be made stronger 12
334 Assertion: Diamagnetism is universal, it is present in all materials.

Reason: Field due to induced magnetic
moment is opposite to the magnetising
field
A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true and reason is not the correct explanation of assertion
c. If assertion is true but reason is false.
D. If both assertion and reason are false

12
335 A square loop ( A B C D, ) carrying a
current ( boldsymbol{I}_{1}, ) is placed near and coplanar
with a long straight conductor ( boldsymbol{X} boldsymbol{Y} )
carrying a current ( I_{1} ), as shown in
figure. The net force on the loop will be
A ( cdot frac{mu_{0} I_{1} I_{2}}{2 pi} )
B. ( frac{mu_{0} I_{1} I_{2} L}{2 pi} )
c. ( frac{2 mu_{0} I_{1} I_{2} L}{2 pi} )
D. ( frac{2 mu_{0} I_{1} I_{2}}{3 pi} )
12
336 The coercivity of a small magnet where the ferromagnet gets demagnetised is
( 3 times 10^{3} A m^{-1} . ) The current required to
be passed in a solenoid of length ( 10 mathrm{cm} )
and number of turns ( 100, ) so that the magnet gets demagnetised when inside the solenoid, is:
A . ( 6 A )
в. 30 тА
( c .60 m A )
D. ( 3 A )
12
337 Find the magnetic field intensity due to
a thin wire carrying current ( I ) in the
figure :
A ( cdot frac{mu_{0} i}{2 pi R}(pi-a+tan a) )
в. ( frac{mu_{0} i}{2 pi R}(pi-a) )
c. ( frac{mu_{0} i}{2 pi R}(pi+a) )
D. ( frac{mu_{0}}{2 pi R}(pi+a-text { tana }) )
12
338 The magnetic force per unit length on a wire carrying a current of ( 10 mathrm{A} ) and
making an angle of ( 45^{0} ) with the direction of a uniform magnetic field of ( 0.20 mathrm{T} ) is
A ( cdot 2 sqrt{2} N m^{-1} )
B. ( frac{2}{sqrt{2}} N m^{-1} )
( ^{c} cdot frac{sqrt{2}}{2} N m^{-1} )
D. ( 4 sqrt{2} N m^{-1} )
12
339 Find the magnetic induction ( B ) on the axis as a function of ( x )
A ( cdot B=frac{1}{2} mu_{0} n Ileft(1-frac{x}{sqrt{x^{2}+R^{2}}}right) )
в. ( quad B=frac{1}{2} mu_{0} n Ileft(2-frac{x}{sqrt{x^{2}+R^{2}}}right) )
c. ( _{B}=frac{1}{2} mu_{0} n Ileft(R-frac{x}{sqrt{x^{2}+R^{2}}}right) )
D. ( B=frac{1}{2} mu_{0} n Ileft(X-frac{x}{sqrt{x^{2}+R^{2}}}right) )
12
340 Which is the magnitude of force on a
current I carrying conductor of length ( l ) placed in a magnetic field B ?
A ( . B I l^{2} )
в. Вl/
c. ( B l I )
D. ( B I^{2} )
12
341 A device used for detecting small currents due to changing magnetic field is known as:
A. Galvanometer
B. Ammeter
c. Voltmeter
D. Potentiometer
12
342 An electron enters a chamber in which a
uniform magnetic field is present as
shown. Ignore gravity. During its motion inside the chamber
field
A. The force on the electron remains constant
B. The kinetic energy of the electron remains constantt
c. The momentum of the electron remains constant
D. The speed of the electron increases at a uniform rate
12
343 An electric field of ( 1500 V / m ) and ( a )
magnetic field of ( 0.04 W b / m^{2} ) act on a moving electron. The minimum uniform speed along a straight line the electron could have is.
A ( cdot 1.6 times 10^{15} mathrm{m} / mathrm{s} )
в. ( 6 times 10^{-16} mathrm{m} / mathrm{s} )
C ( .3 .75 times 10^{4} mathrm{m} / mathrm{s} )
D. ( 3.75 times 10^{2} mathrm{m} / mathrm{s} )
12
344 A long solenoid has magnetic field strength of ( 3.14 times 10^{-2} mathrm{T} ) inside it
when a current of ( 5 A ) passes through it The number of turns in 1 m of the
solenoid is
A. 1000
B. 3000
c. 5000
D. 10000
12
345 A magnetic dipole in a constant
magnetic field has
A. Minimum potential energy when the torque is maximum.
B. Zero potential energy when the torque is minimum.
C. Zero potential energy when the torque is maximum.
D. Maximum potential energy when the torque is maximum.
12
346 A circular coil expands radially in a
region of magnetic field and no electromotive force is produced in the coil. This is because
A. the magnetic field is constant
B. the magnetic field is in the same plane as the circular coil and it may or may not vary
c. the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is decreasing suitably
( D . ) both ( (b) ) and ( (c) )
12
347 If a charged particle goes unaccelerated in a region containing electric and magnetic fields, then This question has multiple correct options
A. ( vec{E} ) must be perpendicular to ( vec{B} )
B . ( vec{v} ) must be perpendicular to ( vec{E} )
C. ( vec{v} ) must be perpendicular to ( vec{B} )
D. E must be equal to vB
12
348 An ideal solenoid of cross-sectional
( operatorname{area} 10^{-4} m^{2} ) has 500 turns per metre.
At the centre of this solenoid, another
coil of 100 turns is wrapped closely around it, if the current in the coil
charges from 0 to ( 2 A ) in 3.14 ms, the
emf developed in the second coil is:
( mathbf{A} cdot 1 m V )
B. ( 2 m V )
( mathbf{c} .3 m V )
D. ( 4 mathrm{mV} )
12
349 A particle of charge q is moving with
velocity v in the presence of crossed
electric field E and magnetic field B as shown. Write the condition under which
the particle will continue moving along x-axis. How would the trajectory of the
particle be affected if the electric field is suddenly switched off?
12
350 A proton moving with a constant speed passes through a region of space without any change in its speed. If ( boldsymbol{E} )
and ( B ) represent the electric and magnetic fields respectively, this region of space may have
a) ( boldsymbol{B} neq mathbf{0}, boldsymbol{E}=mathbf{0} )
b) ( boldsymbol{B}=mathbf{0}, boldsymbol{E} neq mathbf{0} )
c) ( B=0, E=0 )
d) ( boldsymbol{B} neq mathbf{0}, boldsymbol{E} neq mathbf{0} )
( A cdot a, b, c ) are true
B. b, c, dare true
( c cdot a, b, d ) are true
D. a, c, d are true
12
351 topp
( Q ) Type your question
as ‘positive’ when the wires repel each ther and ‘negative’ when the wires attract each other, the graph showing
the dependence of ‘F’, on the product
( I_{1} I_{2}, ) would be
( c )
( D )
12
352 The force exerted on a current-carrying wire placed in a magnetic field is zero when the angle between the wire and the direction of magnetic field is.
A ( .180^{circ} )
B. ( 90^{circ} )
( c cdot 60^{circ} )
D. ( 15^{circ} )
12
353 Give the principle of moving coil galvanometer? What is the advantage of radial magnetic field in the galvanometer? 12
354 A galvanometer of resistance ( 50 Omega ) is
connected to a battery of ( 8 V ) along with a resistance of ( 3950 Omega ) in series. A full
scale deflection of 30 div is obtained in
the galvanometer. In division, the resistance in series should be
A. 1950
в. 7900
c. 2000
D. 7950
12
355 The rigid conducting thin wire frame carries an electric current ( I ) and this
frame is inside a uniform magnetic field ( vec{B} ) as shown in fig. Then
A. the net magnetic force on the frame is zero but the torque is not zero
B. the net magnetic force on the frame and the torque due to magnetic field are both zero
c. the net magnetic force on the frame is not zero and the torque is also not zero
D. none of these
12
356 A uniform conducting wire ( A B C ) lying in ( X Y ) plane has a mass of ( 10 g . A )
current of ( 2 A ) flows through it. The wire
is kept in a uniform magnetic field ( B=2 T ) which acceleration of the wire
is
A. Zero
B ( cdot 12 m / s^{2} ) and along postive ( Y ) -axis
C. ( 12 times 10^{-3} mathrm{m} / mathrm{s}^{2} ) along postive ( Y ) -axis
D. ( 12 m / s^{2} ) and along postive ( X ) -axis
12
357 The magnetic field at the centre of
circular loop in the circuit carrying
current ( I ) shown in the figure is :
A ( cdot frac{mu_{0}}{4 pi} frac{2 I}{r}(1+pi) )
в. ( frac{mu_{0}}{4 pi} frac{2 I}{r}(pi-1) )
c. ( frac{mu_{0}}{4 pi} frac{2 I}{r} )
D. ( frac{mu_{0}}{4 pi} frac{I}{r}(pi+1 )
12
358 An electron is shot in a steady electric and magnetic field such that its velocity is ( V ). Electric field ( E ) and
magnetic field ( boldsymbol{B} ) are
mutually perpendicular. The magnitude
of ( boldsymbol{E} ) is 1 volt ( / mathrm{cm} ) and that of ( boldsymbol{B} ) is
2 tesla. Now it happens that the Lorentz (Magnetic) force cancels with the
electrostatic force on the electron, then
the velocity of the electron is:
A. ( 50 mathrm{ms}^{-1} )
B. ( 2 mathrm{cms}^{-1} )
c. ( 0.5 mathrm{cms}^{-1} )
D. ( 200 m s^{-1} )
12
359 What is a solenoid? Draw a sketch to
show the magnetic field pattern produced by a current carrying solenoid
12
360 Two circular coils ( P ) and ( Q ) are made
from similar wire but radius of ( Q ) is
twice that of ( P ). Relation between the
values of potential difference across them so that the magnetic induction at their centers may be the
same is :
( mathbf{A} cdot V_{Q}=2 V_{P} )
B. ( V_{Q}=3 V_{P} )
( mathbf{c} cdot V_{Q}=4 V_{P} )
D. ( v_{Q}=frac{1}{4} V_{P} )
12
361 Two long parallel wires are a distance 2 a apart, as shown. Point P is in the plane of the wires and a distance a from wire
X. When there is a current lin wire ( X )
and no current in wire ( Y ), the magnitude
of the magnetic field at ( P ) is ( B_{0} . ) When
there are equal currents lin the same direction in both wires, the magnitude of the magnetic field at P is?
A. ( frac{2 B_{0}}{3} )
в. ( B_{0} )
c. ( frac{10 B_{0}}{9} )
D. ( frac{4 B}{3} )
12
362 Best method to increase the sensitivity of the moving coil galvanometer is to decrease
A. radius of the coil
B. number of turns of the coil
c. external magnetic field
D. couple per unit twist
12
363 The figure shows the cross-section of
two long coaxial tubes carrying equal
currents ( I ) in opposite directions. If ( B_{1} )
and ( B_{2} ) are magnetic fields at point
and ( 2, ) as shown in figure then
( mathbf{A} cdot B_{1} neq 0 ; B_{2}=0 )
B . ( B_{1}=0 ; B_{2}=0 )
c. ( B_{1} neq 0 ; B_{2} neq 0 )
D. ( B_{1}=0 ; B_{2} neq 0 )
12
364 toppr
Q Type your question
the conductor, is correctly represented
by the figure:
( A )
B.
( c )
( D )
12
365 A long solenoid has magnetic field strength of ( 3.14 times 10^{-2} mathrm{T} ) inside it
when a current of ( 5 A ) passes through
¡t. The number of turns in 1 m length of the solenoid is
A. 1000
в. 3000
( c .5000 )
D. 10000
12
366 Two particles of different masses ( m_{1} )
and ( m_{2}, ) different charges ( Q_{1} ) and ( Q_{2} )
are accelerated through the same potential difference and then enter a
uniform magnetic field in a direction perpendicular to the field. If they trace circular paths of same radius, then the
ratio of their masses ( left(m_{1} / m_{2}right) ) must be
A ( cdot Q_{2} / Q_{1} )
в. ( Q_{1} / Q_{2} )
c. ( left(Q_{1} / Q_{2}right)^{1 / 2} )
the
D. ( left(Q_{2} / Q_{1}right)^{1 / 2} )
12
367 The deflection in galvanometer falls to ( left[frac{1}{4}right]^{t h} ) when it is shunted by ( 3 Omega ). If additional shunt of ( 2 Omega ) is connected to earlier shunt, the deflection in galvanometer falls to
A ( cdot frac{1}{2} )
B. ( frac{1^{r d}}{3} )
c. ( frac{1}{4}^{t h} )
D. ( frac{1}{8.5} )
12
368 A proton of charge ( e ) moving at speed ( v_{0} ) is placed midway between two parallel wires ( a ) distance a apart, each carrying
current ( I ) in the same direction.
The force on the proton is:
A . 0
в. ( quad e v_{0} frac{I_{0}}{2 pi a} )
( ^{mathrm{c}} cdot operatorname{ev}_{0} frac{I_{0}}{2 pi(2 a)} )
D. ( _{e v_{0}} frac{I_{0}}{2 pi frac{a}{2}} )
E. Unable to be determined
12
369 An electron enters with a velocity ( v ) to
the right in a magnetic field ( B ), also to the right. What direction is the force ( boldsymbol{F} )
on the electron?
A. An upward force
B. A downward force
c. A force to the left
D. No force if felt
12
370 A charged particle moving at right angles to a uniform magnetic field:
A. Gains energy
B. Loses energy
c. Neither gains nor loses energy
D. Either gains or loses energy
12
371 A current-carrying ring is placed in a magnetic field. The direction of the field is perpendicular to the plane of the ring This question has multiple correct options
A. there is no net force on the ring
B. the ring will tend to expand
c. the ring will tend to contract
D. either
(b) or
(c) depending on the directions of the current in the ring and the magnetic field
12
372 Deflection in the galvanometer is
A. Towards right
B. Left
c. No defection
D. None of these
12
373 A bar magnet of magnetic moment ( 2 A m^{2} ) is free to rotate about a vertical axis passing through its center. The magnet is released from rest from east
west position. Then the KE of the magnet as it takes N-S position is
( left(B_{H}=25 mu Tright) )
A. ( 25 mu J )
в. ( 50 mu J )
c. ( 100 mu J )
D. ( 12.5 mu J )
12
374 Write the correct option by observing
the figures.
A. Magnetic field in ( A ) stronger.
B. Magnetic field in ( B ) stronger.
C. Magnetic field in ( A ) and ( B ) are same
D. Magnetic field in ( A ) and ( B ) are weaker.
12
375 A bar magnet of magnetic moment 3.0
( A-m^{2} ) is free to rotate about a vertical
axis passing through its centre. The magnet is released from rest from east west position. Then the kinetic energy of the magnet as it takes North- South position is :
(horizontal component of earths magnetic field is ( 25 mu mathrm{T}) )
B. 75 ( mu ) J
c. ( 100 mu ) J
D. 12.5 ( mu ) )
12
376 The coils made of the same material in
two moving coil galvanometers have
their areas in the ratio of 2: 3 and the
number of turns in the ratio of 4: 5
These two coils carry the same current and are situated in the same field. The
deflections produced by these two coils will be in the ratio of:
( mathbf{A} cdot 8: 15 )
B. 15: 8
c. 8: 1
D. 1: 4
12
377 A loop carrying a current ( i ), lying in the
plane of the paper, is in the field of a
long straight wire with current ( boldsymbol{i}_{0} ) (inward) as shown in figure. If the
torque acting on the loop is given by
( tau=frac{mu_{0} i i_{0}}{x pi r}[sin theta](b-a) . ) Find ( x )
12
378 Magnetic field inside a long solenoid carrying current is:
A. same at all points (uniform)
B. different at poles and at the centre
c. zero
D. different at all points
12
379 The pattern of the magnetic field around a conductor due to an electric
current flowing through it depends on
A. amount of current flowing through the conductor
B. amount of voltage supplied to the conductor
c. size of conductor
D. shape of the conductor
12
380 Two long and parallel straight wires ( A ) and B carrying currents of ( 8.0 mathrm{A} ) and 5.0 A in the same direction are separated by a distance of ( 4.0 mathrm{cm} . ) Estimate the force on a ( 10 mathrm{cm} ) section of wire ( mathrm{A} ) 12
381 A proton is projected with a speed of
( 3 times 10^{6} m / s ) horizontally from east to
west. A uniform magnetic field B of strength ( 2 times 10^{-3} T ) exists in the
vertically upward direction the magnitude of magnetic force on proton is ( boldsymbol{F} times mathbf{1 0}^{-16} boldsymbol{N} ). What is the value of ( boldsymbol{F} ) ?
12
382 The intensity of magnetic induction at the center of a circular coil carrying a current is ( B ). If the number of turns and
radius are doubled, the intensity of
magnetic induction at the center with the same current will be
A ( .2 B )
в. ( 4 B )
( c . B )
D. ( 0.5 B )
12
383 A charged particle with velocity ( 2 times ) ( 10^{3} m / s ) passes undeflected through
electric and magnetic field. Magnetic field is 1.5 tesla. The electric field
intensity would be
A ( cdot 2 times 10^{3} N / C )
в. ( 1.5 times 10^{3} N / C )
c. ( 3 times 10^{3} N / C )
( mathbf{D} cdot 4 / 3 times 10^{-3} N / C )
12
384 charge particles are pictured in the
same magnetic field which points into the screen (represented by blue ( X^{prime} ) s) The particles are moving at the same speeds but in different directions, as
indicated by the red arrows. How do the particles rank, in terms of
the force they experience due to their
movements in the magnetic field, greatest first?
A. 1,2,3
B. 1 and 2 tie, 3
c. 3,1 and 2 tie
D. 3,2,1
E. All tie
12
385 A tightly-wound long solenoid has n turns per unit length,radius r and
carries a current ( i . ) A particle having
charge ( q ) and mass ( m ) is projected from a point on the axis in the direction
perpendicular to the axis.The maximum speed for which particle does not strike
the solenoid will be
A ( cdot frac{mu_{o} q r n i}{2 m} )
B. ( frac{mu_{o} q r n i}{m} )
c. ( frac{2 mu_{o} q r n i}{3 m} )
D. None of these
12
386 Assertion
When radius of a circular loop carrying current is doubled, its magnetic moment becomes four times.
Reason
Magnetic moment depends on the area of the loop.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
387 The magnetic field ( overline{boldsymbol{d} boldsymbol{B}} ) due to a small
current element dl at a distance ( vec{r} ) and
carrying current ‘i’ is
A ( left.cdot frac{mu_{0}}{d B}=frac{frac{d bar{d}}{4 pi} i}{r}right) )
В ( cdot frac{ }{d B}=frac{mu_{0}}{4 pi} i^{2}left(frac{overline{d l} times bar{r}}{r^{2}}right) )
( ^{mathbf{C}} cdot frac{mu_{0}}{d B}=frac{frac{mu}{4 pi} i^{2}}{r} )
D ( cdot frac{mu_{0}}{d B} ileft(frac{overline{d l} times bar{r}}{r^{3}}right) )
12
388 Which of the following is the correct decreasing order of the strengths of four fundamental forces of nature?
A. Electromagnetic force >weak nuclear force>gravitational force>strong nuclear force.
B. Strong nuclear force>weak nuclear force>electromagnetic force>gravitational force
c. Gravitational force>electromagnetic force>strong nuclear force>weak nuclear force
D. strong nuclear force>electromagnetic force>weak nuclear force>gravitational force
12
389 Can a current carrying straight electric wires attract the nearby iron objects
towards them?
12
390 The diagram below represents five
different same-length identical wires(red) carrying the same amount of
current in the same magnetic field (blue) with current directions and
magnetic field directions indicated by
arrows.

Which wire(s) experience(s) the most force due to the magnetic field?
( A cdot 3 ) only
B. 2 only
( c cdot 2 ) and 5
D. 1 only
E. 1 and 4

12
391 The operating magnetic field for accelerating protons in a cyclotron oscillator having frequency of 12 MHz is ( left(q=1.6 times 10^{-19} mathrm{C}, m_{p}=1.67 times 10^{-27}right. )
kg and ( left.1 mathrm{MeV}=1.6 times 10^{-13} mathrm{J}right) )
A . 0.69 न
B . 0.79 न
c. 0.59 न
D. 0.49 ( T )
12
392 An electron moves with a constant
speed v along a circle of radius r. The magnetic moment will be (e is the electron charge)
A . evr
B. ( frac{e v r}{2} )
( mathbf{c} cdot pi r^{2} e v )
D. ( 2 pi r e v )
12
393 Two long parallel conductors carry currents of ( 12 mathrm{A} ) and ( 8 mathrm{A} ) respectively in the same direction. If the wires are 10
cm apart, find where the third parallel
wire also carrying a current must be
placed so that the force experienced by
it shall be zero. Answer in the form of
( x times 10^{-2} m . ) Find ( x )
12
394 Two charges of same magnitude move
in two circles of radii ( boldsymbol{R}_{1}=boldsymbol{R} ) and
( R_{2}=2 R ) in a region of constant
uniform magnetic field ( B_{0} )

The work ( W_{1} ) and ( W_{2} ) done by the
magnetic field in the Two cases,
respectively are such that:
( mathbf{A} cdot W_{1}=W_{2}=0 )
в. ( W_{1}>W_{2} )
( mathbf{c} cdot W_{1}=W_{2} neq 0 )
D. ( W_{1}<W_{2} )

12
395 A square loop of uniform conducting
wire is as shown in figure.A current ( boldsymbol{I} ) (in
ampere) enters the loop from one end
and exits the loop from opposite end as
shown in figure.

The length of one side of square loop is ( l )
meter.The wire has uniform cross-
section area and uniform linear mass
density. The magnetic field is in Tesla and force is in newton.

12
396 A moving coil galvanometer has 48 turns and area of coil is ( 4 times 10^{-2} m^{2} . ) If
the magnetic field is ( 0.2 T, ) then to increase the current sensitivity by ( 25 % ) without changing area (A) and field (B) the number of turns should become:
A . 24
B. 36
( c cdot 60 )
( D cdot 54 )
12
397 A ( H e^{2+} ) ion travels at right angles to a magnetic field of ( 0.80 mathrm{T} ) with a velocity of ( 10^{5} m / s . ) If ( mathrm{M} ) is the magnitude of the
magnetic force on the ion, find ( x ) such that ( boldsymbol{x}=boldsymbol{M} times mathbf{1 0}^{mathbf{1 6}} )
12
398 If a conducting rod of length ( 4 l ) is
rotated about at point ( boldsymbol{O} ) in a uniform
magnetic field ( B ) directed into the
paper and ( D E=l, E A=3 l ), then which
of the folowing is true?
[
begin{array}{rrrrrrrrrr}
times & times & times & times & times & times & times & times & times & times & times \
times & times & times & times & times & times & times & times & times & times & times \
times & times & times & times & times & times & times & times & times & times & times \
times & times & times & times & times & times & times & times & times & times & times \
times & times & times & times & multicolumn{1}{c} {omega_{M}} & times & times & times & times & times \
multicolumn{1}{c} {times} & times & times & times E_{times} & & times & times & times & times & times \
times & times & times & times & times & times & times & times & times & times & times \
times & times & times & times & times & times & times & times & times & times & times \
times & times & times & times & times & times & times & times & times & times & times
end{array}
]
A.
[
V_{A}-V_{E}=frac{9}{2} B omega l^{2}
]
B.
[
V_{E}-V_{A}=frac{9}{2} B omega l^{2}
]
( mathbf{c} )
[
V_{D}-V_{E}=frac{B omega l^{2}}{2}
]
D. ( V_{A}-V_{E}=4 B omega l^{2} )
12
399 A beam of cathode rays is subjected to crossed electric (E) and magnetic fields
(B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by :
( ^{mathbf{A}} cdot frac{B^{2}}{2 v E^{2}} )
B. ( frac{2 v B^{2}}{E^{2}} )
c. ( frac{2 v E^{2}}{B^{2}} )
D. ( frac{E^{2}}{2 v B^{2}} )
12
400 A coil in the shape of an equilateral triangles of side I is suspended between the pole pieces of a permanent magnet such that ( mathrm{B} ) is in plane of the coil. If due to a current i in the triangle, a torque ( tau ) acts on it, the side I of the triangle is :
( ^{mathrm{A}} cdot frac{2}{sqrt{3}}left(frac{tau}{B i}right)^{1 / 2} )
в. ( frac{2}{3}left(frac{tau}{B i}right) )
( ^{c} cdotleft(frac{tau}{sqrt{3} B i}right)^{1 / 2} )
D. ( frac{1}{sqrt{3}} frac{tau}{B i} )
12
401 Find the magnitude and direction of the force vector applied to the loop if the
vector ( vec{p}_{m} ) coincides in direction with
the magnetic field produced by the current ( I ) at the point where the loop is located
A ( cdot vec{F}=-frac{mu_{0} I p_{m}}{pi r^{2}} vec{e}_{r} ; vec{F} uparrow downarrow vec{r} )
B・ ( vec{F}=-frac{mu_{0} I p_{m}}{2 pi r^{2}} overrightarrow{e_{r}} ; vec{F} uparrow downarrow vec{r} )
C・ ( vec{F}=-frac{mu_{0} I p_{m}}{3 pi r^{2}} overrightarrow{e_{r}} ; vec{F} uparrow downarrow vec{r} )
D・ ( vec{F}=-frac{mu_{0} I p_{m}}{4 pi r^{2}} overrightarrow{e_{r}} ; vec{F} uparrow downarrow vec{r} )
12
402 A solenoid has a core of a material with
relative permeability ( 400 . ) The windings of the solenoid are insulated from the
core and carry a current of ( 2 A ).f the
number of turns is 1000 per meter, calculate (a) ( boldsymbol{H} )
(b) ( B ) and
( (c) ) the
magnetising current ( boldsymbol{I}_{m} )
12
403 In a cyclotron, If a deuteron can gain an energy of ( 40 mathrm{MeV} ), then a proton can an
energy of:
A. 40 Mev
B. 80 Mev
c. 20 Mev
D. 160 Mev
12
404 Magnetic filed at point ( ^{prime} boldsymbol{P}^{prime} ) due to both
infinite long current carrying wires is :-
( ^{A} cdot frac{mu_{0}}{2 pi} )
в. ( frac{5 mu_{0}}{6 pi} )
( c cdot frac{5 mu_{0}}{6 pi} mathrm{c} )
‘ ( frac{mu_{0}}{2 pi} ) с
12
405 ( x=0.500 mathrm{m}, y=0.500 mathrm{m}, mathrm{z}=0 ) 12
406 When the face of a coil towards an
observer seems to carry current in direction, north polarity is induced on
that face.
A. electromagnet
B. right angles
c. permanent
D. anticlockwise
12
407 A moving coil galvanometer has a coil of area ( A ) and number of turns ( N . A )
magnetic field B is applied on it. The
torque acting on it is given by ( boldsymbol{tau}=boldsymbol{k} boldsymbol{i} )
where i is current through the coil. If moment of inertia of the coil is I about
the axis of rotation.
If the value of k in terms of
galvanometer parameters ( (mathrm{N}, mathrm{B}, mathrm{A}) ) is given by ( k=x times N B A ). Find ( x )
12
408 A bar magnet, held horizontally, is set into angular oscillations in the earth’s
magnetic field. Its time periods are ( T_{1} )
and ( T_{2} ) at two places where the angles of
dip are ( theta_{1} ) and ( theta_{2} ) respectively. The ratio
of the resultant magnetic fields at these two places will be:
This question has multiple correct options
A. ( T_{1} sin theta_{1}: T_{2} sin theta_{2} )
B. ( T_{mathrm{i}} cos theta_{1}: T_{2} cos theta_{2} )
c. ( T_{2}^{2} sin theta_{2}: T_{1}^{2} sin theta_{1} )
D. ( T_{2}^{2} cos theta_{2}: T_{1}^{2} cos theta_{1} )
12
409 The magnetic field lines inside the solenoid are in the form of
A. parallel straight lines.
B. circular lines.
c. anticlockwise lines.
D. all
12
410 The graph gives the magnitude ( B(t) ) of ( a )
uniform magnetic field that exist throughtout a conducting loop.
perpendicular to the plane of the graph
according to the magnitude of the emf induced in the loop greatest first
A. ( b>(d=epsilon)(d=epsilon)>(a=c) )
c. ( b<d<epsilon<epsilon(a=c)>(d=epsilon) )
12
411 In the statement of Fleming’s left hand rule, what do the direction of centre
finger represents
A. motion
B. magnetic field
c. current
D. none
12
412 A circular coil of 300 turns and
diameter ( 14 mathrm{cm} ) carries a current of 15
A. The magnitude of magnetic moment associated with the loop is?
A . 51.7 J ( T^{-1} )
B . 69.2 J ( T^{-1} )
c. 38.6 J ( T^{-1} )
D. 19.5 J ( T^{-1} )
12
413 The force of repulsion between two
parallel wires is ( boldsymbol{F} ) when each one of
them carries a certain current I. If the
current in each is doubled, the force
between them would be
( A cdot 8 F )
в. ( 4 F )
( c cdot 2 F )
D. ( F )
12
414 A rod of length ( l ) carrying current ( i ) is
kept in uniform magnetic field of
magnitude ( B ) is shown in figure. Then
the force on rod due to magnetic field is:
A. zero
B. ilBsintheta
( mathbf{c} cdot i l B cos theta )
D. ( i l B )
12
415 A wire is bent in the form of a circular
arc with a straight portion ( boldsymbol{A B} )

Magnetic induction at ( O ) when current
is flowing in the wire, is
( ^{text {A } cdot} frac{mu_{0}}{2^{r}}(pi-theta+tan theta) )
в. ( frac{mu_{0} I}{2 pi r}(pi+theta-tan theta) )
c. ( frac{mu_{0} I}{2 pi r}(pi-theta+tan theta) )
D. ( frac{mu_{0} I}{2 pi_{r}}(-tan theta+pi-theta) )

12
416 A coil of moving coil galvanometer
twists through ( 90^{circ} ) when a current of one microampere is passed through it.lf the area of the coil is ( 10^{-4} m^{2} ) and it has
100 turns, calculate the magnetic field of the magnet of the galvanometer.Given ( k=10^{-8} N- )
( boldsymbol{m} / ) degree
12
417 Q Type your question-
respectively as shown in figure.
Assuming that these are placed in the same plane, the magnetic fields will be zero at the centre of the loop when the
separation H is
( A cdot frac{1_{e}}{I_{I} pi} )
В ( cdot frac{I_{c} R}{I_{e}} )
( c cdot frac{pi 1}{I F} )
D. ( frac{1_{e}}{I_{R}} )
12
418 18. In the above question, if the coil is in the magnetic field of
1.2 T, the field being in the plane of coil, then the torque
acting on it is
(a) 1.42 Nm
(b) 2.84 Nm
(c) zero Nm
(d) 0.71 Nm
12
419 What effect did you ignore in your calculation
A. effect of gravity
B. effect of magnetic force
c. effect of electric force
D. ( K E ) of the particle
12
420 An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude
( ^{mathrm{A}} cdot frac{mu_{o} n^{2} e}{r} )
в. ( frac{mu_{o} n e}{2 r} )
c. ( frac{mu_{o} n e}{2 pi r} )
D. zero
12
421 A solenoid of 10 henry inductance and 2 ohm resistance, is connected to a 10
volt battery. In how much the magnetic
energy will be increases to ( 1 / 4 ) th of the maximum value?
A ( .3 .5 mathrm{sec} )
B. 2.5 sec
( c .5 .5 mathrm{sec} )
D. 7.5 sec
12
422 The length of side of a square loop is
4m. This loop is placed in a uniform magnetic field of 2.5 t. Outside the loop, the magnetic field is zero and it is coming out side from magnetic field perpendicularly with velocity ( 2 mathrm{m} / mathrm{s} ). Find the value of induced emf in loop after
one second.
12
423 gauss is equal to
( mathbf{A} cdot 10^{4} T )
B ( cdot 10^{-4} T )
( mathbf{c} cdot 10^{3} T )
D. none of these
12
424 An electron having energy ( 10 e V ) is circulating in a path of radius ( 0.1 m )
having a magnetic field of ( 10^{-4} ) T. The
speed of the electron will be :
A ( .2 .0 timesleft(10^{6}right) m s^{-1} )
B . ( 4.8 timesleft(10^{6}right) m s^{-1} )
c. ( 2.0 timesleft(10^{12}right) m s^{-1} )
D. ( 4.8 timesleft(10^{12}right) m s^{-1} )
12
425 A wire carrying a current of 5 A is placed perpendicular to a magnetic induction of ( 2 mathrm{T} ). The force on each centimeter of
the wire is :
A . ( 0.1 mathrm{N} )
B. 10 N
( c cdot 100 N )
D. 1N
12
426 The formation of a dipole is due to two equal and dissimilar point charges placed at a
A. short distance
B. Iong distance
c. above each other
D. None of these
12
427 A charged particle enters into a uniform magnetic field with velocity vector at an
angle of ( 45^{circ} ) with the magnetic field. The pitch of the helical path followed by the particle is ( p . ) The radius of the helix will
be
A ( cdot frac{p}{sqrt{2} pi} )
B. ( sqrt{2 p} )
c. ( frac{p}{2 pi} )
D. ( frac{sqrt{2 p}}{pi} )
12
428 Three very long straight current carrying conductors are placed parallel to each other as shown in the figure. The conductors ( 1 & 3 ) are fixed where as
conductor 2 is free to move. If the
conductor 2 is pulled towards right through a very small distance ( x, ) find the net force acting on it and angular frequency of the resulting oscillation.
12
429 Which of the three components of
acceleration have non-zero values?
A . ( x ) and ( y )
B. ( y ) and ( z )
c. ( z ) and ( x )
D. ( x, y ) and ( z )
12
430 A conducting rod ( P Q ) of length ( 5 mathrm{m} )
oriented as shown in figure is moving with velocity (2 ( mathrm{m} / mathrm{s} ) ) in rotation in a uniform magnetic field ( (3 hat{j}+4 hat{k}) ) Tesla.
The emf induced in the rod is
A. 32 volts
B. 40 volts
c. 50 volts
D. none
12
431 A current ( I_{1} ) carrying wire ( A B ) is placed
near another long wire CD carrying
current ( I_{2} ). If wire ( A B ) is free to moves, it
will have:
A. rotational motion only
B. translational motion only
c. rotational as well as translational motion
D. neither rotational nor translational motion
12
432 Assertion
To protect any instrument from external magnetic field, it is put inside an iron body.
Reason
Iron is a magnetic substance.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
433 Figure shows an Amperian path
( A B C D A ). Part ( A B C ) is in verical plane
PSTU while part ( C D A ) is in horizontal
plane ( P Q R S ). Direction of circulation along the path is shown by an arrow
near point ( B ) and ( D ) ( oint vec{B} cdot d vec{l} ) for this path according to
Ampere’s law will be:
( mathbf{A} cdotleft(I_{1}-I_{2}+I_{3}right) mu_{0} )
B・ ( left(-I_{1}+I_{2}right) mu_{0} )
( mathrm{c} cdot I_{3} mu_{0} )
( mathbf{D} cdotleft(I_{1}+I_{2}right) mu_{0} )
12
434 The Biot Savart’s Law in vector form is
( ^{mathrm{A}} cdot_{overline{delta B}}=frac{mu_{0}}{4 pi} frac{d l(vec{l} times vec{r})}{r^{3}} )
B・ ( _{overline{delta B}}=frac{mu_{0}}{4 pi} frac{I(bar{d} l times vec{r})}{r^{3}} )
( ^{mathbf{C}} cdot frac{mu_{0}}{delta B}=frac{I(vec{r} times overrightarrow{d l})}{4 pi} frac{r^{3}}{ } )
D ( cdot frac{ }{delta B}=frac{mu_{0}}{4 pi} frac{I(vec{d} l times vec{r})}{r^{2}} )
12
435 An electron does not suffer any
deflections while passing through a region. This makes sure that there is no
magnetic field in that region. Is the
given statement true or false?
12
436 A vertical wire carries a current in
upward direction. An electron beam sent horizontally towards the wire will be deflected (gravity free space):
A. towards right
B. towards left
c. upwards
D. downwards
12
437 The magnetic moment ( (mu) ) of a revolving electron around the nucleus varies with
principal quantum number ( n ) as :
A. ( mu propto 1 / n )
В ( cdot mu propto 1 / n^{2} )
c. ( mu propto n )
D. ( mu propto n^{2} )
12
438 The magnetic field inside a long straight solenoid carrying current:
A . Is zero
B. Decreases as we move towards its end
c. Increases as we move towards its end
D. Is same at all points
12
439 An electron revolving in an orbit of radius ( 0.5 dot{A} ) in a hydrogen atom executes ( 10^{16} ) revolutions per second.
The magnetic moment of electron due to its orbital motion will be
A. ( 1.256 times 10^{-23} mathrm{Am}^{2} )
B. ( 653 times 10^{-26} mathrm{Am}^{2} )
c. ( 10^{-3} ) Am ( ^{2} )
D. ( 256 times 10^{-26} mathrm{Am}^{2} )
12
440 An electron and a proton each travel
with equal speeds around circular
orbits in the same uniform magnetic field as indicated (not to scale) in fig.
The field is into the page on the
diagram. The electron travels …. around
the ( ldots . ) circle and the proton travels… around the ( ldots . ) circle
A. clockwise, smaller, counterclockwise, larger
B. counterclockwise, larger, counterclockwise, smaller
c. clockwise, larger, counterclockwise, smaller
D. counterclockwise, larger, clockwise, smaller
12
441 A proton, a deutron and an ( alpha ) -particle with same kinetic energy enter perpendicularly in a uniform magnetic
field, then the ratio of radii of their
circular paths is
B . ( sqrt{2}: 1: 1 )
c. ( 1: sqrt{2}: 1 )
D. ( 1: 2: sqrt{2} )
12
442 Obtain the expression for the deflecting torque acting on the current carrying rectangular coil of a galvanometer in a uniform magnetic field. Why is a radial magnetic field employed in the moving coil galvanometer? 12
443 Write Ampere’s circuital law. Obtain an expression for magnetic field on the axis of current carrying very long solenoid. Draw necessary diagram. 12
444 An electron in a circular orbit of radius
( 0.5 A^{o} ) makes ( 7 times 10^{15} ) revolutions in
each second. This electron orbit is
equivalent to a magnetic shell of moment ( (text { in } A m) )
A. ( 88 times 10^{-25} )
B . ( 8.89 times 10^{-25} )
c. ( 44 times 10^{-25} )
D. 4.4 ( times 10^{-25} )
12
445 For a given distance from a current
element, the magnetic induction is
maximum at an angle measured with
respect to axis of the current. The angle
is :
A ( cdot frac{3 pi}{4} )
B. ( frac{pi}{4} )
c. ( frac{pi}{2} )
D. ( 2 pi )
12
446 An ( alpha ) particle is moving along a circle of radius ( R ) with a constant angular velocity ( omega . ) Point ( A ) lies in the same
plane at a distance ( 2 R ) from the centre.
Point ( A ) records magnetic
field produced by ( alpha ) particle. If the minimum time interval between two successive times at which ( A ) records
zero magnetic field is ( ^{prime} t^{prime}, ) the angular
speed ( omega, ) in terms of ( t ) is
A ( cdot frac{2 pi}{t} )
в. ( frac{2 pi}{3 t} )
c. ( frac{pi}{3 t} )
D. ( frac{pi}{t} )
12
447 A charged particle of mass ( m ) and charge ( q ) is accelerated through a potential difference of ( V ) volt. It enters a
region of uniform magnetic field which is directed perpendicular to the direction of motion of the particle. The particle will move on a circular path of
radius given by
A ( cdot frac{V m}{q B^{2}} )
B. ( frac{2 V m}{q B^{2}} )
c. ( sqrt{frac{2 V m}{q}} cdotleft(frac{1}{B}right) )
D. ( sqrt{frac{V m}{q}} cdotleft(frac{1}{B}right) )
12
448 Assertion
A rectangular current loop is in an arbitrary orientation in an external
uniform magnetic field. No work is
required to rotate the loop about an axis
perpendicular to its plane.
Reason
All positions represent the same level of
energy.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
449 Choose the correct statements:
This question has multiple correct options
A. For a closed surface, the surface integration ( oint vec{B} cdot overrightarrow{d s} ) is always zero, where ( vec{B} ) is magnetic field
B. A current carrying circular loop is in a uniform external magnetic field and is free to rotate about its
diametrical axis will be in stable equilibrium when flux of total magnetic field (external field + field due to the
loop itself) is maximum.
C . Spectral energy distributed graph of a black body is shown in figure. If temperature (in ( mathrm{K} ) ) of the black body is
doubled and surface area is halved, the area under the
graph will be eight times.
D. In keplers third law, ( frac{T^{2}}{R^{3}} ) depends on the mass of the
Sun, around which a planet is revolving.
12
450 A short bar magnet of magnetic
moment ( 0.4 J T^{-1} ) is place in a uniform
magnetic field of 0.16 T. The magnet is stable equilibrium when the potential energy is
( mathbf{A} cdot-0.064 J )
B. zero
c. ( -0.082 J )
D. 0.064
12
451 A particle of mass ( M ) and charge ( Q )
moving with velocity ( vec{v} ) describe a
circular path of radius ( R ) when subjected to a uniform transverse
magnetic field of induction ( boldsymbol{B} ). The work
done by the field when the particle completes one full circle is:
( ^{mathbf{A}} cdotleft(frac{M v^{2}}{R}right)^{2 pi R} )
B. zero
с. ( B Q 2 pi R )
D. ( B Q v 2 pi R )
12
452 State the rule to determine the
direction of current induced in a coil
due to its rotation in a magnetic field.
12
453 A closely wound solenoid of 800 turns and area of cross-section ( 2.5 times 10^{-4} m^{2} )
carries a current of ( 3.0 A ). Explain the
sense in which the solenoid acts line a
bar magnet. What is its associated
magnetic moment?
( mathbf{A} cdot 6 J / T )
в. ( 0.9 J / T )
c. ( 9 J / T )
D. ( 0.6 J / T )
12
454 A straight conductor carries a current.
Assume that all free electrons in the
conductor move with the same drift
velocity ( v . A ) and ( B ) are two observers on
a straight line ( X Y ) parallel to the conductor. A is stationary. B moves along XY with a velocity ( v ) in the
direction of the free electrons:
A. A and B observe the same magnetic field
B. A observes a magnetic field, B does not
C. A and B observe magnetic fields of the same magnitude but opposite directions
D. A and B do not observe any electric field
12
455 Two parallel wires carrying currents in
the same direction attract each other
because of
A. potential difference between them
B. mutual inductance between them
c. electric forces between them
D. magnetic forces between them
12
456 Whend ( approx a ) but wires are not touching
the loop, it is found that the net magnetic field on the axis of the loop is
zero at a height ( h ) above the loop. In that
case :
A. Current in wire 1 and wire 2 is in the direction PQ and RS, respectively such ( h approx a )
B. Current in wire 1 and wire 2 is in the direction PQ and
SR, respectively and ( h approx a )
c. current in wire 1 and wire 2 is in the direction PQ and SR, respectively and ( h approx 1.2 a )
D. Current in wire 1 and wire 2 is in the direction PQ and
RS, respectively and ( h approx 1.2 a )
12
457 The radius of the curved part of the wire is ( R, ) the linear parts are assumed to be
very long. Find the magnetic induction of the field at the point ( O ) if a currentcarrying wire has the shape shown in
figure above.
A ( cdot B=frac{3 mu_{0}}{4} frac{i}{R} )
В. ( B=frac{mu_{0}}{2} frac{i}{R} )
c. ( _{B}=frac{2 mu_{0}}{3} frac{i}{R} )
D. ( B=frac{mu_{0}}{4} frac{i}{R} )
12
458 If ( mathrm{E} ) and ( mathrm{B} ) denote electronic and
magnetic field respectively, which of the following is dimensionless?
A ( cdot sqrt{mu_{0} varepsilon_{0}} frac{E}{B} )
в. ( quad mu_{0} varepsilon_{0} frac{E}{B} )
( ^{mathbf{c}} cdot_{mu_{0} varepsilon_{0}}left(frac{B}{E}right)^{2} )
D. ( frac{E}{varepsilon_{0}} frac{mu_{0}}{B} )
12
459 Two long parallel wires are at a distance of 1 metre. Both of them carry one
ampere of current. the force of
attraction per unit length between the two wires is
A ( cdot 2 times 10^{-7} mathrm{Nm}^{-1} )
В. ( 2 times 10^{-8} N m^{-1} )
c. ( 5 times 10^{-8} mathrm{Nm}^{-1} )
D. ( 10^{-7} N m^{-1} )
12
460 Derive the formula for the force acting between two parallel current carrying
conductors.
12
461 An electron having charge ( 1.6 times 10^{-19} mathrm{C} )
and mass ( 9 times 10^{-31} mathrm{kg} ) is moving with
( 4 times 10^{6} mathrm{m} / mathrm{s} ) speed in a magnetic field
of ( 2 times 10^{-1} ) tesla in a circular orbit. The
force acting on an electron and the radius of circular orbit will be:
A ( cdot 1.28 times 10^{-14} N, 1.1 times 10^{-3} m )
B . ( 1.28 times 10^{15} N, 1.2 times 10^{-12} m )
C . ( 1.28 times 10^{-13} N, 1.2 times 10^{-4} mathrm{m} )
D. none of these
12
462 Assertion
A stationary charged particle in a magnetic field does not experience a force.
Reason
The force acting on a charged particle does not depend on velocity of the
particle
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
463 Two particles ( X ) and ( Y ) having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field
and describe circular paths or radii ( boldsymbol{R}_{1} )
and ( R_{2} ) respectively. The ratio of mass
of ( X ) to that of ( Y ) is equal to:
( ^{mathbf{A}} cdotleft(frac{R_{1}}{R_{2}}right)^{2} )
B. ( left(frac{R_{1}}{R_{2}}right) )
( ^{mathbf{C}} cdotleft(frac{R_{1}}{R_{2}}right)^{1 / 2} )
D. ( frac{R_{2}}{R_{1}} )
12
464 A horizontal overhead power line carries a current of ( 90 mathrm{A} ) in east to west
direction. Magnitude of magnetic field due to the current ( 1.5 mathrm{m} ) below the line is
A . 1.27
в. ( 1.2 times 10^{-10} T )
c. ( 0 T )
D. ( 1.2 times 10^{-5} T )
12
465 Assertion
Cyclotron does not accelerate electron.
Reason
Mass of the electrons is very small.
A. Both Assertion and Reason are correct and Reason is
the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
466 An electron of charge ( e ) moves in a
circular orbit of radius ( r ) around a
nucleus the magnetic field due to orbit motion of the electron at the site of the
nucleus is ( B ). The angular velocity ( omega ) of
the electron is:
A ( cdot omega=frac{mu_{0} e B}{4 pi r} )
B. ( omega=frac{mu_{0} e B}{pi r} )
c. ( _{omega=frac{4 pi r B}{mu_{0} e}} )
D. ( omega=frac{2 pi r B}{mu_{0} e} )
12
467 State the principle of moving coil galvanometer? 12
468 State Fleming’s left hand rule. 12
469 A ( 0.5 m ) long straight wire in which a
current of ( 3.2 A ) is flowing is kept at right angle to a uniform magnetic field
of ( 2.0 T . ) The force acting on the wire will
be:
A ( .2 N )
в. 2.4 и
( c .3 .2 N )
D. 3N
12
470 By inserting a soft iron piece into a solenoid, strength of the magnetic field
A. increases
B. decreases
c. first increases then decreases
D. remains unchanged
12
471 Ampere’s circuital law holds good for:
A. conduction current only
B. displacement current only
C. both conduction current and displacement current
D. none of these
12
472 A current carrying conducting square frame of side I carrying current lis
placed in a uniform transverse magnetic field ( vec{B} ) as shown in the figure.
Choose the incorrect statement.
A. Magnitude of force on the frame is ( 4 I B l )
B. Magnitude of torque on the frame ( I l^{2} B )
C. Torque on the frame is zero
D. Both (1) and (2)
12
473 A horizontal wire ( 0.1 mathrm{m} ) long carries a current of 5 A. Find the magnitude of the magnetic field, which can support the weight of the wire. Assume wire to be of ( operatorname{mass} 3 times 10^{-3} k g m^{-1}: )
A ( .5 .88 times 10^{-2} T )
B . ( 4.88 times 10^{-3} T )
( mathbf{c} .5 .88 times 10^{-3} T )
D. ( 5.88 times 10^{-4} T )
12
474 The magnetic force on a moving charge
in a magnetic field acts
A. Only at right angles to the direction of motion of the particle.
B. Only at right angles to magnetic field.
C. At right angles to the field and the direction of motion of the particle.
D. Parallel to the field as well as the direction of motion
of the particle.
12
475 A galvanometer of resistance ( 50 Omega ) is
connected to a battery of ( 3 V ) along with a resistance of ( 2950 Omega ) in series shown,
full-scale deflection of 30 divisions. The
additional series resistance required to reduce the deflection to 20 divisions is
A . ( 4440 Omega )
B. 1500Omega
c. ( 7400 Omega )
D. ( 2950 Omega )
12
476 If current in the coil decreases, then strength of the magnetic field
A. decreases
B. increases
c. sometimes decreases and sometimes increases
D. remains unchanged
12
477 A current carrying loop is placed in a
uniform magnetic field in four different
orientations as shown in figure. Arrange them in the decreasing order of
potential energy
( widehat{Q} )
2
3
A. 4,2,3,1
В. 1,4,2,3
( mathbf{c} cdot 4,3,2,1 )
D. 1,2,3,4
12
478 ( L ) is circular loop carrying a current. ( boldsymbol{P} )
is a point on its axis ( O X . d l ) is an
element of length on the loop at a point
( A ) on it. The magnetic field at ( P: )
This question has multiple correct options
A. due to ( L ) is directed along ( O X )
B. due to dl is directed along ( O X )
c. due to dl is perpendicular to ( O X )
D. due to dl is perpendicular to ( A P )
12
479 Factors which govern the force experienced by a current carrying conductor placed in a uniform magnetic field depends on
A. strength of the magnetic field in which conductor is placedd
B. strength of current flowing through the conductor.
c. length of conductor.
D. all
12
480 An ideal solenoid having 5000 turns ( / m )
has an aluminium core and carries a
current of ( 5 A . ) If ( chi_{A l}=2.3 times 10^{-5}, ) then
the magnetic field developed at center will be
A. ( 0.031 T )
( T )
в. ( 0.048 T )
c. 0.0277
D. ( 0.050 T )
12
481 It two parallel wires carry current in
opposite directions
A. The wires attract each other
B. The wires repel each other
C. The wires experience neither attraction nor repulsion
D. The forces of attraction or repulsion do not depend on current direction
12
482 A moving coil galvanometer A has 200
turns and resistance ( 100 . ) Another
meter ( mathrm{B} ) has 100 turns and resistance
( 40 . ) All the other quantities are same in both the cases. The current sensistivity of
A. B is double as that of A
B. A is 2.5 times of B
c. A is 5 times of B
D. B is 5 times of A
12
483 In Thomsons method, electric field of
intensity ( boldsymbol{E}, ) magnetic field of induction
( B ) and velocity ( V ) of the electrons were in mutually perpendicular directions. The condition for velocity is
A. ( V=E / B )
в. ( V=B / E )
c. ( V=B E )
D. ( V=sqrt{B / E} )
12
484 If two protons are moving with speed ( boldsymbol{v}=mathbf{4 . 5} times mathbf{1 0}^{mathbf{5}} mathbf{m} / mathrm{s} ) parallel to each other
then find the ratio of electrostatic and
magnetic force between them?
( mathbf{A} cdot 4.4 times 10^{5} )
В. ( 2.2 times 10^{5} )
c. ( 3.3 times 10^{5} )
D. ( 1.1 times 10^{5} )
12
485 The magnetic field at the center of a
long circular coil carrying current will
be:
A. parabolic lines
B. circular lines
c. parallel straight lines
D. perpendicular straight lines
12
486 In the figure shown a circular current carrying conductor lies in yz plane and
its centre is at point O.If ( B_{A} ) and ( B_{B} ) are
the
A ( . B_{A}=B_{B} )
В. ( B_{A}>B_{B} )
c. ( B_{A}<B_{B} )
D. None of these
12
487 A current I flows in a infinitely long wire with cross section in the form of a
semicircular ring of radius R. The magnitude of the magnetic induction at its axis is
A ( cdot frac{mu_{0} I}{pi^{2} R} )
в. ( frac{mu_{0} mathrm{I}}{2 pi^{2} mathrm{R}} )
c. ( frac{mu_{0} mathrm{I}}{2 pi mathrm{R}} )
D. ( frac{mu_{0} I}{4 pi mathrm{R}} )
12
488 toppr ( t )
Q Type your question
magnetic force acting on each wire?
( A )
B.
( c )
D.
E. There is no net force acting on either wire
12
489 A charged particle entering a magnetic
field from outside in a direction
perpendicular to the field
A. can never complete one rotation inside the field
B. may or may not complete one rotation in the field depending on its angle of entry into the field
c. will always complete exactly half of a rotation before leaving the field
D. may follow a helical path depending on its angle of entry into the field
12
490 What is a solenoid? Draw the pattern of magnetic field lines of
(i) A current carrying solenoid and
(ii)A bar magnet. List two distinguishing features between the
two fields.
12
491 A current of ( 10^{-7} ) ampere produces 50
division deflection in a galvanometer. Then its figure of merit will be
A ( cdot 10^{-4} ) amp ( / d i v )
B . ( 10^{-8} ) amp / div
( mathbf{c} cdot 10^{-10} mathrm{amp} / mathrm{div} )
D. ( 2 times 10^{-9} ) amp/div
12
492 A current of ( 1 mathrm{A} ) is flowing along positive x-axis through a straight wire of length ( 0.5 mathrm{m} ) placed in a region of a magnetic field given by ( vec{B}=(2 hat{i}+4 hat{j}) ) T. The magnitude and the direction of the force experienced by the wire
respectively are:
A ( cdot sqrt{18} N, ) along positive z-axis
B. ( sqrt{20} N ), along positive ( x ) -axis
c. ( 2 N, ) along positive z-axis
D. ( 4 N ), along positive y-axis
12
493 State Biot-Savart law. 12
494 The total momentum of electrons in a
straight wire of length ( l=1000 m )
carrying a current ( mathrm{I}=mathbf{7} mathbf{0} boldsymbol{A}, ) will be (in
( N-s) )
A . ( 0.40 times 10^{-6} )
B. ( 0.20 times 10^{-6} )
c. ( 0.80 times 10^{-6} )
D. ( 0.16 times 10^{-6} )
12
495 When a magnet M is pushed in and out
of a circular coil ( C ) connected to a very
sensitive galvanometer ( G ) as shown in
the figure with frequency f then which of
the following holds true?
A. constant deflection will be observed in the galvanometer.
B. visible small variation will be observed in the galvanometer if ( f ) is about 50 Hz
c. oscillation in the deflection will be seen clearly when ( f=1 ) or ( 2 mathrm{Hz} )
D. no variation in the deflection will be seen even when ( f=1 ) or 2 Hz.
12
496 A particle of charge ( q ) and mass ( m ) is moving through a region of space where crossed magnetic and electric fields produce a zero net force on the charge. At a later time, the Electric field is
reduced by a factor of two. What effect will this have on the motion
of the particle? Select all that apply.
A. The particle will continue to move in a circle of the same radius.
B. The particle will eventually move in a circle of twice the radius
C. The particle will eventually move in a circle of half the radius
D. The particle will eventually follow a curved-noncircular path
E. The particle will follow a straight line path.
12
497 If a charged particle goes unaccelerated in a region containing electric and magnetic fields:
A . ( vec{E} ) must be parallel to ( vec{B} )
B. ( bar{V} ) must be perpendicular to Electric field
c. ( vec{V} ) must be parallel to ( vec{B} )
D. ( E ) must be equal to ( v B )
12
498 An insulating rod of length ( l ) carries a charge ( q ) distributed uniformly on it. The rod is pivoted at its mid-point and is rotated at a frequency ( f ) about a fixed axis perpendicular to the rod and passing through the pivot. The magnetic moment of the rod system is
A ( cdot frac{1}{12} pi q f l^{2} )
В . ( pi q f l^{2} )
c. ( frac{1}{6} pi q f l^{2} )
D. ( frac{1}{3} pi q f l^{2} )
12
499 What is a solenoid? 12
500 (i) Why does a current carrying, freely suspended solenoid rest along a particular direction?
(ii) State the direction in which it rests.
12
501 Energy associated with an electric field
is analogous to whereas the
energy associated with the magnetic field is analogous to
A. kinetic energy, potential energy
B. potential energy, potential energy
c. potential energy, kinetic energy
D. kinetic energy, kinetic energy
12
502 In a circular coil (1) of radius ( boldsymbol{R} ), current
( I ) is flowing and in another coil (2) of
radius ( 2 R ) a current ( 2 I ) is flowing, then the ratio of the magnetic fields produced by the two coils is
A . 1:
B. 2:
c. 1: 2
D. 3:
12
503 A current of ( 0.6 A ) produces a deflection of 30 in the tangent galvanometer. Calculate the value of current will
produce a deflection of 60
A. ( 1.2 mathrm{A} )
в. 1.8 А
c. 2.4 А
D. 3.0 A
12
504 A very high magnetic field is applied to a stationary charge. Then, the charge experiences
A. A force in a direction of magnetic field
B. A force perpendicular to the magnetic field
c. A force in an arbitrary direction
D. No force
12
505 A cylindrical conducting rod is kept with its axis along positive z-axis, where a uniform magnetic field exists parallel to z-axis. The current induced in
the cylinder is
A. zero
B. clockwise as seen from +z-axis
c. anti-clockwise as seen from +z-axis
D. opposite to the direction of magnetic field
12
506 Two parallel wires ( 2 mathrm{m} ) apart carry currents of 2 A and 5 A respectively in the same direction, the force per unit
length acting between these two wires is:
A ( cdot 2 times 10^{-6} mathrm{N} mathrm{m}^{-1} )
В. 3 ( times 10^{-6} mathrm{N} mathrm{m}^{-1} )
c. ( 1 times 10^{-6} mathrm{N} mathrm{m}^{-1} )
D. ( 4 times 10^{-6} mathrm{N} mathrm{m}^{-1} )
12
507 A helium nucleus (charge ( +2 e ) ) completes one round of a circle of
radius ( 0.8 m ) in 2 sec. Find the magnetic field at the centre of the circle.
12
508 STATEMENT-1: A Solenoid tend to
contract (along its length) when a current is passed through it. STATEMENT-2: If current in two coaxial
circular rings of equal radii is in same sense( as seen by an observer on axis away from both the rings), the rings
attract each other. Further the given current carrying rings attract each other because parallel current attracts.
A. Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-
B. Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-
c. Statement-1 is True, Statement-2 is False
D. Statement-1 is False, Statement-2 is True
12
509 Complete the given statement, the
strength of an electromagnet can be:
A. increased by adding a ferromagnetic core
B. decreased by adding turns of wire to the coil
C. increased by reducing the current through the wire
D. increased by adding an aluminum core
E. decreased by adding more layers of wire to the coil
12
510 A straight wire of length ( 50 mathrm{cm} ) carrying
a current of ( 2.5 A ) is suspended in mid-
air by a uniform magnetic field of ( 0.5 T )
(as shown in figure). The mass of the
wire is ( left(boldsymbol{g}=mathbf{1 0 m} / boldsymbol{s}^{2}right) )
( mathbf{A} cdot 100 g m )
В. ( 125 g m )
( mathbf{c} cdot 62.5 g m )
D. ( 250 g m )
12
511 A toroid wound with 100 turns/m of wire
carries a current of ( 3 A ). The core of
toroid is made of iron having relative
magnetic permeability of ( mu_{r}=5000 ) under given conditions. The magnetic field inside the iron is
( left(text { Take } mu_{o}=4 pi times 10^{-7} T m A^{-1}right) )
A ( .0 .15 T )
в. ( 1.5 times 10^{-2} T )
c. ( 0.47 T )
D. ( 1.88 T )
12
512 Consider six wires into or out of the
page, all with the same current. Rank the line integral of the magnetic field(from most positive to most
negative) taken counterclock wise around each loop shown as positive in accordance with right hand screw rule.
( mathbf{A} cdot B>C>D>A )
В . ( B>C=D>A )
c. ( B>A>C=D )
D. ( C>B=D>A )
12
513 A galvanometer coil ( 5 mathrm{cm} times 2 mathrm{cm} ) with 200 turns is suspended vertically in a field of ( 5 times 10^{-2} ) T.The suspension fibre
needs a torque of ( 0.125 times 10^{-7} N-m )
to twist it through one radian. If ( i ) is the
strength of the current required to be maintained in the coil when we require
a deflection of ( 6^{circ} ) then find ( x ) such that
( boldsymbol{x}=boldsymbol{i} times mathbf{1 0}^{8} )
12
514 The direction of magnetic lines of forces close to a straight conductor carrying current will be –
A. A long the length of the conductor
B. Radially outward
c. circular in a plane perpendicular to the conductor
D. Helical
12
515 Maximum iron filings stick to the middle of a bar magnet when it is brought near them.
A. True
B. False
12
516 The magnetic field at ( O ) due to current
in the wire segment BC of the infinite wire forming a loop as shown in figure
is
( ^{A} cdot frac{mu_{0} I}{4 pi d}left(cos phi_{1}+cos phi_{2}right) )
в. ( frac{mu_{0}}{4 pi} )
c. ( frac{mu_{0} I}{4 pi d}left(sin phi_{1}+sin phi_{2}right) )
D. ( frac{mu_{0}}{4 pi} )
12
517 A galvanometer, with a scale divided into 100 equal divisions, has a current
sensitivity of 10 div per ( mathrm{m} mathrm{A} ) and voltage sensitivity 2 div per ( mathbf{m V} ). To read ( 5 A ) full scale deflection
A. Shunt resistance should be ( 1 Omega )
B. Shunt resistance should be ( 0.1 Omega )
c. shunt resistance should be ( 0.01 Omega )
D. Shunt resistance should be ( 0.001 Omega )
12
518 Find the magnetic field due to
conducting wire at point ( O, ) at centre of
semicircle of radius ( r ) and carrying a
current ( i ) as shown in the figure.
( ^{A} cdot frac{mu_{0}}{4 r} )
в. ( frac{mu_{0} i}{4 r}(1+2 pi) )
c. ( frac{mu_{0} i}{4 r}(pi-2) )
D. ( frac{mu_{0} i}{4 pi r}(pi+2) )
12
519 A moving coil galvanometer has resistance ( 50 Omega ) and it indicates full
deflection at ( 4 m A ) current. A voltmeter
is made using this galvanometer and a 5k. ( Omega ) resistance. The maximum voltage
that can be measured using this voltmeter, will be close to:
A . ( 10 V )
B. 20V
c. ( 40 V )
D. ( 15 V )
12
520 If a copper rod carries a direct current, the magnetic field associated with the current will be:
A. only inside the rodd
B. only outside the rod
c. both inside and outside the rod
D. neither inside nor outside the rod
12
521 A proton moves with a speed of ( 5.0 times ) ( 10^{6} mathrm{m} / mathrm{s} ) along the ( mathrm{x} ) -axis. It enters a
region where there is a magnetic field of magnitude ( 2.0 . ) Tesla directed at an
angle of ( 30^{circ} ) to the ( x ) -axis and lying in the xy-plane. The magnitude of the magnetic force on the proton is?
A. ( 0.8 times 10^{-13} mathrm{N} )
В. ( 1.6 times 10^{-13} mathrm{N} )
c. ( 8.0 times 10^{-13} mathrm{N} )
D. ( 8.01 times 10^{-13} mathrm{N} )
E ( .16 times 10^{-13} mathrm{N} )
12
522 If a charged particle projected in a gravity-free room deflects, then
A. there must be an electric field
B. there must be a magnetic field
c. both fields cannot be zero
D. none of these
12
523 Assertion
The bar magnet falling vertically along
the axis of the horizontal coil will be
having acceleration less than ( g )
Reason
Clockwise current induced in the coil.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
524 Conisder a block of conducting material
of resistivity ( rho ) shown in fig., Current
enters at ( A ) and leaves at ( D )

For current entering at ( A, ) the electric
field at a distance ‘r’ from A is??
A ( cdot frac{rho l}{8 pi r^{2}} )
B. ( frac{rho l}{r^{2}} )
c. ( frac{rho l}{2 pi r^{2}} )
D. ( frac{rho l}{4 pi r^{2}} )

12
525 A magnetic moment of an electron orbiting in a circular orbit of radius ( r )
with a speed ( v ) is equal to:
A ( cdot frac{e v r}{2} )
в. ( e v r )
c. ( frac{e r}{2 v} )
D. none of these
12
526 Figure shows an equilateral triangle
( A B C ) of side ( l ) carrying currents as
shown, and placed in a uniform magnetic field ( B ) perpendicular to the
plane of triangle. The magnitude of magnetic force on the triangle is
A . il
B. 3il
( c .2 i l )
D. zer
12
527 A conductor ( A B ) carries a current ( i ) in a magnetic field ( vec{B} . ) If ( overrightarrow{A B}=vec{r} ) and the force on the conductor is ( vec{F} ). Then
This question has multiple correct options
A ( cdot vec{F} ) does not depend on the shape of ( A B )
В ( cdot vec{F}=i(vec{r} times vec{B}) )
c. ( vec{F}=i(vec{B} times vec{r}) )
D ( cdot|vec{F}|=i(vec{r} cdot vec{B}) )
12
528 A straight wire of 0.3 m carrying a current of ( 2 mathrm{A} ) in the downward direction
is placed in a magnetic field of ( 0.1 mathrm{T} ) as shown in the figure. Find out the magnitude of the force on the wire?
A . ( 0.06 N )
B. 2.0 N
c. ( 6.7 mathrm{N} )
D. 0.15N
E. 0.015N
12
529 A current carrying wire and a
rectangular loop are placed as shown in
figure then
A. The wire will be repelled by the rectangular loop
B. The wire will attracted by the rectangular loop
c. There will not be any change in position of wire
D. Loop will rotate
12
530 A charged oil drop weighing ( 1.6 times ) ( 10^{-15} N ) is found to remain suspended
in a uniform electric field of intensity
( 2 times 10^{3} N C^{-1} . ) Find the charge on the
drop.
12
531 State and explain Biot-Savart Law. 12
532 Current of 10 ampere and 2 ampere are passed through two parallel wires A and
B, respectively in opposite directions. If the wire ( A ) is infinitely long and the length of the wire ( mathrm{B} ) is ( 2 mathrm{m} ), the force on the conductor ( B ) which is situated at 10
( mathrm{cm} ) distance from A will be
( mathbf{A} cdot 8 times 10^{-5} N )
B ( cdot 4 times 10^{-5} N )
c. ( 8 pi times 10^{-7} N )
D. ( 4 pi times 10^{-7} N )
12
533 Two concentric circular coils ( X ) and ( Y ) of
radii ( 16 mathrm{cm} ) and ( 10 mathrm{cm}, ) respectively, lie in the same vertical plane containing the north to south direction. Coil X has
20 turns and carries a current of ( 16 mathrm{A} )
coil ( Y ) has 25 turns and carries a current
of 18 A. The sense of the current in ( X ) is
anticlockwise, and clockwise in ( Y ), for an observer looking at the coils facing west. Give the magnitude and direction of the net magnetic field due to the coils at their centre
12
534 The electric and magnetic field differ in
that :
A. the electric lines of force are closed curves, while magnetic field lines are not
B. the magnetic field lines are closed, while electric lines are not
C. the electric lines can give direction of electric field, while magnetic lines cannot
D. the magnetic lines can give direction of magnetic field, while electric lines cannot
12
535 The force of repulsion between two
parallel wires is ( f ) when each one of
them carries a certain current I. If the
current in each is doubled, the force
between them would be
A. ( 4 / f )
B. ( 4 f )
( c cdot 2 f )
D. ( f )
12
536 n fig, there is a uniform conducting
structure in which each small square
has side ( a ). The structure is kept in a
uniform magnetic field ( B ). Then the
magnetic force on the structure will be:
( A cdot 2 sqrt{2} i B a )
B. ( sqrt{2} i ) Ва ( a )
( c .2 i B a )
D. ( i B a )
12
537 An electric charge in uniform motion produces:
A. an electric field only
B. a magnetic field only
c. both electric and magnetic fields
D. no such field at all
12
538 If in a circular coil A of radius R, current
is flowing and in another coil B of radius ( 2 mathrm{R} ) a current 2 I is flowing, then
the ratio of the magnetic fields ( B_{A} ) and
( mathrm{B}_{B}, ) produced by them will be
A
B. 2
( c cdot 1 / 2 )
D. 4
12
539 The following diagram in figure shows a
fixed coil of several turns connected to a
centre zero galvanometer ( G ) and ( a )
magnet NS which can move in the
direction shown in the
diagram. Describe the observation in
the galvanometer if the magnet is moved rapidly towards the coil.
12
540 An electron ( left(operatorname{mass}=9.1 times 10^{-31}right. )
charge ( left.=-1.6 times 10^{-19} mathrm{C}right) ) experiences
no deflection if subjected to an electric field of ( 3.2 times 10^{5} V / m ) and a magnetic
field of ( 2.0 times 10^{-3} mathrm{Wb} / mathrm{m}^{2} . ) Both the
fields are normal to the path of electron and to each other. Ifthe electric field is
removed, then the electron will revolve in an orbit of radius:
A . ( 45 mathrm{m} )
в. 4.5 т
c. ( 0.45 m )
D. ( 0.045 mathrm{m} )
12
541 A current loop consists of two identical
semicircular parts each of radius ( mathrm{R} ), one
lying in the ( x ) -y plane and the other in ( x-z )
plane. If the current in the loop is i., the
resultant magnetic field due to the two
semicircular parts at their common
centre is
A ( cdot frac{mu_{0} i}{sqrt{2} R} )
В. ( frac{mu_{0} i}{2 sqrt{2} R} )
c. ( frac{mu_{0} i}{2 R} )
D. ( frac{mu_{0} i}{4 R} )
12
542 Assertion
A stationary charged particle in a magnetic field does not experience a force.
Reason
The force acting on a charged particle does not depend on velocity of the
particle
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
543 In a coaxial, straight cable, the central conductor and the outer conductor
carry equal currents in opposite directions. The magnetic field is zero:
A. outside the cable
B. inside the inner conductor
c. inside the outer conductor
D. in between the two conductors
12
544 A magnetic needle placed near a wire carrying alternating current does not show any deflection. 12
545 Currents ( I_{1} ) and ( I_{2} ) flow in the wires
shown in figure. The field is zero at
distance ( x ) to the right of ( O . ) Then
( x=left(frac{I_{1}}{I_{2}}right) a )
3. ( x=left(frac{I_{2}}{I_{1}}right) a )
( x_{x}=left(frac{I_{1}-I_{2}}{I_{1}+I_{2}}right) a )
( x=left(frac{I_{1}+I_{2}}{I_{1}-I_{2}}right) a )
12
546 Assertion: Magnetic force between two short magnets, when they are co-axial follows inverse square law of distance. Reason : The magnetic forces between two poles do not follow inverse square
law of distance
A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true and reason is not the correct explanation of assertion.
c. If assertion is true but reason is false
D. If both assertion and reason are false
12
547 Two concentric coils of 10 turns each
are placed in the same plane. Their radii are ( 20 mathrm{cm} ) and ( 40 mathrm{cm} ) and carry ( 0.2 mathrm{A} ) and 0.3 A current respectively in opposite directions. The magnetic induction (in tesla) at the centre is :
A ( cdot frac{3}{4} mu_{0} )
в. ( frac{5}{4} mu_{0} )
c. ( frac{7}{4} mu_{0} )
D. ( frac{9}{4} mu_{0} )
12
548 If long hollow copper pipe carries a direct current, the magnetic field associated with the current will be:
A. only inside the pipe
B. only outside the pipe
c. neither inside nor outside the pipe
D. both inside and outside the pipe
12
549 Under what condition the force acting
on charge particle moving in the
magnetic field minimum?
A. If it is either moving parallel to the magnetic field intensity.
B. If it is either moving antiparallel to the magnetic field intensity.
C. Charge particle moves perpendicular to the velocity vector.
D. Both A and B
12
550 A coil carrying current ( l ) has radius and number of units ( n ). It is rewound so that radius of new coil is ( frac{r}{4} ) and it
carries current ( l . ) The ratio of magnetic moment of new coil to that of original
coil is
A .
B. ( frac{1}{2} )
( c cdot frac{1}{4} )
D. 8
12
551 A beam of protons enters a uniform
magnetic field of ( 0.3 T ) with a velocity of
( 4 times 10^{5} mathrm{m} / mathrm{s} ) in a direction making an
angle of ( 60^{circ} ) with the direction of
magnetic field. The path of motion of the particle will be :
A . circular
B. straight line
c. parabolic
D. helical
12
552 A toroid has a core(non-ferromagnetic) of inner radius ( 25 mathrm{cm} ) and outer radius
( 26 mathrm{cm}, ) around which 3500 turns of a
wire are wound. If the current in the wire
is ( 11 A ), the magnetic field inside the core of the toroid is?
12
553 A proton and an ( alpha- ) particle (with their
masses in the ratio of 1: 4 and charges
in the ratio of 1: 2 ) are accelerated
from rest through a potential difference
V. If a uniform magnetic field (B) is set up perpendicular to their velocities, the
ratio of the radii ( r_{p}: r_{alpha} ) of the circular
path described by them will be :
A. ( 1: sqrt{2} )
Th ( : sqrt{2} cdot sqrt{2} )
B. 1: 2
( c cdot 1: 3 )
D. ( 1: sqrt{3} )
12
554 An electron beam projected along positive ( x ) -axis deflects along the positive y-axis.lf this deflection is caused by a magnetic field,what is the direction of the field? 12
555 9. In a region, steady and uniform electric and magnetic
fields are present. These fields are parallel to each other.
A charged particle is released from rest in this region. The
path of the particle will be
(a) an ellipse
(b) a circle
(c) a helix
(d) a straight line
(AIEEE 2006)
12
556 A current passing through a circle coil of two turns produces a magnetic field ( B ) as its centre. The coil is then rewound
so as to have four turns and the same
current is passed through it. The magnetic field at its centre now is
A ( .2 B )
B. ( B / 2 )
( c cdot B / 4 )
D. ( 4 B )
12
557 A charge ‘q’ moves in a region where electric field and magnetic field both exist, then force on it is : –
( mathbf{A} cdot q(vec{V} times vec{B}) )
B ( cdot q vec{E}+q(vec{V} times vec{B}) )
( mathbf{c} cdot q vec{E}+q(vec{B} times vec{V}) )
( mathbf{D} cdot q vec{B}+q(vec{E} times vec{V}) )
12
558 What we call the conductivity of a magnetic substance for the lines of
force with respect to air?
A. Magnetic induction
B. Magnetic permeability
c. Magnetic flux density
D. Intensity of magnetization
12
559 A force vector is acting on a unit length
of a thin wire, carrying a current ( boldsymbol{I}= )
( 80 A, ) at a point ( O . ) Find the magnitude
and direction of the force vector, if the
wire is bent as shown in figure above, the distance between the long parallel
segments of the wire being equal to ( l= )
( mathbf{2 0} boldsymbol{c m} )
A. ( 1.3 N )
B. ( 0.26 N )
c. ( 2.6 N )
D. ( 0.013 N )
12
560 A square frame of side carries i produces a field ( B ) at its centre. The
same current is passed through a circular coil having the same perimeter as the square. The field at the centre of circular coil is ( mathrm{B} ) ‘. Find the ratio of ( left(mathrm{B}^{prime} / mathrm{B}right) ).
A. ( frac{pi^{2}}{3 sqrt{2}} )
В. ( frac{pi^{2}}{5 sqrt{2}} )
c. ( frac{pi^{2}}{7 sqrt{2}} )
D. ( frac{pi^{2}}{8 sqrt{2}} )
12
561 A power line lies along the east-west direction and carries a current of 10
ampere. The force per metre due to the
earth’s magnetic field of ( 10^{-4} ) tesla is:
( mathbf{A} cdot 10^{-5} mathbf{N} )
B. ( 10^{-4} ) N
( mathbf{c} cdot 10^{-3} mathbf{N} )
D. ( 10^{-2} ) N
12
562 Two streams of electrons are moving parallel to each other in the same direction. They
A. attract each other
B. repel each other
c. cancel the electric field of each other
D. cancel the magnetic field of each other
12
563 The direction of the force on a current
carrying conductor held perpendicular to an uniform magnetic field is given by:
A. Fleming’s right hand rule
B. Ampere’s swimming rule
c. Maxwell’s right hand cork screw rule
D. Fleming’s left hand rule
12
564 A galvanometer coil has a resistance of
( 50 Omega ) and the meter shows full scale
deflection for a current of ( 5 m A ). This
galvanometer is converted into
voltmeter of range ( 0-20 V ) by
connecting
A. ( 3950 Omega ) in series with galvanometer
B. ( 4050 Omega ) in series with galvanometer
c. ( 3950 Omega ) in parallel with galvanometer
D. ( 4050 Omega ) in parallel with galvanometer
12
565 The magnetic flux through the cross-
section of the toroidal solenoid is
A ( cdot frac{mu_{0} N i h}{2 pi} )
В. ( frac{mu_{0} N i h(b-a)}{2 pi r} )
c. ( frac{mu_{0} N i h}{2 pi} log _{e} frac{b}{a} )
D. ( frac{mu_{0} N^{2} i h}{2 pi} log _{e} frac{a}{b} )
12
566 A point charge is moving in a circle with constant speed. Consider the magnetic field produced by the charge at a fixed
point ( boldsymbol{P} ) (not at the center of circle) on
the axis of the circle.
A. it is constant in magnitude only
B. it is constant in direction only
c. it is constant both in direction and magnitude both
D. it is constant neither in magnitude nor in direction both
12
567 At what distance from a long straight
wire carrying a current of ( 12 A ) will the
magnetic field be equal to ( 3 times ) ( mathbf{1 0}^{-mathbf{5}} boldsymbol{W b} / boldsymbol{m}^{2} ? )
A. ( 8 times 10^{-2} mathrm{m} )
В. ( 12 times 10^{-2} mathrm{m} )
c. ( 18 times 10^{-2} mathrm{m} )
D. ( 24 times 10^{-2} mathrm{m} )
12
568 The ratio of magnetic field at centre of circular loop to the magnetic field at the centre of square loop, which are made by a constant length current carrying wire :
A ( cdot frac{pi^{2}}{16} )
в. ( frac{pi^{2}}{8 sqrt{2}} )
c. ( frac{pi^{2}}{4 sqrt{2}} )
D. ( frac{pi^{2}}{2 sqrt{2}} )
12
569 Sensitivity of a moving coil
galvanometer can be increased by
Fill in the blank.
A. decreasing number of turns in rectangular coil
B. decreasing magnetic induction of magnetic field
C. increasing area of rectangular coil
D. increasing twist constant of phosphor bronze fiber
12
570 A proton moves in the positive ( z- )
direction after being accelerated from
rest through a potential difference ( V )
The proton then passes through a region with a uniform electric field ( E ) in
the positive x-direction and a uniform
magnetic field ( B ) in the positive ( y- ) direction, but the proton’s trajectory is not affected. If the experiment were
repeated using a potential difference of
( 2 V, ) the proton would then be
A. deflected in positive ( x ) -direction
B. deflected in negative ( x ) -direction
c. deflected in positive ( y ) -direction
D. deflected in negative ( y ) -direction
12
571 A coil of radius ( mathrm{R} ) carries a current I.
Another concentric coil of radius ( boldsymbol{r}(boldsymbol{r}<<boldsymbol{R}) ) caries current ( frac{boldsymbol{I}}{2} . ) Initially
planes of the two coils are mutually perpendicular and both the coils are
free to rotate about common diameter.
They are released from rest from this
position. The masses of the coils are ( mathbf{M} )
and m respectively ( (boldsymbol{m}>K_{1} )
12
572 Prakash peddles a stationary bicycle, the pedals of which are attached to a
100 turn coil of area ( 0.1 m^{2} . ) The coil
rotates at half a revolution per second
and it is placed in a uniform magnetic field of ( 0.01 T ) perpendicular to the axis
of rotation of the coil. Determine the
maximum voltage generated in the coil.
12
573 Two charges of same magnitude move
in two circlesof radii ( boldsymbol{R}_{1}=boldsymbol{R} ) and ( boldsymbol{R}_{2}= )
( 2 R ) in a region of constant uniform
magnetic field ( B_{0} . ) The work ( W_{1}, ) and ( W_{2} )
done by the magnetic field in the Two cases, respectively are such that:
A ( . W_{1}=W_{2}=0 )
В. ( W_{1}>W_{2} )
c. ( W_{1}=W_{2} neq 0 )
D. ( W_{1}<W_{2} )
12
574 A particle of charge ( q ) and mass ( m ) is
moving at a speed ( v ) enters a uniform
magnetic field of strength ( B ) as shown
below.
How much work is done by the magnetic field on the charge as the field accelerates the charge into a circle
of radius ( r ? )
( r )
9
( A )
B.
( mathbf{c} cdot q v B r )
D. ( m v^{2} )
E. Cannot be determined
12
575 If there is a circular coil having n turns,
the field produced is
A. ( 1 / n ) times as that produced by single turn.
B. ( n ) times as large as that produced by a single turn.
C. ( 2 / n ) times as large as that produced by a single turn.
D. all
12
576 A uniform magnetic field ( vec{B}=B_{0} hat{j} )
exists in a space. A particle of mass ( m )
and charge q is projected towards
negative ( x ) -axis with speed ( v ) from the a
point ( (d, 0,0) . ) The maximum value v for
which the particle does not hit ( y ) -z plane is?
( mathbf{A} cdot frac{2 B q}{d m} )
B. ( frac{B q d}{m} )
( mathbf{c} cdot frac{B q}{2 d m} )
D. ( frac{B q d}{2 m} )
12
577 A uniform magnetic field of 1.5 T exists in a cylindrical region of radius ( 10.0 mathrm{cm} ) its direction parallel to the axis along east to west. A wire carrying current of ( 7.0 mathrm{A} ) in the north to south direction passes through this region. What is the magnitude and direction of the force on the wire if,(a) the wire intersects the axis,(b) the wire is turned from N-S to northeast-northwest direction,(c) the
wire in the N-S direction is lowered from
the axis by a distance of ( 6.0 mathrm{cm} ) ?
12
578 A large solenoid of windings of 400
turns per meter carries a current ( 5 mathrm{A} )
The magnetic field at the centre of the solenoid is about:
A . ( 1.2 mathrm{mT} )
B. zero
c. ( 5.0 mathrm{mT} )
D. 2.5 mT
12
579 A galvanometer of resistance ( 50 Omega ) giving full scale deflection for a current
of 10 milliampere is to be changed into a voltmeter of range ( 100 mathrm{V} )

A resistance of ( _{-1}-ldots_{text {has to be }} )
connected in series with the
galvanometer.
A . 9950
B. 10025
c. 10000
D. 9975

12
580 Magnetic field strength at the centre of
regular pentagon made of a conducting wire of uniform cross section area as
shown in figure is : (i amount of current
enters at A and leaves at E)
( mathbf{A} cdot frac{5 mu_{0} i}{4 pi a}left[2 sin frac{72^{0}}{2}right] )
( B . quad 0 )
C ( cdot frac{3 mu_{0} i}{4 pi}left[2 sin frac{72^{0}}{2}right] )
D. ( frac{mu_{0} i}{4 pi a}left[2 sin frac{72^{0}}{2}right] )
12
581 The equation of line on which magnetic
field is zero due to system of two
perpendicular infinitely long current
carrying straight wires, is
A. ( x=y )
B. ( x=2 y )
c. ( x=3 y )
D. ( 3 x=y )
12
582 A copper wire of diameter ( 1.6 m m )
carries a current ( i . ) The maximum
magnetic field due to this wire is ( 5 x )
( 10^{-3} T . ) The value of ( i ) is
A ( .40 A )
в. ( 5 A )
( c cdot 20 A )
D. 2A
12
583 Two conducting coils are placed coaxially now a cell is connected in one coil then they will :-
A. Attract to each other
B. Repel to each other
( c . ) Both (1)( &(2) )
D. They will not experience any force
12
584 A wire along ( x- ) axis carries a current
( 3.5 A . ) Find the force on a ( 1 mathrm{m} ) section of the wire exerted by ( vec{B}=(0.74 hat{j}- ) ( mathbf{0} . mathbf{3 6} hat{boldsymbol{k}}) boldsymbol{T} .(text { in } mathbf{N}): )
A. ( 2.59 hat{k}+1.263 )
3
в. ( 1.26 hat{k}-2.59 hat{jmath} )
c. ( -2.59 hat{k}-1.26 hat{j} )
D . ( -1.26 hat{k}+2.59 hat{j} )
12
585 A beam of protons with a velocity ( 4 times ) ( 10^{5} m s^{-1} ) enters a uniform magnetic
field of ( 0.3 mathrm{T} ) at an angle of ( 60^{circ} ) to the
magnetic field. Find the pitch of the helix (which is the distance travelled by a proton in the beam parallel to the magnetic field during one period of the rotation). Mass of the proton ( =1.67 times )
( mathbf{1 0}^{-2 mathbf{7}} mathbf{k g} )
( A cdot 2.3 mathrm{cm} )
B. 5.35 ( mathrm{cm} )
( c cdot 4.35 mathrm{cm} )
D. 6.35 ( mathrm{cm} )
12
586 A circular coil of 16 turns and radius 10
( mathrm{cm} ) carrying a current of ( 0.75 mathrm{A} ) rests
with its plane normal to an external
field of magnitude ( 5.0 times 10^{-2} ) T. The coil
is free to turn about an axis in its plane perpendicular to the filed direction. When the coil is turned slightly and released, it oscillates about its stable
equilibrium with a frequency of ( 2.0 / s ) What is the moment of inertia of the
coil about its axis of rotation?
A ( .1 .2 times 10^{4} g-c m^{2} )
B. ( 3 times 10^{4} k g-m^{2} )
c. ( 0.3 times 10^{4} k g-m^{2} )
D. ( 1.2 times 10^{4} k g-m^{2} )
12
587 The shunt required to send ( 10 % ) of the main current through a moving coil galvanometer of resistance ( 99 Omega ) is
( mathbf{A} cdot 99 Omega )
в. ( 9.9 Omega )
c. ( 9 Omega )
D. ( 10 Omega )
E . ( 11 Omega )
12
588 For a positively charged particle moving
in a ( x ) -y plane initially along the ( x ) -axis, there is a sudden change in its path due to the presence of electric and/or magnetic fields beyond P. The curved path is shown in the ( x ) -y plane and is found to be non-circular.Which one of
the following combinations is possible?
A ( cdot vec{E}=0, vec{B}=b hat{i}+c hat{k} )
в. ( vec{E}=a hat{i}, vec{B}=c hat{k}+a hat{i} )
c. ( vec{E}=0, vec{B}=c hat{j}+b hat{k} )
D. ( vec{E}=a hat{i}, vec{B}=c hat{k}+b hat{j} )
12
589 Magnetic field due to a toroid inside its
turns is given by ( ( n ) is thenumber of
turns per unit length of the toroid and ( boldsymbol{I} ) is the current in the loop)
( mathbf{A} cdot B=mu_{o} n I )
В. ( B=epsilon_{o} n I )
( mathbf{c} cdot B=frac{mu_{o}}{4 pi} n I )
D. None of these
12
590 A circular current carrying coil has a radius ( R ). The distance from the centre
of the coil on the axis where the
magnetic induction will be ( left(frac{1}{8}right)^{t h} ) of its value at the centre of the coil is
A ( cdot frac{R}{sqrt{3}} )
в. ( R sqrt{3} )
с. ( 2 R sqrt{3} )

D. ( left(frac{2}{sqrt{3}}right)^{R} )
12
591 If the current in a wire is directed east
wards and it is kept in a magnetic field directed northwards, the direction of
force on the wire is:
A. due west
B. due south
c. vertically upwards
D. vertically downwards
12
592 Calculate force per unit length acting
on the wire B due to the current flowing
in the wire ( A )
12
593 Two thin, long,parallel wires,seperated by a distance ‘d’ carry a current of ‘i’A in the same direction.They will:
A. Attract each other
B. Repel,each other
c. Depend upon the material of wire
D. Can’t say
12
594 A conducting circular loop made of a thin wire, has area ( 3.5 times 10^{-3} m^{2} ) and
resistance ( 10 Omega ). It is placed perpendicular to a time dependent magnetic field ( B(t)=(0.4 T) sin (50 pi t) )
The field is uniform in space. Then the net charge flowing through the loop during ( t=0 s ) and ( t=10 m s ) is close to:
A. ( 0.14 m C )
В. ( 0.21 mathrm{mC} )
( c cdot 6 m C )
D. ( 7 m C )
12
595 How can you verify that a current carrying wire produces a magnetic field with the help of an experiment? 12
596 A long solenoid carrying a current
produces a magnetic field B along its axis. If the current is doubled and the
number of turns per cm is halved, the new value of the magnetic field is
( A cdot B / 2 )
B. B
( c cdot 2 B )
D. 4 B
12
597 A proton is projected horizontally eastward in a uniform magnetic field, which is horizontal and southward in
direction. The proton will be deflected
A. upwarddardpwardd
B. downward
c. northward
D. southward
12
598 A current I flows in the anticlockwise
direction through a square loop of side a lying in the xoy plane with its center at the origin. The magnetic induction at the center of the square loop is
A ( cdot frac{2 sqrt{2} mu_{0} I}{pi a} hat{e}_{x} )
B. ( frac{2 sqrt{2} mu_{0} I}{pi a} hat{e}_{z} )
( ^{mathrm{c}} cdot frac{2 sqrt{2} mu_{0} I}{pi a^{2}} hat{e}_{z} )
D. ( frac{2 sqrt{2} mu_{0} I}{pi a^{2}} hat{e}_{x} )
12
599 Which of the following changes would cause the pointer to deflect through a larger angle?
A. Move the magnet faster
B. Move the magnet away from the solenoid
c. Unwind some of the turns of the solenoid
D. Keep the magnet stationary
12
600 A wire in the form of a circular loop of one turn carrying a current produces a magnetic field ( B ) at the centre. If the
same wire is looped into a coil of two turns and carries the same current, the
new value of magnetic induction at the
centre is:
( A .3 B )
в. ( 5 B )
( c .4 B )
D. 2 ( B )
12
601 Complete the following sentence A current carrying solenoid behaves like
( a )
A. bar magnet
B. resistance
c. inductance
D. none of these
12
602 toppr )
Q Type your question
the rigure. the alstance ( boldsymbol{a} ) Is ( mathbf{U} . mathbf{I} boldsymbol{Z} mathbf{U} boldsymbol{m} )
When the two charges are at the
locations as shown in the figure, what
are the magnitude and direction of the
net magnetic field they produce at point
( boldsymbol{P ?} )
(Take ( boldsymbol{v}=mathbf{4 . 5 0} times mathbf{1 0}^{mathbf{6}} mathbf{m} boldsymbol{s}^{-1} ) and ( boldsymbol{v}^{prime}= )
( left.9.00 times 10^{6} m s^{-1}right) )
A ( .4 .38 times 10^{-4} T, ) into the page
B. ( 4.38 times 10^{-4} T ), out of the page
( c: quad 10^{-4} T, ) into the page
D. ( 2.9 times 10^{-9} T, ) out of the page
12
603 A uniform electric field and uniform
magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron
A. will turn towards right of direction of motion
B. speed will decrease
c. speed will increase
D. will turn towards left direction of motion
12
604 A current of one ampere is passed
through a straight wire of length 2 metre. The magnetic field at a point in
air at a distance of ( 3 mathrm{m} ) from one end of
the wire but lying on the axis of the wire will be:
A ( cdot mu_{0} / 2 pi )
B . ( mu_{0} / 4 pi )
c. ( mu_{0} / 8 pi )
D. zero
12
605 In the following diagram an arrow
shows the motion of the coil towards the
bar magnet.
(i) State in which direction the current
flows: ( A ) to ( B ) or ( B ) to ( A ) ?
(ii) Name the law used to come to the
conclusion.
12
606 When a current carrying coil is placed in a uniform magnetic field of induction
( B, ) then a torque ( tau ) acts on it. If ( I ) is the current, ( n ) is the number of turns and ( A )
is the face area of the coil and the
normal to the coil makes an angle ( theta )
with ( boldsymbol{B}, ) Then
A ( cdot tau=B I n A )
B. ( tau=B ) In ( A sin theta )
( mathbf{c} cdot tau=B operatorname{In} A cos theta )
( mathbf{D} cdot tau=B I n A tan theta )
12
607 Consider two thin identical conducting wires covered with very thin insulating material. One of the wires is bent into a
loop and produces magnetic field ( B_{1} ) at
its centre when a current ( I ) passes
through it. The second wire is bent into
a coil with free identical loops adjacent to each other and produces magnetic
field ( B_{2} ) at the centre of loops with
current ( I / 3 ) passing through it. The
ratio ( boldsymbol{B}_{1}: boldsymbol{B}_{2} )
A. 1: 1
B. 1: 3
c. 1: 9
D. 9: 1
12
608 A long copper wire is wound in the form
of a coil of radius ( r . ) A current of ( 2 A ) is
passed through this coil and the magnetic induction at the centre of this coil is noted. The same wire is now
folded end to end and coil of the same
radius ( r ) is prepared and the same current is passed through it. The magnetic induction at the centre
A. Will be doubled
B. Will be halved
c. will remain same
D. Will drop to zero
12
609 Which of the following material is used in making the core of a moving coil galvanometer?
A. copper
B. Nickel
c. Iron
D. Both (a) and (b)
12
610 Explain Fleming’s left hand rule with the help of labelled diagram. 12
611 The self-inductance of an air core
solenoid of 100 turns is 1 m ( H ). The self-
inductance of another Solenoid of 50
turns (with the same length and crosssectional area) with a core having relative permeability 500 is
A . ( 125 mathrm{mH} )
B. 24 mH
c. ( 60 mathrm{mH} )
D. 30 mH
E. ( 45 mathrm{mH} )
12
612 The diagram below shows a positively charged particle moving toward the right and about to enter a magnetic field whose direction is shown by the blue arrows. What is the direction of the
force on the positively charged particle (from our point of view) at the instant it
enters the magnetic field?
A . right
B. left
c. up
D. toward us
E. away from us
12
613 A deuteron of kinetic energy 50 keV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to the
magnetic field ( B ). The kinetic energy of the proton that describes a circular
orbit of radius 0.5 metre in the same
plane with the same ( B ) is
A . ( 25 ~ k e V )
В. ( 50 mathrm{keV} )
c. ( 200 mathrm{keV} )
D. ( 100 mathrm{keV} )
12
614 When does a moving charged particle
not experience any force while moving through a uniform magnetic field?
12
615 A circular current carrying coil has a radius ( R ). The distance from the centre
of the coil on the axis where the magnetic induction will be ( frac{1}{8} ) to its value at the centre of the coil, is :
A ( cdot frac{R}{sqrt{3}} )
в. ( R sqrt{3} )
c. ( 2 sqrt{3} R )
D. ( frac{2}{sqrt{3}} R )
12
616 If expressions for the magnetic field at a point due to a current element, in
C.G.S.system is given by ( overrightarrow{d B}=frac{mu_{0}}{4 pi} frac{i(d overrightarrow{d times vec{r}})}{a * r^{3}} )
Find a.
12
617 The path of a charged particle moving in
a magnetic field can be a :
This question has multiple correct options
A. Straight line
B. Circle
c. Parabola
D. Helix
12
618 Assertion
The magnetic field at the ends of a very long current carrying solenoid is half of that at the centre.
Reason
If the solenoid is sufficiently long, the field within it is uniform.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
619 Which one of the following are used to express the intensity of magnetic field in vacuum?
A . oersted
B. tesla
c. gauss
D. none of these
12
620 (a) Explain giving reasons, the basic difference in converting a galvanometer into
(i) a voltmeter and (ii) an ammeter
(b) Two long straight parallel
conductors carrying steady currents ( I_{1} )
and ( I_{2} ) are separated by a distance ( ^{prime} d^{prime} ) Explain briefly, with the help of a suitable diagram, how the magnetic field due to one conductor acts on the
other. Hence deduce the expression for
the force acting between the two conductors. Mention the nature of this
force.
12
621 Two long thin charged rods with charge density ( lambda ) each are placed parallel to each other at a distance d apart. The
force per unit length exerted on one rod by the other will bewhere ( left(boldsymbol{K}=frac{mathbf{1}}{mathbf{4} boldsymbol{pi} varepsilon_{0}}right) )
A ( cdot frac{K 2 lambda}{d} )
в. ( frac{K 2 lambda^{2}}{d} )
c. ( frac{K 2 lambda}{d^{2}} )
D. ( frac{K 2 lambda^{2}}{d^{2}} )
12
622 A current-carrying conductor when placed in a magnetic field always experiences a force. Is the given statement true or false? 12
623 A rectangular loop carrying current lis located near an infinite long straight
conductor carrying current l as shown
in the figure. The loop,
A. remain stationary
B. is attracted towards the wire
C. is repelled away from the wire
D. will rotate about an axis parallel to the wire
12
624 A beam of protons is moving horizontally towards you. As it approaches you, it passes through a magnetic field which is directed upwards. As you see it, the magnetic field will deflect the beam to the:
A. Right
B. Left
c. Top
D. Bottom
12
625 In a crossed field, the magnetic field
induction is ( 2.0 T ) and electric field
intensity is ( 20 times 10^{3} V / m . ) At which
velocity the electron will travel in a straight line without the effect of electric and magnetic fields?
A ( cdot frac{20}{16} times 10^{3} mathrm{ms}^{-1} )
B. ( 10 times 10^{3} mathrm{ms}^{-1} )
c. ( 20 times 10^{3} mathrm{ms}^{-1} )
D. ( 40 times 10^{3} mathrm{ms}^{-} )
12
626 In cyclotron the gyro radius is:
A. proportional to momentum
B. proportional to energy
C. inversely proportional to momentum
D. inversely proportional to energy
12
627 Two parallel beams of positrons moving
in the same direction will
A. Repel each other
B. Will not interact with each other
c. Attract each other
D. Be deflected normal to the plane containing the two beams
12
628 (a) Write Fleming’s left-hand rule for the direction of force on a current carrying conductor placed in a magnetic field.
(b) Draw a diagram to show lines of magnetic field inside and around a current carrying solenoid.
(c) Write the names of four devices
where current carrying conductor is used along with magnetic fields
12
629 If a charged particle is projected perpendicular to a uniform magnetic field, then
a) it revolves in circular path
b) its K.E. remains constant
c) its momentum remains constant
d) its path is spiral
A. only a, bare correct
B. only a, c are correctt
c. only b, dare correct
D. only a, dare correctt
12
630 A proton goes undeflected in a crossed electric and magnetic field (the fields
are perpendicular to each other) at a speed of ( 10^{5} mathrm{m} / mathrm{s} ). The velocity is
perpendicular to both the fields. When
the electric field is switched off, the
proton moves along a circle of radius 2
( mathrm{cm} . ) Find the magnitude of the electric and the magnetic fields. Take the mass of the proton ( =1.6 times 10^{-27} mathrm{kg} )
12
631 A charge particle of charge ( q, ) mass ( m ) is projected with a velocity ( vec{v}=v hat{i} ). The electric field ( overrightarrow{boldsymbol{E}}=boldsymbol{E} hat{boldsymbol{k}} ) and magnetic
field ( vec{B}=B hat{j} ) is applied. The
acceleration of the particle is then
A ( frac{q v B}{m} )
в. ( frac{q E}{m} )
c. ( frac{q(E+v B) hat{k}}{m} )
( D )
12
632 Establish the formula for intensity of magnetic field at the centre of a current carrying circular coil. 12
633 A current loop consists of two identical
semicircular parts each of radius ( mathrm{R} ), one
lying in the ( x ) -y plane and the other in ( x-z )
plane. If the current in the loop is i. The
resultant magnetic field due to the two
semicircular parts at their common
centre is
A ( cdot frac{mu_{0} i}{2 sqrt{2} R} )
B. ( frac{mu_{0} i}{2 R} )
c. ( frac{mu_{0} i}{4 R} )
D. ( frac{mu_{0} i}{sqrt{2} R} )
12
634 A current ( I=5.0 A ) flows along a thin
wire shaped as shown in figure above. The radius of a curved part of the wire is equal to ( R=120 m m ), the angle
( 2 varphi=90^{circ} . ) Find the magnetic induction
of the field at the point ( O ) in ( mu T . ) If the
answer is ( X ) then enter ( frac{X}{7} )
12
635 ( mathbf{1} )
( boldsymbol{m} ) long wire is folded in the form of a
circular coil and 100 m ( A ) electric
current is flowing in it, then magnetic
field at a point ( 1 ~ m ) away from its centre
on its axis :
( ^{text {A }} cdot frac{10^{-5}}{4 pi} T )
в. ( frac{10^{-8}}{2 pi} T )
( ^{text {c. }} cdot frac{10^{-5}}{2 pi} T )
D. ( frac{10^{-8}}{4 pi} T )
12
636 Write the dimensions of ( boldsymbol{E} / boldsymbol{B} ). Here ( , boldsymbol{E} ) is
the electric field and ( B ) is the magnetic field.
12
637 What do you mean by a solenoid? 12
638 A beam of electrons moving with a uniform speed of ( 4 times 10^{7} m s^{-1} ) is
projected normal to the uniform magnetic field where ( boldsymbol{B}=mathbf{1 0}^{-3} boldsymbol{W} boldsymbol{b} / boldsymbol{m}^{2} )
What is path of the beam in magnetic field?
12
639 A moving charge will produce
A. no field
B. a magnetic field.
c. a small electric field.
D. None of these
12
640 A uniform electric field and a uniform
magnetic field are produced, and are pointed in the same direction. An
electron is projected with its velocity pointed in the same direction
A. The electron will turn to its left
B. The electron velocity will decrease in magnitude
c. The electron will turn to its right
D. The electron velocity will increase in magnitude
12
641 A circular coil connected to a cell of
e.m.f ( boldsymbol{E} ) produced a magnetic field. The
coil is unwound, stretched to double its length, rewound into a coil of ( frac{1}{3} ) of the original radius and connected to a cell
of e.m.f ( boldsymbol{E}_{1} ) to produce the same field at
the centre. Then ( boldsymbol{E}_{mathbf{1}} ) is :
( mathbf{A} cdot frac{E}{2} )
B. ( frac{2 E}{3} )
c. ( frac{9 E}{4} )
D. ( frac{E}{6} )
12
642 A very long straight wire carries a
current I. At the instant when a charge ( +Q ) at point ( P ) has velocity ( vec{V}, ) as shown, the force on the charge is
A. Along ox
B. Opposite to oy
c. Along oy
D. Opposite to ox
12
643 A charged particle moves in a gravityfree space without change in velocity. Which of the following is/are possible? This question has multiple correct options
A. ( E=0, B=0 )
0
B. ( E=0, B neq 0 )
c. ( E neq 0, B=0 )
D. ( E neq 0, B neq 0 )
12
644 The correct expression for Ampere’s law
is :
A ( . int B . d l=Sigma i )
в. ( int B . d l=frac{1}{sum i} )
c. ( int B . d l=mu_{0} sum i )
‘ – ( int B . d l=frac{sum i}{mu_{0}} )
12
645 Find the magnitude of force acting on
the conductor carrying current ( boldsymbol{I} ) as
shown in the diagram. The magnitude of
magnetic field is ( B ) and direction is into
the plane of paper:
( mathbf{A} cdot I(2 L+mu R) B )
( mathbf{B} cdot I(2 L+R) B )
( mathbf{c} cdot I(2 L+2 R) B )
D. none of these
12
646 The length of conductor ab carrying
current ( I_{2} ) is ( l . ) The force acting on it due
to a long current carrying conductor as shown in figure. The midpoint of wire ab is distance ( x ) apart from long wire. The magnitude of the force on the wire is:
A ( cdot frac{mu_{0} I}{2 pi} log _{e} frac{x+l / 2}{x-l / 2} )
В. ( frac{mu_{0} I}{2 pi x} )
c. ( frac{mu_{0} I}{2 pi} log _{e} frac{x-l / 2}{x+l / 2} )
D. ( _{mu_{0} text { Ilog }_{e}} frac{x-l / 2}{x+l / 2} )
12
647 The magnetic field at center ( O ) of the
( operatorname{arcin} ) figure is
A ( cdot frac{mu_{0} I}{4 pi times r}[sqrt{2}+pi] )
( ^{mathbf{B}} cdot frac{mu I}{2 pi r}left[frac{pi}{4}+(sqrt{2}-1)right] )
C ( frac{mu_{0}}{4 pi} times frac{I}{r}[(sqrt{2}-pi)] )
( ^{mathrm{D}} cdot frac{mu_{0}}{4 pi} times frac{I}{r}left[left(sqrt{2}+frac{pi}{4}right)right] )
12
648 An electron is moving towards east in a magnetic field acting vertically downwards. So the electron is deflected
towards:
A. South
B. North
c. East
D. west
12
649 The figure showing Fleming’s left hand
rule is given. Which figure or thumb
shows the direction of flow of electric
current?
A. First finger
B. Second finger
c. Thumb
D. Small finger
12
650 Identify the wrong statement.
A. Current loop is equivalent to a magnetic dipole
B. Magnetic dipole moment of a planar loop of area ( A ) carrying current ( l ) is ( l^{2} A )
C. Particles like proton, electron carry an intrinsic magnetic moment
D. The current loop (magnetic moment ( m ) ) placed in a uniform magnetic field, ( B ) experiences a torque ( tau= ) ( m times B )
E. Ampere’s circuit law is not independent of Biot Savart’s law
12
651 In the given loop the magnetic field at
the centre 0 is :
A ( cdot frac{mu_{0} I}{4}left(frac{r_{1}+r_{2}}{r_{1} r_{2}}right) ) out of the page
B. ( frac{mu_{0} I}{4}left(frac{r_{1}+r_{2}}{r_{1} r_{2}}right) ) into the page
c. ( frac{mu_{0} I}{4}left(frac{r_{1}-r_{2}}{r_{1} r_{2}}right) ) out of the page
D. ( frac{mu_{0} I}{4}left(frac{r_{1}-r_{2}}{r_{1} r_{2}}right) ) into the page
12
652 Name any one instrument which works
on the principle of tangent law in magnetism
12
653 Two protons are moving with same velocity in magnetic field of same magnitude, then :
A. magnetic force on protons may be zero
B. magnetic force on both must be same to each other
c. magnetic force on both may or may not be same to each other
D. both ( (a) ) and ( (c) ) are correct
12
654 A square loop ( A B C D ) carrying a
current ( i, ) is placed near and coplanar
with a long straight conductor ( boldsymbol{X} boldsymbol{Y} )
carrying a current ( I, ) the net force on the
loop will be:
A ( cdot frac{2 mu_{0} I i}{3 pi} )
B. ( frac{mu_{0} I i}{2 pi} )
c. ( frac{2 mu_{0} text { Ii } L}{3 pi} )
D. ( frac{mu_{0} I i L}{2 pi} )
12
655 Derive an expression for the magnetic induction at a point on the axis of a current carrying circular coil using Biot-Savart law. 12
656 An ( alpha ) -particle and proton are
accelerated from rest through same potential difference and both enter into a uniform perpendicular magnetic field. Find the ratio of their radii of curvature.
A. ( sqrt{7}: 1 )
B. ( sqrt{5}: 1 )
c. ( sqrt{2}: 1 )
D. ( sqrt{3}: 1 )
12
657 A straight conductor carries a current. Assume that all free electrons in the
conductor move with the same drift velocity v. A and B are two observers on
a straight line XY parallel to the conductor. A is stationary. B moves along XY with a velocity v in the direction of the free electrons.
A. A and B observe the same magnetic field
B. A observes a magnetic field, B does not
c. A and B observe magnetic fields of the same magnitude but opposite directions
D. A and B do not observe any electric field
12
658 Electric field and magnetic field in a region of space is given by ( vec{E}=E_{o} hat{j} ) and
( vec{B}=B_{o} hat{j} cdot A ) particle of specific charge ( alpha )
is released from origin with velocity ( vec{v}=v_{o} hat{i} ).Then path of particle.
Note- ( boldsymbol{E}_{boldsymbol{o}}, boldsymbol{B}_{boldsymbol{o}} ) and ( boldsymbol{v}_{boldsymbol{o}} ) are constant values
( A ). is a circle
B. is a helix with uniform pitch
c. is a helix with non-uniform pitch
D. is cycloid
12
659 You are sitting in a room in which a strong magnetic field is directed from your left towards right. A beam of electrons is directed from front towards
you. What would be the direction of
magnetic force on this beam?
A. downwards
B. upwards.
c. towards right
D. towards left
12
660 Three long, straight and parallel wires are arranged as shown in figure. The
force experienced by ( 10 mathrm{cm} ) length of
wire ( boldsymbol{Q} ) is
A ( .1 .4 times 10^{-4} N ) toward the right
B. ( 1.4 times 10^{-4} N ) toward the left
c. ( 2.6 times 10^{-4} N ) toward the right
D. ( 2.6 times 10^{-4} N ) toward the left
12
661 An electron enters a uniform magnetic
field with a path perpendicular to the field lines and moves in a circular path
of radius ( boldsymbol{R} )

A positron (same mass of an electron
but opposite charge) enters the same magnetic field in a path perpendicular to the field with four times the kinetic
energy. Compared to the electrons path, the
radius of the protons circular path is:
A. The same radius
B. Twice as large
c. ( 1 / 2 ) as large
D. 4 times larger

12
662 Fill in the blanks:
A current carrying solenoid when freely suspended, it always rests in direction.
A. north-south
B. vertical
c. east-west
D. a direction inclined to north-south
12
663 A long solenoid with 40 turns per ( mathrm{cm} )
carries a current of ( 1 A . ) The magnetic
energy stored per unit volume is
( boldsymbol{J} / boldsymbol{m}^{3} )
A . ( 3.2 pi )
B. ( 32 pi )
c. ( 1.6 pi )
D. ( 6.4 pi )
12
664 An iron rod is placed parallel to the magnetic field of intensity ( 2000 mathrm{A} / mathrm{m} ) The magnetic flux through the rod is ( 6 times 10^{-4} W b ) and its cross-sectional
area is ( 3 mathrm{cm}^{2} ). The magnetic permeability of the rod in ( frac{W b}{A-m} ) is:
A ( cdot 10^{-1} )
B. ( 10^{-2} )
( mathbf{c} cdot 10^{-3} )
D. ( 10^{-4} )
12
665 The most suitable material to be used
as the core of an electromagnet is
A. Iron
B. steel
c. copper
D. Aluminium
12
666 A positive charge is at rest in a uniform magnetic field directed to the right. What force does the positive charge feel, due to the magnetic field?
A. An upward force
B. A downward force
c. A force to the left
D. No force is felt.
12
667 A permanent magnet moving coil gives full scale deflection at ( 40 mathrm{mV} ) potential difference and 8 mA current. What will
be the required series resistance when it is used as voltmeter of range ( 0200 mathrm{V} ? )
A . 19556 ohm
B. 20163 ohm
( c cdot 23884 ) ohm
D. 24995 ohm
12
668 Maximum current that can pass
through galvanometer is ( 0.002 A ) and
resistance of galvonameter is ( boldsymbol{R}_{boldsymbol{g}}= ) ( 50 Omega ) find out shunt resistance to
convert in into ammeter of range ( 0.5 A )
A . ( 0.5 Omega )
B. ( 0.2 Omega )
( c .0 .7 Omega )
D. ( 0.9 Omega )
12
669 A thin rod is bent in the shape of a small circle of radius r. If the charge per unit
length of the rod is ( sigma, ) and if the circle is rotated about its axis at a rate of
rotations per second, the magnetic induction at a point on the axis at a
large distance y from the centre is?
A ( cdot mu_{0} pi r^{3} n frac{sigma}{y^{3}} )
В ( cdot 2 mu_{0} pi r^{3} n frac{sigma}{y^{3}} )
c. ( left(frac{mu_{0}}{4 pi}right) r^{3} n frac{sigma}{y^{3}} )
D ( cdotleft(frac{mu_{0}}{2 pi}right)^{r^{3}} n frac{sigma}{y^{3}} )
12
670 A permanent magnet has the shape of a sufficiently thin disc magnetized along
its axis. The radius of the disc is ( boldsymbol{R}= )
1.0 ( c m . ) Evaluate the magnitude of a
molecular current ( I^{prime} ) flowing along
the rim of the disc if the magnetic induction at the point on the axis of the disc, lying at a distance ( boldsymbol{x}=mathbf{1 0} boldsymbol{c m} )
from its centre, is equal to ( B=30 mu T )
12
671 The field ( B ) at the centre of a circular coil
of radius ( r ) is ( pi ) times that due to a long
straight wire at a distance ( r ) from it for
equal currents. The figure shows three cases. In all cases the circular part has
radius ( r ) and straight ones are infinitely
long. For same current, the field ( B ) at the centre ( P ) in cases 1,2,3 has the ratio:
( ^{mathbf{A}} cdotleft(-frac{pi}{2}right): frac{pi}{2}:left(frac{3 pi}{4}-frac{1}{2}right) )
B ( cdotleft(-frac{pi}{2}+1right):left(frac{pi}{2}+1right):left(frac{3 pi}{4}-frac{1}{2}right) )
( mathbf{C} cdot-frac{pi}{2}: frac{pi}{2}: frac{3 pi}{4} )
D ( cdotleft(-frac{pi}{2}-1right):left(frac{pi}{4}+frac{1}{4}right):left(frac{3 pi}{4}+frac{1}{2}right) )
12
672 the ( x y ) -plane along the lines ( x=pm R )
The wire located at ( x=+R ) carries a
constant current ( I_{1} ) and the wire located
at ( x=-R ) carries a constant current ( boldsymbol{I}_{2} )
A circular loop of radius ( boldsymbol{R} ) is
suspended with its centre at ( (0,0, sqrt{3} R) ) and in a plane parallel to the
( boldsymbol{x} boldsymbol{y} ) -plane. This loop carries a constant
current ( I ) in the clockwise direction as
seen from above the loop. The current in the wire is taken to be positive if it is in the ( +hat{boldsymbol{j}} ) direction. Which of the following statements regarding the magnetic field ( vec{B} ) is (are) true?
This question has multiple correct options
A ( cdot ) If ( I_{1}=I_{2} ), then ( vec{B} ) cannot be equal to zero at the origin
(0,0,0)
B. If ( I_{1}>0 ) and ( I_{2}<0 ), then ( vec{B} ) can be equal to zero at the origin (0,0,0)
C ( cdot ) If ( I_{1}0, ) then ( vec{B} ) can be equal to zero at the origin (0,0,0)
D. If ( I_{1}=I_{2} ), then the ( z ) -component of the magnetic field at the centre of the loop is ( left(-frac{mu_{0} I}{2 R}right) )
12
673 If a magnet is dropped along the axial line of a horizontally held copper ring, then the acceleration of the magnet
while it passing through the ring will
A. Less than that due to gravity
B. Equal to that due to gravity
c. More than that due to gravity
D. Depend on the size of the ring and magnet
12
674 Meena draws magnetic field lines of field close to the axis of a current
carrying circular loop. As she moves away from the centre of the circular loop she observes that the lines keep on diverging. How will you explain her observation:
12
675 In moving coil galvanometer, strong horses shoe magnet of concave shaped
pole pieces is used to?
A. Increase space for rotation of coil
B. Reduce weight of galvanometer
c. Protect magnetic field which is parallel to plane of coil at any position
D. Make magnetic induction weak at the cnetre
12
676 A particle of charge ( q ) and mass ( m )
moves in a circular orbit of radius ( r )
with angular speed ( omega . ) The ratio of the
magnitude of its magnetic moment to that of its angular momentum depends
on
A. ( omega ) and ( q )
B. ( omega, q ) and ( m )
c. ( q ) and ( m )
D. ( omega ) and ( m )
12
677 The AC voltage across a resistance can be measured using a
A. moving magnet galvanometer
B. moving coil galvanometer
c. hot wire voltmeter
D. potentiometer
12
678 Some equipotential surfaces of the
magnetic scalar potential are shown in
figure. Magnetic field at a point in the
region is:
A ( cdot 10^{-4} mathrm{T} )
B . ( 0.5 times 10^{-4} mathrm{T} )
c. ( 2 times 10^{-4} mathrm{T} )
D. None of these
12
679 A wire of length ( 44 mathrm{cm} ) is bent into a
circle and a current of ( 9.8 A ) is passed through it. The intensity of magnetic induction at the centre of the circle is
( mathbf{A} cdot 8.8 times 10^{-6} T )
B . ( 8.8 times 10^{-5} T )
c. ( 8.4 times 10^{-6} T )
D. ( 61.5 times 10^{-5} T )
12
680 Ampere rule is used to determine:
A. direction of current
B. direction of magnetic field
c. direction of motion of the conductor
D. magnitude of current
12
681 (AUDOD 00)
(U) 10
8. A magnetic needle is kept in a non-uniform magnetic
field. It experiences
(a) a force but not torque
(b) a force and a torque
(c) neither a force, nor a torque
(d) a torque but not force
(AIEEE 2005)
12
682 A proton moving with a velocity V is acted upon by electric field E and magnetic field B. The proton will move undeflected if
A. E is perpendicular to B
B. E is parallel to V and perpendicular to B
C. E is parallel to B and both are perpendicular to
D. E, V and B are mutually perpendicular and ( V=E / B )
12
683 If magnetic flux through area ( 20 m^{2} ) at
point ( P ) in magnetic field is 50 Weber
then magnetic induction at point ( boldsymbol{P} ) is :
A . ( 5 T )
в. ( 200 T )
c. ( 1000 T )
D. ( 2.5 T )
12
684 toppr
Q Type your question
with same speed. P is a point on a line
joining the beams, at a distance ( x ) from
any one beam. The magnetic field at P is
B. If ( mathrm{B} ) is plotted against ( mathrm{x} ), which of the
following best represents the resulting
curve ?
( A )
B.
( c )
( D )
12
685 An electron accelerated by a potential
difference ( V=1.0 k V ) moves in a
uniform magnetic field at an angle ( boldsymbol{alpha}= )
( 30^{circ} ) to the vector ( B ) whose modulus is
( B=29 ) mT.Find the pitch of the helical
trajectory of the electron.
( A cdot 1 m )
B. ( 1 mathrm{cm} )
( c cdot 2 m )
D. ( 2 mathrm{cm} )
12
686 A uniform field of ( 30 mathrm{mT} ) exists in the ( +x )
direction. A particle of charge +ve and
( operatorname{mass} 1.67 times 10^{-27} mathrm{kg} ) is projected
through the field in the ( +Y ) direction with
a speed of ( 4.8 times 10^{6} m / s )
(a) Find the force on the charged particle in magnitude and direction
(b) Find the force if the particle were negatively charged.
(c) Describe the nature of path followed by the particle in both the cases.
12
687 A bar magnet has coercivity ( 4 times )
( 10^{3} A m^{-1} . ) It is desired to demagnetize
it by inserting it inside a solenoid ( 12 mathrm{cm} ) long and has 60 turns. The current that
should be sent through the solenoid is:
( A cdot 8 A )
в. ( 10 A )
( c .12 A )
D. ( 14 A )
12
688 In an experiment to determine e/m using Thomson’s method, electrons from the cathode accelerate through a
potential difference of ( 1.5 mathrm{kV} ). The beam
coming out of the anode enters crossed
electric and magnetic field of strengths
( 2 times 10^{4} V / m ) and ( 8.6 times 10^{-4} T )
respectively, The value of e/m.of
electron will be
A ( cdot 1.6 times 10^{11} mathrm{C} / mathrm{kg} )
B . ( 1.7 times 10^{11} mathrm{C} / mathrm{kg} )
C ( .1 .8 times 10^{11} mathrm{C} / mathrm{kg} )
D. ( 1.9 times 10^{11} mathrm{C} / mathrm{kg} )
12
689 A proton moves at a speed ( boldsymbol{v}=mathbf{2} times )
( 10^{6} m / s ) in a region of constant
magnetic field of magnitude ( boldsymbol{B}= )
( 0.05 T . ) The direction of the proton when
it enters this field is ( theta=30^{circ} ) to the field.
When you look along the direction of the magnetic field, the path is a circle projected on a plane perpendicular to the magnetic field. How far will the
protons move along the direction of ( boldsymbol{B} )
when 2 projected circles have been completed?
12
690 There wires are situated at the same
distance. A current of ( 1 A, 2 A, 3 A ) flows
through these wires in the same
direction. What is ratio ( boldsymbol{F}_{1} / boldsymbol{F}_{2} ) where ( boldsymbol{F}_{1} )
is force on 1 and ( F_{2} ) on ( 2 ? )
A . ( 7 / 8 )
B.
c. ( 9 / 8 )
D. none of the above
12
691 toppr OGII
Q Type your question_
What is an
centered on point ( P )
The segments are connected by straight
wires as shown, and an unseen source
of EMF creates a constant
counterclockwise current in the wire.
What is the direction of the magnetic
field created at point ( P ) due to each wire
segment?
A. Both segments 1 and 2 create magnetic field that is into the page at point ( P )
B. Both segments 1 and 2 create magnetic field that is out of the page at point ( P )
c. Segment 1 creates magnetic field that is out of the page; Segment 2 creates magnetic field that is into the page at point P.
D. Segment 1 creates magnetic field that is into the page:
Segment 2 creates magnetic field that is out of the page at point P.
12
692 An electron and a proton travel with equal speeds and in the same direction,
at ( 90^{circ} ) to a uniform magnetic field. They experience forces which are initially
A. in opposite direction and differ by a factor of about 1840
B. in the same direction and differ by a factor of about 1840
c. equal in magnitude but in opposite directions
D. identical
12
693 A wire ( A B ) is carrying a steady current 12 A and is lying on the table. Another wire CD carrying 5 A is held directly above ( A B ) at a height of ( 1 mathrm{mm} ). Find the mass per unit length of the wire CD so that it remains suspended at its position when left free. Give the directions of the
current flowing in ( mathrm{CD} ) with respect to that in ( A B[text { Take the value of } g= )
( left.10 m s^{-2}right] )
12
694 A stream of electrons and protons are
directed towards a narrow slit in a
screen (see figure). The intervening region has a uniform electric field ( boldsymbol{E} )
(vertically downwards) and a uniform
magnetic field ( B ) (out of the plane of the
figure) as shown. Then:
This question has multiple correct options
A ( cdot ) electron and protons with speed ( frac{|E|}{|B|} ) will pass through
the slitt
B. protons with speed ( frac{|E|}{|B|} ) will pass through the slit.
electrons of the same speed will not
c. neither electrons nor protons will go through the slitt irrespective of their speed
D. electrons will always be deflected upwards irrespective of their speed
12
695 A charged particle (charge q) is moving in a circle of radius ( R ) with uniform
speed
A ( cdot frac{q v R}{2} )
B ( cdot q v R^{2} )
c. ( frac{q v R^{2}}{2} )
D. ( q v R )
12
696 Two parallel beams of positron moving
in the same direction will :
A. not interact with each other
B. repel each other
c. attract each other
D. be deflected normal to the plane containing the two beams
12
697 In a circuit for finding the resistance of a galvanometer by half deflection
method, a ( 6 V ) battery and a high resistance of ( 11 k Omega ) are used. The figure
of merit of the galvanometer ( 60 mu A / ) division. In the absence of shunt
resistance, the galvanometer produces a deflection of ( theta=9 ) divisions when
current flows in the circuit. The value of
the shunt resistance that can cause the
deflection of ( boldsymbol{theta} / 2, ) is closest to
A . ( 55 Omega )
B. ( 110 Omega )
c. ( 220 Omega )
D. ( 550 Omega )
12
698 The magnetic moment vectors ( mu_{s} ) and
( mu_{l} ) associated with the intrinsic spin angular momentum ( S ) and orbital angular momentum ( l, ) respectively, of an electron are predicted by quantum theory (and verified experimentally to a high accuracy) to be given by:
( boldsymbol{mu}_{s}=-(e / boldsymbol{m}) boldsymbol{S} )
( boldsymbol{mu}_{l}=-(e / 2 m) l )
Which of these relations is in
accordance with the result
expected classically? Outline the derivation of the classical result.
12
699 The force of repulsion between two parallel wires is ( f ) when each one of
them carries a certain current I. If the
current in each is doubled, the force
between them would be
A ( cdot 4 / f )
B. ( 4 f )
( c cdot 2 f )
( D )
12
700 The figure shows a point ( P ) on the axis of
a circular loop carrying current I.The
correct direction of magnetic field vector at ( P ) due to ( overrightarrow{d l} ) is represented by
( A )
B. 2
( c cdot 3 )
( D )
12
701 A closely wound solenoid ( 80 mathrm{cm} ) long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8
( mathrm{cm} . ) If the current carried is ( 8.0 mathrm{A} )
estimate the magnitude of B inside the solenoid near its centre.
12
702 A system consists of two parallel planes carrying currents producing a uniform magnetic field of induction ( boldsymbol{B} )
between the planes. Outside this space
there is no magnetic field. If the magnetic force acting per unit area of each plane is ( F_{1}=frac{B^{2}}{x mu_{0}} . ) Find ( x )
12
703 A long straight wire of circular crosssection is made of a non-magnetic material. The wire is of radius a.The
wire carries a current ( I ) which is
uniformly distributed over its cross-
section. The energy stored per unit length in the magnetic field contained within the wire is
( mathbf{A} cdot u=frac{mu_{0} I^{2}}{8 pi} )
B. ( U=frac{mu_{0} I^{2}}{16 pi} )
( ^{mathbf{C}} cdot U=frac{mu_{0} I^{2}}{4 pi} )
D. ( U=frac{mu_{0} I^{2}}{2 pi} )
12
704 Currents of ( 10 A, 2 A ) are passed through two parallel wires ( A ) and ( B ) respectively in opposite directions. If the wire A is infinitely long and the length of the wire B is ( 2 m, ) the force on the conductor ( B )
which is situated at ( 10 mathrm{cm} )
distance from A will be
( mathbf{A} cdot 8 times 10^{-5} N )
B . ( 5 times 10^{-5} N )
c. ( 8 pi times 10^{-7} N )
D. ( 4 pi times 10^{-7} N )
12
705 Pick correct statement(s):
This question has multiple correct options
A. Newton’s ( 3^{r d} ) law is applicable for all frames of reference and all systems
B. Presence of a conductor near another conductor
increases capacitance of system
c. Magnetic moment of a toroid is zero
D. In a perfectly inelastic collision two colliding objects will always stick together after collision
12
706 A charged particle (charge q) is moving in a circle of radius ( R ) with uniform
speed v. The associated magnetic
moment ( mu ) is given by
A ( cdot q v R )
в. ( _{q v} frac{R}{2} )
( mathbf{c} cdot q v R^{2} )
D. ( _{q v} frac{R^{2}}{2} )
12
707 A coil carrying a heavy current and having large number of turns is mounted in a N-S vertical plane. A current flows in the clockwise direction.
A small magnetic needle at its centre will have its north pole in
A. east-north direction
B. west-north direction
c. east-south direction
D. west-south direction
12
708 Magnetic field which keeps the
particles in circular path must
A. remain a constant everywhere
B. increase gradually with a rate proportional to kinetic energy of the particle
C. increase gradually with a rate proportional to speed of the particle
D. none of these
12
709 ( mathbf{A}-mathbf{4} . mathbf{8 0} mu mathbf{C} ) charge is moving at a
constant velocity of ( 6.80 times 10^{5} m / s ) in
the ( +x ) direction relative to a reference frame.At the instant when the point
charge is at the origin,what is the magnetic field vector it produces at the following points ( x=0, y=0.500 mathrm{m}, z=0 ? )
12
710 Figure shows a small loop carrying
current ( I . ) The curved portion is an arc of
a circle of radius ( R ) and the straight portion is a chord to the same circle subtending at an angle ( theta . ) The magnetic
induction at center ( O ) is :
A . zero
B. always inward irrespective of the value of ( theta )
c. inward as long as ( theta ) is less than ( pi )
D. always outward irrespective of the value of ( theta )
12
711 If the magnetizing field on a ferromagnetic material is increased, its
permeability.
A . Decreased
B. Increased
c. Is unaffected
D. May be increased or decreased
12
712 A current of ( 1 A ) flowing along positive ( x ) axis through a straight wire of length ( 0.5 m ) placed in a region of a magnetic field given by ( vec{B}=(2 hat{i}+4 hat{j}) ) T. The
magnitude and direction of the force experienced by the wire respectively
are:
A. ( sqrt{18} N, ) along positive ( z ) axis
B. ( sqrt{20} N ), along positive ( x ) axis
c. ( 2 N ) along positive z axis
D. ( 4 N ) along positive Y axis
12
713 A closed curve encircles several conductors.The line integral ( int overrightarrow{boldsymbol{B}} cdot boldsymbol{d} overrightarrow{boldsymbol{l}} )
around this curve is ( 3.83 times 10^{-7} T-m )
If you were to integrate around the curve in the opposite direction, what
could be the value of the line integral?
12
714 A beam of cathode rays is subjected to crossed.Electric (E) and Magnetic fields
(B). The fields are adjusted such that the beam is not deflected.The specific
charge of the cathode rays is given by –
(where ( V ) is the potential difference between cathode and anode)
A ( cdot frac{B^{2}}{2 V E^{2}} )
B. ( frac{2 V B^{2}}{E^{2}} )
( ^{mathbf{C}} cdot frac{2 V E^{2}}{B^{2}} )
D. ( frac{E^{2}}{2 V B^{2}} )
12
715 A particle carrying a charge equal to 100 times the charge on an electron is
rotating one rotation per second in a circular path of radius ( 0.8 mathrm{m} ). The value of the magnetic field produced at the centre will be:
( left(mu_{0}=text { permeability for vacuum }right) )
( ^{A} cdot frac{10^{-7}}{mu_{0}} )
B . ( 10^{-17} mu_{0} )
( mathbf{c} cdot 10^{-6} mu_{0} )
D. ( 10^{-7} mu_{0} )
12
716 A rectangular loop of sides ( 10 mathrm{cm} ) and 5
cm carrying a current I and 12 A is placed in different orientations as
shown in the figures above. If there is a uniform magnetic field of ( 0.3 mathrm{T} ) in the positive z direction, in which
orientations the loop would be in (i)
stable equilibrium and (ii) unstable equilibrium?
( A cdot(A) ) and
(B), respectively
B. (A) and
(C), respectively
( c cdot(B) ) and
(D), respectively
D. (B) and
(C), respectively
12
717 A portion of a conductive wire is bent in
the form of a semicircle of radius r as
shown below in figure. At the centre of semicircle, the magnetic induction will
be:
A. zero
B. inifinite
C ( cdot frac{mu_{0}}{4 pi} cdot frac{pi i}{2 r} ) tesla
D. ( frac{mu_{0}}{4 pi} cdot frac{pi i}{r} ) tesla
12
718 Two long, thin, parallel conductors, separated by a distance d carry
currents ( i_{1} ) and ( i_{2} . ) The force acting on unit length of any one conductor is ( mathrm{F} ) :
This question has multiple correct options
A . F is attractive, if ( i_{1} ) and ( i_{2} ) flow in the same directions
B. F is attractive, if ( i_{1} ) and ( i_{2} ) flow in the opposite directions
c. F is the same for both conductors
D. F is the different for the two conductors
12
719 If a galvanometer has full scale
deflection current ( I_{G} ) and resistance ( G )
A shunt resistance ( R_{A} ) is used to
convert it into an ammeter of range ( boldsymbol{I}_{mathbf{0}} )
and a resistance ( R_{V} ) is connected in series to convert it into a voltmeter of
range ( V_{0} ) such that ( V_{0}=I_{0} G ) then
( R_{A} R_{V} ) and ( frac{R_{A}}{R_{V}} ) respectively are
( ^{mathbf{A}} cdot G^{2} ) and ( frac{I_{G}^{2}}{left(I_{0}-I_{G}right)^{2}} )
в. ( G^{2} ) and ( frac{I_{0}^{2}}{left(I_{0}-I_{G}right)^{2}} )
( ^{mathrm{c}} cdot G^{2} ) and ( frac{I_{G}}{left(I_{0}-I_{G}right)^{2}} )
D. ( G^{2} ) and ( frac{I_{G}^{2}}{left(I_{0}+I_{G}right)^{2}} )
12
720 A circular coil of radius ( 25 mathrm{cm} ), carries a
current of ( 50 A ). If it has 35 turns, the
flux density at the centre of the coil is ( W b / m^{2} )
A ( cdot pi times 10^{-3} )
В. ( 1.4 pi times 10^{-3} )
c. ( 14 pi times 10^{-3} )
D ( .2 pi times 10^{-3} )
12
721 In an electric motor, wires carrying a
current of ( 5 A ) are placed at right angles to a magnetic field of induction 0.8 T. If
each wire has length of ( 20 mathrm{cm} ), then the
force acting on each wire is :
A ( .0 .2 N )
в. 0.4 N
( c cdot 0.6 N )
D. ( 0.8 N )
12
722 No net force acts on a rectangular coil
carrying a steady current when suspended freely in a uniform magnetic field.
A. True
B. False
12
723 Q Type your question
through the side, along the diameter of
a cross section of the coil. From out
point of view, we are looking straight through the coil.
We can see from the diagram that from
out perspective, the coil carries a clockwise conventional current, and the straight wire carries a conventional
current to the right. From our perspective, what is the
direction of the force on the segment of straight wire in the coil, due to the magnetic field produced by the coil?
A. Away from us
B. Toward us
( c cdot u p )
D. Down
E . Right
12
724 A circular coil of wire is connected to a battery of negligible internal resistance and has magnetic induction ( B ) at its centre. If the coil is unwound and
rewound to have double the number of
turns, and is connected to the same
battery, then the magnetic induction at
the center is :
( mathbf{A} cdot 2 B )
в. ( 4 B )
( c . B )
D. ( 0.5 B )
12
725 The oscillator frequency of a cyclotron is 10 MHz what should be the operating magnetic field accelerating proton?
A . 0.156 न
B. 0.256 T
c. 0.356 न
D. 0.656 T
12
726 A circular loop of area ( 1 mathrm{cm}^{2}, ) carrying a current of ( 10 mathrm{A}, ) is placed in a magnetic field of ( 0.1 mathrm{T} ) perpendicular to the plane of the loop. The torque on the loop due to the magnetic field is?
A. zero
B. ( 10^{-4} mathrm{N}-mathrm{m} )
( c cdot 10^{-2} N-m )
D. 1N-m
12
727 A vertical straight conductor carries a current vertically upwards. A point P lies to the east of it at a small distance and
another point ( Q ) lies to the west at the same distance the magnetic field at ( mathrm{P} )
is :
A. greater than at ( Q )
B. same as at ( Q )
c. less than at ( Q )
D. greater or less than at Q depending upon the strength of current
12
728 A coil of radius ( pi ) meters, 100 turns
carries a current of ( 3 A ). The magnetic induction at a point on its axis at a distance equal to ( sqrt{3} ) times its radius from its centre is :
A. ( 7.2 times 10^{-6} mathrm{Wbm}^{-2} )
в. ( 7.4 times 10^{-6} mathrm{Wbm}^{-2} )
c. ( 7.5 times 10^{-6} mathrm{Wbm}^{-2} )
D. ( 7.83 times 10^{-6} mathrm{Wbm}^{-2} )
12
729 The resistance of a galvanometer is ( 50 Omega ) and the current required to give full-scale deflection is ( 100 mu A ). In order
to convert it into an ammeter, reading upto ( 10 A, ) it is necessary to put
resistance of:
( mathbf{A} cdot 5 times 10^{-3} Omega ) in parallel
B. ( 5 times 10^{-4} Omega ) in parallel
( mathrm{c} cdot 10^{5} Omega ) in series
D. ( 99950 Omega ) in series
12
730 To send ( 10 % ) of the main current through a moving coil galvanometer of resistance 99 the shunt required is-
A . 1
B. 9
( c cdot 100 )
( D cdot 19 )
12
731 The magnetic field intensity due to a solenoid at end point ( boldsymbol{P} ) is :
A. ( mu_{0} n I )
в. ( frac{mu_{0} n I}{2} )
c. ( frac{mu_{0} n I}{2}(cos theta-cos phi) )
D. ( frac{mu_{0} n I}{2}(sin theta-sin phi) )
12
732 A solenoid with 600 turns per metre and
a radius of ( 2 mathrm{cm}, ) carries a time varying
current ( i(t)=left(6+4 t^{2}right) ) A. The electric
field at a distance ( 4 mathrm{cm} ) from the axis of
the solenoid at ( t=2 s ) will be ( (operatorname{in} mu vee mathrm{m} )
-1 to the nearest integer
4.48
3.60
( c .68 )
38
12
733 A proton takes ( 10^{-12} ) seconds to
complete one revolution in uniform
magnetic field. The time taken in another orbit of double the radius in
the same field is
B . ( 2 times 10^{-12} ) seconds
c. ( 4 times 10^{-12} ) seconds
D. ( 10^{-12} ) seconds
12
734 What is a solenoid? Compare the
magnetic field produced by a solenoid with the magnetic field of a bar magnet.
Draw neat figures and name various
components.
12
735 If the magnetic moment of the coil is ( 36 times 10^{-X} A m^{2} . ) Find ( X ? ) 12
736 Two identical circular wires ( P ) and ( Q )
each of radius ( boldsymbol{R} ) and carrying current
( I^{prime} ) are kept in perpendicular planes
such that they have a common centre
as shown in the figure. Find the
magnitude and direction of the net magnetic field at the common centre of
the two coils.
12
737 Two long straight parallel conductors
carry steady current ( boldsymbol{I}_{1} ) and ( boldsymbol{I}_{2} ) separated by a distance d. If the currents are flowing in the same direction, show how the magnetic field set up in one produces an attractive force on the other. Obtain the
expression for this force. Hence define
one ampere
12
738 There will be no force between two wires
carrying currents if currents are
A. parallel to each other
B. antiparallel to each other
C. perpendicular to each other
D. none of these.
12
739 What should be the magnitude and
direction of electric field?
A ( cdot 7 N c^{-1}, ) Vertically up ( perp ) to velocity
B. ( 7 N c^{-1} ), horizontally and ( perp ) to velocity
C . ( 14 N c^{-1} ), horizontally parallel to velocity
D. none of these
12
740 In the given diagram, a line of force of a particular force field is shown. Out of
the
following options, it can never
represent

This question has multiple correct options
A . an electrostatic field
B. a magnetostatic field
c. a gravitational field of a mass at rest
D. an induced electric field

12
741 The magnetic field of an electromagnetic wave is given by ( : vec{B}= )
( mathbf{1 . 6} times mathbf{1 0}^{-mathbf{6}} cos left(mathbf{2} times mathbf{1 0}^{mathbf{7}} boldsymbol{z}+mathbf{6} timesright. )
( left.10^{15} tright)(2 hat{i}+hat{j}) frac{W b}{m^{2}} ) The associated
electric field will be :-
A ( cdot vec{E}=4.8 times 10^{2} cos left(2 times 10^{7} z+6 times 10^{15} tright)(hat{i}-2 hat{j}) frac{V}{m} )
B ( cdot vec{E}=4.8 times 10^{2} cos left(2 times 10^{7} z-6 times 10^{15} tright)(2 hat{i}+hat{j}) frac{V}{m} )
C・ ( vec{E}=4.8 times 10^{2} cos left(2 times 10^{7} z-6 times 10^{15} tright)(-2 hat{j}+hat{i}) frac{V}{m} )
D・ ( vec{E}=4.8 times 10^{2} cos left(2 times 10^{7} z+6 times 10^{15} tright)(-hat{i}+2 hat{j}) frac{V}{m} )
12
742 A circular current carrying coil has a
radius r. Find the distance from the
centre of coil, on its axis, where the
magnetic induction will be ( 1 / 8 ) th of its
value at the centre of coil.
12
743 Magnetic moment of the spinning electron is in the direction of its spin
angular momentum.
B. Spin Velocity
c. spin angular velocity
D. angular acceleration
12
744 A pair of long, straight current-carrying
wires and four marked points are shown
in above figure. Find out the points at
which net magnetic field is zero?
A. Point 1 only
B. Points 1 and 2 only
c. Point 2 only
D. Points 3 and 4 only
E. Point 3 only
12
745 Define magnetization. Write its Sl unit and dimensions. 12
746 A closed iron ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling
magnet is:
A. equal to g
B. less thang
c. more than g
D. depends on the diameter of the ring and length of magnet
12
747 A toroid having average diameter ( 2.5 mathrm{m} ) number A turns ( 400, ) current ( =2 A ) and
magnetic field has 10 T what will be induced magnetic field (in amp/m).
A ( cdot frac{10^{5}}{4 pi} )
в. ( frac{10^{8}}{4 pi} )
c. ( frac{10^{8}}{2 pi} )
D. ( frac{10^{2}}{2 pi} )
12
748 A current of i ampere is flowing through each ofthe bent wires as shown the
magnitude and direction of magnetic field at 0 is
A ( cdot frac{mu_{0} mathrm{i}}{4}left(frac{1}{mathrm{R}}+frac{2}{mathrm{R}^{prime}}right) )
В. ( frac{mu_{0} mathrm{i}}{4}left(frac{1}{mathrm{R}}+frac{3}{mathrm{R}^{prime}}right) )
c. ( frac{mu_{0} text { i }}{8}left(frac{1}{R}+frac{3}{2 R} primeright) )
D. ( frac{mu_{0} mathrm{i}}{8}left(frac{1}{mathrm{R}}+frac{3}{mathrm{R}^{prime}}right) )
12
749 A particle of mass ( 2 times 10^{-5} k g ) moves
horizontally between two horizontal plates of a charged parallel plate capacitor between which there is an electric field of ( 200 N C^{-1} ) acting upward. A magnetic induction of ( 2.0 T ) is applied at right angles to the electric field in a direction normal to both ( vec{B} ) and
( vec{v} ). If ( g ) is ( 9.8 m s^{-2} ) and the charge on the
particle is ( 10^{-6} C, ) then find the velocity of charge particle so that it continues to move horizontally
( mathbf{A} cdot 2 m s^{-1} )
B. 20 ( m s^{-1} )
c. ( 0.2 m s^{-1} )
D. ( 100 mathrm{ms}^{-1} )
12
750 A current I flows in a circular arc of
radius R, which subtends an angle ( frac{pi}{6} ) radian at the center. The magnetic induction B at the center is
( A cdot frac{I_{l d}}{4 R_{D}} )
B. ( frac{I_{mu}}{2_{R}} )
c. ( frac{I mu_{0}}{24 R_{0}} )
D. ( frac{I mu_{0}}{12 R_{R}} )
12
751 Two identical current carrying coaxial
loops, carry current I in opposite sense. A simple amperian loop passes through both of them once. Calling the loop as ( C )
then which statement is correct?
This question has multiple correct options
( mathbf{A} cdot oint bar{H} cdot overline{d l}=mp 2 mu_{0} I )
B. the value of ( oint bar{H} . bar{d} l ) is independent of sense of ( C ).
C. there may be a point on C where B and ( d l ) are parallel.
D. none of these
12
752 A charged particle begins to move from the origin in a region which has a
uniform magnetic field in the ( x- )
direction and a uniform electric field in
the ( y- ) direction. Its speed is ( v ) when it
reaches the point ( (x, y, z) . ) Then, ( v ) will
depend
A. only on ( x )
B. only on ( y )
c. on both ( x ) and ( y ), but not ( z )
D. on ( x, y ) and ( z )
12
753 A long solenoid of radius ( 2 mathrm{cm} ) has 100
turns/cm and carries a current of ( 5 A ). A
coil of radius ( 1 mathrm{cm} ) having 100 turns and a total resistance of ( 20 Omega ) placed inside the solenoid co-axially. The coil is connected to galvanometer. If current in the solenoid is reversed in direction.
Fine the charge flow through the galvanometer.
A ( cdot 2 times 10^{-4} mathrm{C} )
B. ( 1 times 10^{-4} mathrm{C} )
c. ( 4 times 10^{-4} mathrm{c} )
D. ( 8 times 10^{-4} mathrm{C} )
12
754 A particle of charge ( q ) and mass ( m ) is moving through a region of space at right angles to an electric field and a
magnetic field, where the crossed magnetic and electric fields produce a zero net force on the charge. If the speed of the charge is doubled, which of the following changes will again produce a zero net force on the charge? This question has multiple correct options
A ( cdot ) Reducing the Electric field to ( frac{1}{2} E )
B. Increasing the Electric field to ( 2 E )
c. Reducing the Magnetic field to ( frac{1}{2} B )
D. Increasing the Magnetic field to ( 2 B )
E. Doubling both the Magnetic and Electric Fields
12
755 A particle of charge ( 16 times 10^{-18} C )
moving with velocity ( 10 m / s ) along the
X-axis enters a region where a
magnetic field of induction ( B ) is along the ( Y ) -axis, and an electric field of
magnitude ( 10 V m^{-1} ) is along the negative Z-axis. If the charged particle continues moving along the X-axis, the
magnitude of ( B ) is :
A ( cdot 1 W b / m^{2} )
B . ( 10^{5} mathrm{Wb} / mathrm{m}^{2} )
( mathbf{c} cdot 10^{6} W b / m^{2} )
D. ( 10^{-3} W b / m^{2} )
12
756 (i) Define ampere in terms of force
between two current carrying
conductors.
(ii) What is an ideal transformer?
12
757 to detect small alternating currents. Which of the diagrams shows how a
diode could be connected in order to
make conversion?
( A )
B.
( c )
D.
12
758 A particle with a specific charge ( mathrm{S} ) is fired with a speed ( V ) towards a wall at a
distance d, perpendicular to the wall. The minimum magnetic field that must exist in this region for the particle to not hit the wall is :
A ( cdot frac{V}{s d} )
в. ( frac{2 V}{s d} )
c. ( frac{V}{2 s d} )
D. ( frac{V}{4 s d} )
12
759 A charged particle moves through a magnetic field in a direction perpendicular to it. Then the
A. Speed of the particle remains unchanged
B. Direction of the particle remains unchanged
c. Acceleration remains unchanged
D. Velocity remains unchanged
12
760 (a) What is shunt?
(b) State Ampere’s circuital law. Using the law, obtain an expression for the
magnetic field well aside the solenoid of finite length.
12
761 The magnetic field around a currentcarrying coil lasts.
A. For three hours
B. As long as current flows thorugh it
c. Till its half-life period
D. Field is permanent
12
762 A proton of charge ( e ) and mass ( m_{p} )
moves in a circular path of radius ( r ) in a
uniform magnetic field ( boldsymbol{B} )
The momentum of the proton can be
described by the expression:
( mathbf{A} cdot e B r )
B. ( 2 e B r )
( c cdot e B r^{2} )
D. ( e B r m_{p} )
E ( cdot 2 e B r m_{p} )
12
763 The magnetic induction at the centre 0
of the arc due to current in portion ( boldsymbol{A B} )
will be
A. zero
в. ( frac{mu_{0} i}{r} )
c. ( frac{mu_{0} i}{2 r} )
D. ( frac{mu_{0}}{4 r_{0}} )
12
764 Two parallel wires carrying currents ( boldsymbol{I}_{1} )
and ( I_{2} ) in opposite directions and
separated by a distance ( d ) experience a
A . Replusive force ( mu_{0} I_{1} I_{2} / 2 pi d )
B. Attractive force ( mu_{0} I_{1} I_{2} / 2 pi d )
C. Repulsive force ( mu_{0} I_{1} I_{2} / 2 pi d^{2} )
D. Attractive force ( mu_{0} I_{1} I_{2} / 2 pi d^{2} )
12
765 A long straight wire carries a current 10 amp. An electron travels with a velocity ( mathbf{5 . 0} times mathbf{1 0}^{mathbf{6}} mathrm{m} / mathrm{sec} ) parallel to the wire 0.1
( mathrm{m} ) away from it and in a direction
opposite to the current. What force does the magnetic field of current exert on the electron?
В. ( 0.8 times 10^{-16} N )
c. ( 1.6 times 10^{-17} N )
D. ( 1.6 times 10^{-16} N )
12
766 In a long straight conductor carrying current, if the current is tripled and the
distance of the point from the conductor
is doubled, then the ratio of new
magnetic induction to old magnetic
induction is
A .3: 2
B . 2: 3
( c cdot 4: 9 )
9: 4
12
767 A circular coil of 20 turns and ( 10 mathrm{cm} )
radius is placed in a uniform magnetic
field of ( 0.10 T ) normal to the plane of the
coil. If the current in the coil is ( 5 A )
cross-sectional area is ( 10^{-5} m^{2} ) and coil
is made up of copper wire having free
electron density about ( 10^{29} m^{-3}, ) then the average force on each electron in
the coil due to magnetic field is.
( mathbf{A} cdot 2.5 times 10^{25} N )
B . ( 5 times 10^{25} N )
C ( .4 times 10^{25} N )
D. ( 3 times 10^{25} N )
12
768 Two parallel wires ( P ) and ( Q ) carry electric currents of ( 10 A ) and ( 2 A ) respectively in mutually opposite directions. The
distance between the wires is ( 10 mathrm{cm} ). If
the wire ( P ) is of infinite length and wire ( mathrm{Q} ) is ( 2 m ) long, then the force acting ( mathrm{Q} )
will be
( mathbf{A} cdot 4 times 10^{-5} N )
B. ( 8 times 10^{-5} N )
c. ( 6 times 10^{-5} N )
D. ( 14 times 10^{-5} N )
12
769 A triangular loop of side ( l ) carries a
current ( i . ) It is placed in a magnetic field B such that the plane of the loop is in
the direction of ( B ). The torque on the
loop is:
A . ( i )Вᅵ
В ( cdot i^{2} N l )
( ^{mathrm{c}} cdot frac{sqrt{3}}{4} B i l^{2} )
D. infinity
12
770 A proton is travelling along the ( x ) direction with velocity ( 5 times 10^{6} m s^{-1} )
The magnitude of force experienced by
the proton in a magnetic field ( B= ) ( (0.2 hat{i}+0.4 hat{k}) ) tesla is
A. ( 3.2 times 10^{-13} N )
N
В. ( 5.3 times 10^{-13} N )
c. ( 3.2 times 10^{13} N )
D. ( 6.3 times 10^{-13} ) 3
E ( .3 .5 times 10^{-12} N )
12
771 Two long current carrying thin wires, both with current ( I ), are held by
insulating threads of length ( L ) and are in equilibrium as shown in the figure, with threads making an angle ‘ ( boldsymbol{theta}^{prime} ) with
the vertical. If wires have mass ( lambda ) per
unit length then the value of ( I ) is ( :(g= )
gravitational acceleration)
A ( cdot 2 sqrt{frac{pi g L}{mu_{0}} tan theta} )
B. ( 2 sin theta sqrt{frac{pi lambda g L}{mu_{0} cos theta}} )
c. ( sin theta sqrt{frac{pi lambda g L}{mu_{0} cos theta}} )
D. ( sqrt{frac{pi lambda g L}{mu_{0}}} tan theta )
12
772 (a) An em wave is travelling in a medium with a velocity ( vec{v}=v hat{i} ). Draw a
sketch showing the propagation of the em wave, indicating the direction of the oscillating electric and magnetic fields.
(b) How are the magnitudes of the electric and magnetic fields related to
the velocity of the em wave?
12
773 A charged particle having charge ( 10^{-6} C ) and mass of ( 10^{-10} k g ) is fired
from the middle of the plate making an
angle ( 30^{circ} ) with plane of the plate. Length
of the plate is ( 0.17 mathrm{m} ) and it is sperated
by 0.1 m.Electric field ( E=10^{-3} N / C ) is
present between the plates.Just outside the plates magnetic field is present. Find the velocity of projection of charged particle and magnitude of the magnetic field perpendicular to the plane of the figure,if it has to graze the plate at ( C ) and ( A ) parallel to the surface of the plate .(Neglect gravity)
12
774 Assertion
A cyclotron cannot accelerate neutrons.
Reason
Neutrons are neutral.
A. Both Assertion and Reason are correct and Reason is
the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
775 Find the magnitude and direction of the force vector applied to the loop if the
vector ( vec{p}_{m} ) is parallel to the straight conductor.
A ( cdot vec{F}=20 )
В . ( vec{F}=10 )
c. ( vec{F}=0 )
D. ( vec{F}=50 )
12
776 The ratio of the diameters of wires of
circular and straight parts is
( ^{A} cdot frac{1}{sqrt{2}} )
B. ( frac{2 sqrt{3}}{pi} )
( c cdot frac{3 sqrt{3}}{2 pi} )
( D cdot sqrt{2} )
12
777 A very long straight wire carries a
current ( I . ) At the instant when a charge
( +Q ) at point ( P ) has velocity ( vec{v}, ) as shown in figure, the force on charge is
A. along OY
B. opposite to OY
c. along ox
D. opposite to OX
12
778 A wire of length ( l ) carries a current ( i ) along x-axis. A magnetic field exits given by ( boldsymbol{B}=boldsymbol{B}_{0}(hat{boldsymbol{i}}+hat{boldsymbol{j}}+hat{boldsymbol{k}}) boldsymbol{T} ). The
magnitude of the magnetic force acting on the wire is
A ( . i l B_{0} )
в. ( sqrt{3} B_{0} ) il
c. ( 2 i l B_{0} )
D. ( sqrt{2} B_{0} ) il
12
779 A current I ampere flows along an infinitely long straight thin walled hollow metallic cylinder of radius ( r . ) The magnetic field at any point inside the cylinder at a distance ( x ) from the axis of the cylinders is:
A ( cdot frac{mu_{0} I}{4 pi r} )
В. ( frac{mu_{0} I}{2 pi r} )
c. ( frac{mu_{0} I}{2 pi x} )
D. zero
12
780 singly ionized helium(x), ionized deuteron(y), alpha(z) particles are projected into a uniform magnetic field ( mathbf{3} times mathbf{1 0}^{-4} ) Tesla with velocities ( 10^{5} boldsymbol{m} boldsymbol{s}^{-1} )
( 0.4 times 10^{4} m s^{-1} ) and ( 2 times 10^{3} m s^{-1} )
respectively. The correct relation between the ratio of the angular momentum to the magnetic moment of the particles is :
A. ( x>y=z )
в. ( x<y<z )
c. ( x<zx>y )
12
781 Three long straight parallel wires
( X, Y, Z ) carry currents as shown; the
resultant force on ( Y ) is
A. Towards ( X )
B. Towards ( Z )
C. Perpendicular to the plane of the figure
D. Zero
12
782 A uniform electric field and a uniform
magnetic field are acting along the same direction in a certain region. If an
electron is projected along the direction of the fields with a certain velocity then
A. its velocity will increase
B. its velocity will decrease
c. it will turn towards left of its motion
D. it will turn towards right of its motion
12
783 Protons move rectilinearly in the region
of space where there are uniform
mutually perpendicular electric and magnetic fields ( mathrm{E} ) and B.The trajectory
of protons lies in the plane ( x z ) as shown
in the figure and forms an angle ( theta ) with
X-axis.Find the pitch of the helical
trajectory along which the protons will
move after the electric field is switched
off.
12
784 A demagnetize a small ferromagnet, a current of ( 2 A ) is required to be passed
in a solenoid of length ( 20 mathrm{cm} ) and
number of turns 100. The coercivity of
the magnet is:
B. ( 1000 A m^{-1} )
c. ( 1250 A m^{-1} )
D. ( 3750 A m^{-1} )
12
785 Figure shows a bar magnet and a long
straight wire ( mathrm{W} ), carrying current into
the
plane of paper.Point ( P ) is the point of intersection of axis of magnet and the
line
of shortest distance between magnet
and the wire. If ( P ) is the midpoint of the
magnet, then which of the following
statements is correct?
A. magnet experiences a torque in clockwise direction
B. magnet experiences a torque in anticlockwise direction
C. magnet experiences a force, normal to the line of shortest distance
D. magnet experiences a force along the line of shortest distance
12
786 An equilateral triangular loop is kept
near to a current carrying long wire as
shown in figure. Under the action of magnetic force alone, the loop
A. must move along positive or negative X-axis
B. must move in XY plane and not along X- of Y- axis
c. does not move
D. moves but which way we cannot predict
12
787 A long solenoid has 200 turns per cm
and carries a current I. The magnetic field at its centre is ( 6.28 times )
( 10^{-2} W b / m^{2} . ) Another long solenoid has
100 turns per ( mathrm{cm} ) and it carries a
current i/3. The value of the magnetic
field at its centre is
A ( cdot 1.05 times 10^{-2} mathrm{Wb} / mathrm{m}^{2} )
B . ( 1.05 times 10^{-5} mathrm{Wb} / mathrm{m}^{2} )
c. ( 1.05 times 10^{-3} mathrm{Wb} / mathrm{m}^{2} )
D. ( 1.05 times 10^{-4} mathrm{Wb} / mathrm{m}^{2} )
12
788 A positively charged particle, having charge ( q, ) is accelerated by a potential difference V. This particle moving along the ( x ) -axis enters a region where an electric field ( mathrm{E} ) exists. The direction of
the electric field is along positive y-axis. The electric field exists in the region
bounded by the line ( x=0 ) and ( x=a )
Beyond the line ( x=a ) (i.e., in the region
( x>a ) ), there exists a magnetic field of
strength B, directed along the positive y-axis. Find the pitch of the helix formed
after the particle enters the region ( x geq )
a. (Mass of the particle is ( m ) )
12
789 A charged particle moving in a magnetic field experiences a resultant force ?
A. In the direction opposite to the field
B. In the direction of field
c. In the direction perpendicular to both the field and its velocity
D. None of the above
12
790 A conductor (shown in the figure) carrying constant current I is kept in
the ( x ) -y plane in a uniform magnetic field ( vec{B} ). If ( F ) is the magnitude of the total
magnetic force acting on the conductor, then the correct statement(s) is (are)
This question has multiple correct options
( mathbf{A} cdot ) if ( vec{B} ) is along ( hat{z}, F propto(L+R) )
B. if ( vec{B} ) is along ( widehat{x}, F=0 )
C. if ( vec{B} ) is along ( hat{y}, F propto(L+R) )
D. if ( vec{B} ) is along ( hat{z}, F=0 )
12
791 A closed curve encircles several conductors.The line integral ( int overrightarrow{boldsymbol{B}} cdot boldsymbol{d} overrightarrow{boldsymbol{l}} )
around this curve is ( 3.83 times 10^{-7} T-m )
What is the net current in the
conductors?
A . ( 0.1 A )
в. ( 0.2 A )
( c .0 .3 A )
D. ( 0.4 A )
12
792 An infinite number of electric charges each equal to 2 nano coulombs in
magnitude are placed along ( x ) -axis at ( x=1 mathrm{cm}, x=3, quad x=9 mathrm{cm}, x=27 mathrm{cm} )
and so on. In these setup if the consecutive charges have oppsoite ( operatorname{sign}, ) then the electric potential at ( x=0 ) will be?
12
793 A neutron, a proton, an electron and an
( boldsymbol{alpha}- ) particle enter a region of uniform
magnetic field with the same velocities.
The magnetic field is perpendicular and
directed into the plane of the paper. The
tracks of the particles are labelled in
the figure. The electron follows the track
Q Magnetic field
( A . D )
B. ( B )
( c cdot C )
( mathbf{D} cdot A )
12
794 A current of ( 10 mathrm{A} ) is flowing in a wire of length 1.5 m. When it is placed in a uniform magnetic field of 2 Tesla then a force of ( 15 mathrm{N} ) acts on it. The angle between the magnetic field and the direction of current flow will be :
A ( .30^{circ} )
B . ( 45^{circ} )
( c cdot 60^{circ} )
D. ( 90^{circ} )
12
795 In a moving coil galvanometer a radial magnetic field is applied with concave magnetic poles, to have
A) uniform magnetic field
B) the plane of the coil parallel to field Choose the correct option among the following
A. both A and B are true
B. both A and B false
c. A is true, B is false
D. A is false, B is true
12
796 What current density is required to
provide a pressure difference of 1 atm
between any two points if ( B=2.2 T ) and
( l=35 m m )
A ( .1 .4 times 10^{3} mathrm{Am}^{-2} )
в. ( 7.2 times 10^{6} ) Ат ( ^{-} )
c. ( 1.3 times 10^{5} mathrm{Am}^{-2} )
D. ( 1.3 times 10^{6} mathrm{Am}^{-2} )
12
797 A circular coil of closely wound N turns
and radius r carries a current I. If the
expressions of The magnetic field at its centre is ( frac{mu_{0} N i}{x R} . ) Find ( x )
12
798 In the statement of Fleming’s left hand rule, force acting on the conductor is is
represented by
A. thumb
B. fore finger
c. middle finger
D. none
12
799 Two long thin parallel conductors of the
shape shown in figure above carry
direct currents ( I_{1} ) and ( I_{2} ). The separation
between the conductors is ( a ), the width
of the right-hand conductor is equal to ( b )
With both conductors lying in one
plane, the magnetic interaction force between them reduced to a unit of their length is given as ( F_{1}=frac{mu_{0} I_{1} I_{2}}{x pi b} ln frac{a+b}{a} )
Find ( boldsymbol{x} )
12
800 Three wires are carrying same constant current ( i ) indifferent directions. Four
loops enclosing the wires in different
manners are shown in figure. The direction of ( d vec{l} ) is shown in figure.
12
801 A rectangular coil of a moving coil galvanometer contains 100 turns, each
having area ( 15 c m^{2} . ) It is suspended in
the radial magnetic field ( 0.03 mathrm{T} ). The twist constant of suspension fibre is
( 15 times 10^{-10} mathrm{N}-mathrm{m} / ) degree. Calculate the sensitivity of the moving coil galvanometer.
12
802 A proton, a deutron and an ( alpha ) particle
accelerated through the same potential difference enter a region of uniform magnetic field, moving at right angles
to ( B ). What is the ratio of their radii.?
A .2: 1: 1
B. ( 1: sqrt{2}: sqrt{2} )
c. 1: 2: 1
D. 1: 1: 2
12
803 An alpha-particle (charge 2e) moves
along a circular path of radius ( 1 A ) with
a uniform speed of ( 2 times 10^{6} m s^{-1} )

Calculate the magnetic field produced at the centre of the circular path

12
804 A positively charged particle (proton) is projected towards east.The magnetic field is towards south.The particle will
be deflected towards
A. North
B. Down
c. up
D. west
12
805 If an electron is moving with velocity ( bar{v} ) produces a magnetic field ( bar{B} ), then
A. the direction of field ( bar{B} ) will be same as the direction of
velocity ( bar{v} )
B. the direction of field ( bar{B} ) will be opposite as the direction of velocity ( bar{v} )
C. the direction of field ( bar{B} ) will be perpendicular as the direction of velocity ( bar{v} )
D. the direction of field ( bar{B} ) does not depend upon the direction of velocity ( bar{v} )
12
806 A conducting gas is in the form of a long cylinder. Current flows through the gas along the length of the cylinder. The current is distributed uniformly across
the cross-section of the gas. Disregard thermal and electrostatic forces among
the gas molecules. Due to the magnetic fields set up inside the gas and the
forces which they exert on the moving ions, the gas will tend to
A. expand
B. contract
c. expand and contract alternately
D. none of the above
12
807 A positive charge ‘q’ of mass ‘m’ is moving along the +x axis. We wish to apply a uniform magnetic field ( B ) for
time ( Delta t, ) so that the charge reverses its
direction, crossing the y axis at a distance ( d ). Then:
A ( cdot B=frac{m v}{q d} ) and ( Delta t=frac{pi d}{v} )
B. ( B=frac{m v}{2 q d} ) and ( Delta t=frac{pi d}{2 v} )
c. ( _{B}=frac{2 m v}{q d} ) and ( Delta t=frac{pi d}{2 v} )
D. ( B=frac{2 m v}{q d} ) and ( Delta t=frac{pi d}{v} )
12
808 Assertion
A charged particle moves along positive y-axis with constant velocity in uniform electric and magnetic fields.If magnetic field is acting along positive ( x ) -axis,then electric field should act along positive z-axis.
Reason
To keep the charged particle undeviated the relation ( vec{E}=vec{B} times vec{v} ) must hold good.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
809 A straight steel wire of length ( l ) has
magnetic moment ( m ). If the wire is bent
in the form of a semicircle, the new
value of the magnetic dipole moment is
A . ( m )
в. ( frac{m}{2} )
( c cdot frac{m}{pi} )
D. ( frac{2 m}{pi} )
12
810 Derive an expression for magnetic field strength at any point on the axis of a circular current carrying loop using Biot-Savart’s law. 12
811 Electrons at rest are accelerated by a potential of ( V ) volt. These electrons enter the region of space having a uniform, perpendicular magnetic induction field
B. The radius of the path of the electrons inside the magnetic field is?
A ( cdot sqrt{(m e V) / B e} )
B. ( sqrt{(2 m e V) / B e} )
( mathbf{c} cdot sqrt{(m e V) / 2 B e} )
D. None of these
12
812 A galvanometer of resistance ( 50 Omega ) is
connected to a battery of ( 3 V ) along with a resistance of ( 2950 Omega ) in series. A full-
scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be equal
to
A . ( 5050 Omega )
B. ( 5550 Omega )
c. ( 6050 Omega )
D. ( 4450 Omega )
12
813 The value of magnetic field due to a small element of current carrying conductor at a distance r and lying on
the plane perpendicular to the element of conductor is
A. zero
B. Maximum
c. Inversely proportional to the current
D. None of the above
12
814 In cyclotron the resonance condition is:
A. the frequency of revolution of charged particle is equal to the frequency of A.C. voltage sources
B. the frequency of revolution of charged particle is equal to the frequency of applied magnetic field
C. the frequency of revolution of charged particle is equal to the frequency of rotation of earth
D. the frequency of revolution of charged particle, frequency of A.C. source and frequency of magnetic field are equal
12
815 Two free parallel wires carrying currents
in the opposite directions
A. attract each other
B. repel each other
C. do not affect each other
D. get rotated to be perpendicular to each other
12
816 A person who is moving parallel to the
charge and at the same velocity as the
charge will measure.
A. A magnetic field and an electric field due to the moving charge.
B. A magnetic field, but not an electric field due to the moving charge.
C. An electric field, but not a magnetic field due to the moving charge.
D. Neither an electric field nor a magnetic field due to the moving charge.
E. A decrease in the amount of charge.
12
817 Assertion
A wire bent into an irregular shape with
the points ( P ) and ( Q ) fixed. If a current
passed through the wire, then the area
enclosed by the irregular portion of the wire increases.
Reason
Opposite currents carrying wires repel
each other.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
818 A certain current on passing through a galvanometer produces a deflection of 100 divisions. When a shunt of one ohm
is connected, the deflection reduces to
1 division. The galvanometer resistance is
A. ( 100 Omega )
B. ( 99 Omega )
( c .10 Omega )
D. ( 9.9 Omega )
12
819 A circular loop of radius ( 1 mathrm{m} ) is kept in a magnetic field of strength 2 T directed
perpendicular to the plane of loop.
Resistance of the loop wire is ( 2 mathrm{m} . mathrm{A} )
conductor of length ( 2 mathrm{m} ) is sliding with a speed ( 1 mathrm{m} / mathrm{s} ) as shown in the figure. Find
the instantaneous force acting on the rod [Assume that the rod has negligible resistance]
( A cdot 8 N )
B. 16 N
( c .24 mathrm{N} )
D. 32
12
820 Two concentric coils of radius ( r ) are
kept mutually perpendicular to each other. If current flowing through both
the coils is ( I, ) then the resultant
magnetic moment due to the two coils will be
A . ( sqrt{2} I pi r^{2} )
В. ( sqrt{2} I r^{2} )
c. ( sqrt{2} I r )
D. ( 2 pi r^{2} )
12
821 If a conducting rod ( A B ) placed in a uniform magnetic field pointing in positive z-direction (as shown in figure), moves parallel to y-axis, then
end ( A ) of the rod will be
A. Neutral
B. Positively charged
c. Negatively charged
D. None of these
12
822 A helium nucleus makes a full rotation
in a circle of radius ( 0.8 m ) in 2 sec. The
value of the magnetic field induction ( boldsymbol{B} )
in tesla at the centre of circle will be
A ( cdot 2 times 10^{-19} mu_{0} )
B . ( 10^{-19} / mu_{0} )
( mathbf{c} cdot 10^{-19} varphi_{0} )
D. ( 2 times 10^{-20} / mu_{0} )
12
823 In a current-carrying solenoid, the magnetic field direction is given by the
right hand rule such that the
A. Encircling fingers indicate the direction of electric current
B. Encircling fingers indicate the direction of magnetic field
C. Extended right thumb will point in the direction of the axial magnetic field
D. Both (2) and (3)
12
824 Distance between two very long parallel wires is ( 0.2 m . ) Electric currents of ( 4 A ) in
one wire and ( 6 A ) in the other wire are
passing in the same direction. Find the position of a point on the perpendicular line joinig the two wires at which the magnetic field intensity is zero.
12
825 A solenoid is
A . an electromagnet
B. a temporary magnet
C. a permanent magnet
D. Both 1 and 2
12
826 A loop of magnetic moment ( overrightarrow{boldsymbol{M}} ) is placed in the orientation of unstable equilibrium position in uniform magnetic field ( vec{B} ). The external work
done in rotating it through an angle ( theta ) is
A. ( -M B(1-cos theta) )
B. ( -M B(cos theta) )
( mathbf{c} cdot M B cos theta )
D. ( M B(1-cos theta) )
12
827 If a current carrying wire carries 10 A
current then the magnetic field is
X. Now the current in the wire increases
to 100 A, them magnetic field in the wire becomes
( A cdot>x )
B.
D. all
December 27, 2019
Yashassvi Padigala
( B )
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12
828 If ( mu_{r} ) be the relative permeability and ( varepsilon_{r} ) be the relative dielectric constant of a
medium, its refractive index is:
( ^{A} cdot frac{1}{sqrt{mu_{r} epsilon_{r}}} )
в. ( frac{1}{mu_{t} epsilon_{r}} )
c. ( sqrt{mu_{r} epsilon_{r}} )
D. ( mu_{r} epsilon_{r} )
12
829 Derive the expression for magnetic field at a point on the axis of a circular
current carrying loop.
12
830 State condition when magnitude of force on a current carrying conductor placed in a magnetic field is zero.
A. When current in conductor is in the direction of magnetic field.
B. When current in conductor is perpendicular to the direction of magnetic field.
c. Always zero
D. None of these
12
831 A moving coil galvanometer has a coil of area ( A ) and number of turns ( N . A )
magnetic field ( mathrm{B} ) is applied on it. The torque acting on it is given by ( boldsymbol{tau}=boldsymbol{k} boldsymbol{i} )
where i is current through the coil. If moment of inertia of the coil is I about
the axis of rotation.
A charge ( Q ) is passed almost instantaneously through coil If the maximum angular deflection in it ( mathbf{s} boldsymbol{theta}=boldsymbol{Q} sqrt{frac{boldsymbol{pi} boldsymbol{N} boldsymbol{A} boldsymbol{B}}{boldsymbol{x} boldsymbol{I} boldsymbol{i}_{0}}} . ) Find ( mathbf{x} )
12
832 n the following diagram, which particle
has highest ( e / m ) value?
( A )
B.
( c )
( D )
12
833 Determine the force acting between two parallel current carrying conductor wires. Write theoretical definition of
ampere on this basis.
12
834 Which among the following is not an electronic component used in constructing a toroid?
A. copper wires
B. laminated iron
c. ferrite core
D. aluminium powder
12
835 Figure below shows two infinitely long
and thin current carrying conductors ( boldsymbol{X} )
and ( Y ) kept in vacuum, parallel to each
other, at a distance ( ^{prime} a )

How much force per unit length acts on
the conductor ( Y ) due to the current
flowing through ( X ? ) Write your answer in terms of ( left(frac{mu_{0}}{4 pi}right), I_{1}, I_{2} ) and ( a )
(Derivation of formula is not required)

12
836 A proton with kinetic energy ( 8 e V ) is moving in a uniform magnetic field. The kinetic energy of a deuteron moving in the same path in the same magnetic field will be:
A ( .2 e V )
B. ( 4 e V )
( c .6 e V )
D. ( 8 e V )
12
837 A wire is lying parallel to a square coil. Same current is flowing in same direction in both of them. The magnetic induction at any point P inside the coil
will be :
A . zero
B. more than that produced by only coil
c. less than that produced by only coil
D. equal to that produced by only coil
12
838 The magnetic field at the origin due to a current element ( i . vec{d} l ) placed at a
position ( vec{r} ) is This question has multiple correct options
A ( frac{mu_{0} i}{4 pi} frac{overrightarrow{d l} times vec{r}}{r^{3}} )
В. ( frac{mu_{0} i}{4 pi} frac{vec{r} times vec{d} l}{r^{3}} )
( ^{mathrm{C}}-frac{mu_{0} i}{4 pi} frac{vec{r} times vec{d} l}{r^{3}} )
D. ( -frac{mu_{0} i}{4 pi} frac{vec{d} l times vec{r}}{r^{3}} )
12
839 The force between two parallel conductors, each of length ( 50 mathrm{cm} ) and
distant ( 20 mathrm{cm} ) apart is ( 100 mathrm{N} ). If the current in one conductor is double that
in another one then the values will
respectively be(Given ( left.mu_{0}=4 pi times 10^{-7}right) )
B. ( 50 A ) and ( 100 A )
c. ( 10 A ) and ( 20 A )
D. ( 5 A ) and ( 10 A )
12
840 Two current carrying wires are a
distance ( a ) apart and experience a Force
( F ) between them. The wires are moved a
distance ( 2 a ) apart. Which of the following is a possible value for the new force between the
wires?
A ( cdot frac{1}{4} F )
в. ( frac{1}{2} )
( c . F )
D. ( 2 F )
E . ( 4 F )
12
841 Assertion
Current in wire-1 is in the direction as
shown in figure.The bottom wire is fixed.To keep the upper wire stationary current in it should be in opposite direction.
Reason
Under the above condition,equilibrium
of upper wire is stable.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
842 Figure shows a square loop of side ( 1 m )
and resistance 1Omega. The magnetic field on left side of line PQ has a magnitude
( B=1.0 T . ) The work done in pulling the
loop out of the field uniformly in ( 1 s ) is
4. 1
В. ( 10 J )
begin{tabular}{l}
( .0 .1 .] ) \
hline
end{tabular}
0.100
12
843 An electron is projected at an angle ( theta ) with a uniform magnetic field. If the pitch of the helical path is equal to its radius, then the angle of projection is
( mathbf{A} cdot tan ^{-1} pi )
В ( cdot tan ^{-1} 2 pi )
( mathbf{c} cdot cot ^{-1} pi )
D. ( cot ^{-1} 2 pi )
12
844 The magnetic field at the centre of a circular loop of area ( A ) is ( B ). The
magnetic moment of the loop is
A ( cdot frac{B A^{2}}{mu_{0} pi} )
B. ( frac{B A sqrt{A}}{mu} )
( ^{mathrm{c}} cdot frac{B A sqrt{A}}{mu_{0} pi} )
D. ( frac{2 B A sqrt{A}}{mu_{0} sqrt{pi}} )
12
845 A laser lamp is of ( 9 m W ) diameter ( = )
( 2 m m . ) Then what is the amplitude of
magnetic field associated with it?
A ( .49 mu T )
B. ( 98 mu T )
c. ( 9.8 mu T )
D. ( 4.9 mu T )
12
846 What is the trajectory of the charged particle if the initial velocity of the
particle is perpendicular to the direction of the magnetic field?
12
847 A short bar magnet placed with its axis at ( 30^{0} ) with a uniform external magnetic
field of ( 0.35 T ) experiences a torque of magnitude equal to ( 4.5 times 10^{-2} mathrm{N} ) m. The
magnitude of magnetic moment of the given magnet is
A ( cdot 26 J T^{-1} )
B . ( 2.6 J T^{-1} )
c. ( 0.26 J T^{-1} )
D. ( 0.026 J T^{-1} )
12
848 In a moving coil galvanometer, the deflection of the coil ( theta ) is related to the
electric current ( i ) by the relation
A. ( i propto tan theta )
В ( . i propto theta )
( mathbf{c} cdot i propto theta^{2} )
( D cdot i propto sqrt{theta} )
12
849 If the value of ( theta ) increases then the
magnetic moment value
A. Increases
B. Decreases
c. Remains same
D. Cannot be said
12
850 law gives the quantitative relationship between current and magnetic field due to the
current carrying conductor.
12
851 Which line shows the path of gamma
radiation in a magnetic field?
( A )
B.
( c )
0.0
( E )
12
852 Mark the incorrect option.
A. Ampere’s law states that flux ( B ) through any closed
surface is ( mu_{0} ) times the current passing through the area bounded by closed sourface
B. Gauss’s law for magnetic field in magnetostatics serves the same purpose as Gauss’s law for electric for electric field in electrostatics
C. Gauss’s law for magnetic field states that the flux of ( B ) through any closed surface is always zero, whether or not there are currents within the surface
D. All the above
12
853 A uniform electric field and a uniform
magnetic field are produced pointing in the same direction. An electron is
projected with its velocity pointed in the
same direction.Then:
A. the electron will turn to its right
B. the electron will turn to its left
c. the electron velocity will increase in magnitude
D. the electron velocity will decrease in magnitude
12
854 Two circular coils are made of two
identical wires of the same length. If the number of turns of the two coils are 4
and ( 2, ) then the ratio of magnetic inductions at the centres will be:
( A cdot 4: 1 )
B. 2:
( c cdot 1: 2 )
D. 1:
12
855 Figure shows three cases: in all cases
the circular part has radius ( r ) and
straight ones are infinitely long. For the
same current the ratio of field ( B ) at
center ( P ) in the three cases ( B_{1}: B_{2}: B_{3} )
is :
( ^{mathrm{A}} cdotleft(-frac{pi}{2}right):left(frac{pi}{2}right):left(frac{3 pi}{4}-frac{1}{2}right) )
( ^{mathrm{B}} cdotleft(-frac{pi}{2}+1right):left(frac{pi}{2}+1right):left(frac{3 pi}{4}+frac{1}{2}right) )
( ^{c} cdotleft(-frac{pi}{2}right):left(frac{pi}{2}right):left(frac{3 pi}{4}right) )
( left(-frac{pi}{2}-1right):left(frac{pi}{2}-frac{1}{4}right):left(frac{3 pi}{4}+frac{1}{2}right) )
12
856 A galvanometer gives full scale deflection of 1 volt when acting like a voltmeter when connected in series
with ( 2 k Omega ) resistance. The same
galvanometer gives ( 500 mathrm{mA} ). Full scale deflection when acting like a ammeter
when connected with shunt resistance
of value ( 0.2 Omega ) in parallel. Find out the resistance of galvanometer
12
857 State whether the given statement is True or False.

The magnetic lines of force are always parallel to a straight conductor carrying an electric current.

12
858 When a solenoid is activated, the force
that moves the plunger is
A. an electromagnetic field
B. a permanent magnetic field
c. varying voltage
D. a steady current
12
859 The sensitiveness of a moving coil galvanometer can be increased by decreasing
A. the number of turns in the coil
B. the area of coil
c. the magnetic field
D. the couple per unit twist of the suspension
12
860 Three long straight wires ( A, B ) and ( C ) are carrying currents as shown in figure.
Then the resultant force on B is directed
A. perpendicular to the plane of the paper and outward
B. perpendicular to the plane of the paper and inward
c. towards ( A )
D. towards
12
861 A conductor of length 2 m carrying
current ( 2 mathrm{A} ) is held parallel to an infinitely long conductor carrying current of ( 12 mathrm{A} ) at a distance of ( 100 mathrm{mm} )
the force j on a small conductor is:
A ( cdot 8.6 times 10^{-5} N )
B. ( 6.6 times 10^{-5} N )
c. ( 7.6 times 10^{-5} N )
D. 9.6 ( times 10^{-5} N )
12
862 In Thomsons method, a beam of
electrons accelerated through a p.d. of ( 285 V, ) passes undeflected through
perpendicular electric and magnetic
fields of intensities ( 10^{5} V / m ) and
( 10^{-2} W b / m^{2} ) respectively. Then the value of e/m of electron is:
A ( cdot 1.75 times 10^{11} C / k g )
В. ( 1.66 times 10^{11} C / k g )
c. ( 1.84 times 10^{11} C / k g )
D. ( 1.89 times 10^{11} C / k g )
12
863 The magnetic field of a solenoid can be increased by
A. adding more loops per metre
B. increasing the current
c. putting an iron core inside the coil to make an electromagnet
D. All of the above
12
864 A long straight wire is carrying current
in ( +z ) direction. The ( x ) -y pkane contains a closed circular loop carrying current
( I_{2} ) and not encircling the straight wire. The force on the loop will be.
B . ( mu_{0} I_{1} I_{2} / 4 pi )
c. zero
D. Depends on the distance of the circle of the loop from the wire
12
865 A current carrying loop is placed in a uniform magnetic field in four different
orientations I, II, III and IV as shown in
figure. Arrange them in decreasing order of potential energy.
( A cdot|>|||>||>mid V )
B. |> || > ||| > IV
c. ।>IV> || > ||
12
866 Immediately below the current carrying wire a stream of electrons are projected parallel to the wire as shown. They will
be
A. accelerated to the right
B. retarded
D. deflected downwardd
12
867 The sensitivity of moving coil galvanometer can be increased by increasing
A. Number of turns of the coil
B. Magnetic field
c. Area of the coil
D. Couple per unit twist of suspension
12
868 A potential difference of ( 600 mathrm{V} ) is
applied across the plates of a parallel plate capacitor placed in a magnetic field. The separation between the plates is ( 3 mathrm{mm} . ) An electron projected vertically upward, parallel to the plates, with a velocity of ( 2 times 10^{6} m s^{-1} ) moves
undeflected between the plates. Find the magnitude and direction of the magnetic field in the region between the capacitor plates. Find the magnitude and direction of the magnetic field in the region between the capacitor plates. Given the Charge of the electron ( =-1.6 times 10^{-19} C )
12
869 An arbitrary shaped closed coil is made of a wire of length L and a current ampere is flowing in it. If the plane of the coil is perpendicular to magnitude field ( vec{B}, ) the force on the coil is?
A. zero
B . IBL
c. 2 IBL
D. ( frac{1}{2}^{18 L} )
12
870 An electron doesn’t suffer any deflection
while passing through a region of uniform magnetic field What is the direction of magnetic field?
12
871 A uniform magnetic field B is set up along the positive ( x ) -axis. A particle of charge ‘q’ and mass ‘m’ moving with a velocity v enters the field at the origin in ( X-Y ) plane such that it has velocity
components both along and perpendicular to the magnetic field B. Trace, giving reason, the trajectory followed by the particle. Find out the expression for the distance moved by the particle along the magnetic field in one rotation
12
872 Express ( 90 mathrm{cm} ) as a percent of ( 4.5 mathrm{m} ) 12
873 In an experiment electrons are accelerated,from rest, by applying a
voltage of ( 500 V . ) Calculate the radius of
the path if a magnetic field ( 100 m T ) is then applied.[Charge of the electron = ( 1.6 times 10^{-19} C ) Mass of the electron ( = )
( 9.1 times 10^{-31} k g )
A. ( 7.5 times 10^{-4} m )
В. ( 7.5 times 10^{-3} m )
( c .7 .5 m )
D. ( 7.5 times 10^{-2} mathrm{m} )
12
874 Two wires carrying current in opposite
directions are placed a distance ( a )
apart Which of the following will cause the greatest increase in the magnitude of the force between the wires?
A. Doubling the current in one wire.
B. Doubling the current in both wires.
c. Doubling the distance between the wires to ( 2 a )
D. Decreasing the distance between the wires to
E. Running the currents in the same direction
12
875 Answer the following questions:
(i) Obtain the expression for the cyclotron frequency.
(ii) A deuteron and a proton are accelerated by the cyclotron. Can both be accelerated with the same oscillator
frequency? Given reason to justify your
answer
12
876 A non-planar closed loop of arbitrary shape carrying a current ( I ) is placed in uniform magnetic field.The force acting on the loop
A. is zero only for one orientation of loop in magnetic field
B. is zero for two symmetrically located positions of loop in magnetic field
c. is zero for all orientations
D. is never zero
12
877 Which of the following observations are true for Hans Oersteds experiment?
a. When current passes through the
wire the compass needle comes to restt
in a direction along the Earths magnetic field.
b. When placed just above the wire, North Pole of the compass needle deflects towards the east when current
is passes from A to B.
c. When placed just below the wire, North Pole of the compass needle deflects towards the east when current is passes from B to A i.e. on reversing the direction of current
( A cdot ) a and ( c )
B. a and b
( c . ) b and ( c )
D. All of the above
12
878 A 2 MeV proton is moving perpendicular to uniform magnetic field of 2.5 T. The magnetic force on the proton.
A ( cdot 8 times 10^{-12} mathrm{N} )
B . ( 4 times 10^{-12} mathrm{N} )
c. ( 16 times 10^{-12} mathrm{N} )
D. ( 2 times 10^{-12} mathrm{N} )
12
879 toppr
Q Type your question
insulted from each other. The entire loop
lies in the plane (of the paper). A uniform magnetic filed ( vec{B} ) point into the
plane of the paper. At ( t=0 ), the loop
starts rotating about the common
diameter as axis with a constant
angular velocity ( omega ) in the magnetic field.
Which of the following option is/are
correct?
A. The rate of change of the flux is maximum when the plane of the loops is perpendicular to plane of the
paper
B. The net emf induced due to both the loops is proportional to cos ( omega t )
C. The emf induced in the loop is proportional to the sun of the areas of the two loops.
D. non of the above.
12
880 A toroid has a core (non -ferromagnetic) of inner radius ( 25 mathrm{cm} ) and outer radius
( 26 mathrm{cm}, ) around which 3500 turns of a
wire are wound. If the current in the wire
is ( 11 A, ) what is the magnetic field (a) outside the toroid,
(b) inside the core of
the toroid, and
(c) in the empty space surrounded by the toroid.
12
881 In an orbit of radius ( 0.4 A^{0} ) an electron
revolves with a frequency of ( 6.25 times 10^{15} )
Hz. The magnetic induction field at its
centre is (in Tesla):
A . ( 4 pi )
в. ( 2 pi )
( c cdot 4 )
( D cdot 2 )
12
882 Relation between magnetic moment and angular velocity is
( A . M propto omega )
B. ( M propto omega^{2} )
c. ( M propto sqrt{omega} )
D. None of these
12
883 A charge ‘q’ moves in a region where electric field and magnetic field both exist, then force on it is : –
( mathbf{A} cdot q(vec{V} times vec{B}) )
B ( cdot q vec{E}+q(vec{V} times vec{B}) )
( mathbf{c} cdot q vec{E}+q(vec{B} times vec{V}) )
( mathbf{D} cdot q vec{B}+q(vec{E} times vec{V}) )
12
884 A loosely wound helix made of stiff wire is mounted vertically with the lower end just touching a dish of mercury when a current from the battery is started in
the coil through the mercury
A. the wire oscillates
B. the wire continues making contact
c. the wire breaks contact just when the current is passed
D. the mercury will expand by heating due to passage of current
12
885 A current is passed through a straight wire. The magnetic field established
around it has its lines of forces:
A . circular
B. parabolic
c. elliptical
D. no fixed shape
12
886 The force on a charged particle moving through a magnetic field is maximum when
A. Moving with the field
B. Moving against the field
C. Moving at a ( 45^{circ} ) angle to the field
D. Moving at a ( 90^{circ} ) angle to the field
E. The particle will not be affected
12
887 A circular coil of 100 turns has an
effective radius of ( 0.05 m ) and carries a
current of ( 0.1 A ). How much work is
required to turn it in an external
magnetic field of ( 1.5 W b / m^{2} ) through
( 180^{circ} ) about its axis perpendicular to the magnetic field? The plane of the coil is initially perpendicular to the magnetic field :
A . 0.456 .5
в. ( 2.65 J )
c. ( 0.2355 J )
D. 3.95J
12
888 (a) Write using Biot – Savart Law, the expression for magnetic field ( vec{B} ) due to an element ( overrightarrow{d l} ) carrying current ( I ) at a distance ( vec{r} ) from it in a vector form.
Hence derive the expression for the magnetic field due to a current carrying loop of radius ( R ) at a point ( P ) distant ( x ) from its centre along the axis of the
loop.
(b) Explain how Biot – Savart law enables one to express the Ampere’s circuital law in the integral form, viz.,
[
overrightarrow{boldsymbol{B}} cdot overrightarrow{boldsymbol{d}} boldsymbol{l}=boldsymbol{mu}_{boldsymbol{o}} boldsymbol{I}
]
where ( I ) is the total current passing through the surface.
12
889 A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. the
energy required to rotate it by ( 60^{circ} ) is ( W ) Now the torque required to keep the magnet in this new position is.
A. ( frac{2 W}{sqrt{3}} )
B. ( frac{W}{sqrt{3}} )
c. ( sqrt{3} W )
D. ( frac{sqrt{3}}{2} W )
12
890 Find the circulation of the vector ( vec{B} )
around the square path ( Gamma ) with side ( l )
located as shown in the figure above.
( mathbf{A} cdot oint vec{B} d r=2(1-mu) B l sin theta )
в. ( oint vec{B} d r=(1+mu) B l sin theta )
c. ( oint vec{B} d r=2(1-+mu) B l sin theta )
D. ( oint vec{B} d r=(1-mu) B l sin theta )
12
891 How toroid is different from solenoid. 12
892 Ratio of the currents ( I_{1} ) and ( I_{2} ) flowing
through the circular and straight parts
is
A ( cdot frac{sqrt{3}}{2 pi} )
B. ( frac{2 sqrt{3}}{5} )
( c cdot frac{3 sqrt{3}}{2 pi} )
D. ( frac{3 sqrt{3}}{2 sqrt{2} pi} )
12
893 A current carrying loop of radius ( 2 mathrm{cm} )
has ( 4 A ) current flowing in an anti-
clockwise direction. The plane of the loop makes an angle of ( theta ) with the direction of the magnetic field which is in an upward direction. the value of the
magnetic field is 0.7 Tesla.if potential
energy of loop in magnetic field is ( approx ) ( 0.01 J, ) then value of ( theta ) is:
A ( cdot 45^{circ} )
B . ( 60^{circ} )
( c .30^{circ} )
D. None of these
12
894 Following is square shape loop, whose one arm ( B C ) produces magnetic field ( B )
at the center of coil. The resultant
magnetic field due to all the arms will
be:
( A cdot 4 B )
в. ( B / 2 )
( c . B )
D. ( 2 B )
12
895 Find the resultant magnetic moment
when ( boldsymbol{theta}=mathbf{2 4 0}^{circ} )
( mathbf{A} cdot M / 4 pi )
в. ( 2 M / pi )
c. ( 3 M / pi )
D. ( 3 sqrt{3} M / 4 pi )
12
896 In the above question, the tension in the
two wires, if the direction of the current
is reversed, keeping the magnetic field the same is
A . 1.0
в. 2.0N
c. 3.0
D. 4.0N
12
897 In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field B. If ( mathrm{V} ) and ( mathrm{B} ) are kept constant, the ratio ( ( left.frac{text { Charge on the ion }}{text { Mass of the ion }}right) ) wil be proportional to
A ( -frac{1}{R} )
в. ( frac{1}{R^{2}} )
( c cdot R^{2} )
D.
12
898 ( 0.8 mathrm{J} ) work is done in rotating a magnet
by ( 60^{circ}, ) placed parallel to a uniform
magnetic field. How much work is done
in rotating it ( 30^{circ} ) further?
A ( cdot 0.8 times 10^{7} ) erg
B. ( 0.8 e r g )
( c .8 J )
D. 0.45
12
899 A long wire is bent into the shape
PQRST as shown in the following
Figure with ( Q R S ) being a semicircle
with centre ( O ) and radius ( r ) metre. ( A )
current of ( I ) ampere flows through it in
the direction ( boldsymbol{P} rightarrow boldsymbol{Q} rightarrow boldsymbol{R} rightarrow boldsymbol{S} rightarrow boldsymbol{T} )
Then, the magnetic induction at the
point ( O ) of the figure in vacuum is
( ^{mathbf{A}} cdot_{mu_{0} i}left[frac{1}{2 pi r}+frac{1}{4 r}right] )
В ( cdot mu_{0} ileft[frac{1}{2 pi r}-frac{1}{4 r}right] )
c. ( frac{mu_{0} i}{4 r} )
D. ( frac{mu_{0} i}{pi r} )
12
900 If ( epsilon_{0} ) and ( mu_{0} ) are, respectively, the electric
permittivity and magnetic permeability of free space, ( epsilon ) and ( mu ) are the corresponding quantities in a medium, the index of refraction of the medium in
terms of the above parameters is
A ( cdot sqrt{frac{mu epsilon}{mu_{0} epsilon_{0}}} )
в. ( sqrt{frac{epsilon}{mu_{0} epsilon_{0}}} )
c. ( sqrt{frac{2}{mu_{0} epsilon_{0}}} )
D. ( sqrt{frac{1}{mu_{0} epsilon_{0}}} )
12
901 A wire bent as shown in Figure carries a current ( I ). Find the magnetic field at ( P: )
A ( frac{mu_{0}}{4} )
в. ( frac{3 mu_{0}}{2 R} )
c. ( frac{7 mu_{0} I}{8 R} )
D. ( frac{mu_{0}}{8_{D}} )
12
902 A wire carrying current ( i ) has the configuration shown in the figure. Two semi-infinite straight sections, each tangent to the same circle, are
connected by a circular arc, of angle ( boldsymbol{theta} )
along the circumference of the circle,
with all sections lying in the same plane. What must ( theta ) (in rad) be in order
for ( B ) to be zero at the center of
the circle?
12
903 A galvanometer is shunted by ( frac{1}{r} ) of its
resistance. Find the fraction of total
current passing through the galvanometer.
12
904 For an ideal toroid, in which turns are closely spaced, the external magnetic field is
A. Very high
B. Infinity
c. zero
D. one
12
905 The figure above shows which magnetic instrument?
A. solenoid
B. power transformer
c. toroid
D. None of these
12
906 A circular coil a carrying current
produces a magnetic field ( B_{0} ) at its
centre. This coil is made itself to 10
turns and the same current is set up in
it. The magnetic field ( B ) at its centre
would be
A. ( B=B_{0} )
В. ( B=10 B_{0} )
c. ( B=50 B_{0} )
D. ( B=100 B_{0} )
12
907 A strong magnetic field is applied on a stationary electron. Then the electron:
A. moves in the direction of the field
B. remains stationary
c. starts spinning
D. moves opposite to the direction of the field
12
908 A rectangular loop carrying a current
is situated near a long straight wire such that the wire is parallel to the one
of the sides of the loop and is in the plane of the loop. If a steady current lis established in wire as shown in
the figure, the loop will
A. Rotate about an axis parallel to the wire
B. Move away from the wire or towards right
c. Move towards the wire
D. Remain stationary
12
909 When will the couple acting on the coil be
(i) maximum
(ii) minimum?
A. (i) When plane of coil is normal to the magnetic field,
(ii) When plane of coil is normal to the magnetic field
B. (i) When plane of coil is parallel to the magnetic field
(ii) When plane of coil is parallel to the magnetic field.
C. (i) When plane of coil is parallel to the magnetic field,
(ii) When plane of coil is normal to the magnetic field
D. None of the above
12
910 The diagram above shows a positively charged particle moving toward the right and about to enter a magnetic
field whose direction is shown by the
blue arrows.
What is the direction of the force on the
positively charged particle (from our point of view at the instant it enters the
magnetic field?
A. Right
B. Left
c. up
D. Toward us
E. Away from us
12
911 A particle of charge ( boldsymbol{q}=mathbf{1 6} times mathbf{1 0}^{-18} mathbf{C} )
moving with ( 10 m s^{-1} ) along ( x- ) axis
enter a magnetic field of induction ( boldsymbol{B} ) along the ( y- ) axis and an electric field ( 10^{4} mathrm{Vm}^{-1} ) along negative ( z- ) direction. If
the particle continues to move along ( x- ) axis then the strength of magnetic field is
( mathbf{A} cdot 10^{5} mathrm{Wbm}^{-2} )
B. ( 10^{16} mathrm{wbm}^{-2} )
c. ( 10^{-3} mathrm{wbm}^{-2} )
D. ( 10^{3} mathrm{wbm}^{-2} )
12
912 Find the magnetic moment vector of the
loop
A ( cdot(0.1 hat{i}+0.05 hat{j}-0.05 hat{k}) A m^{2} )
B . ( (0.1 hat{i}+0.05 hat{j}+0.05 hat{k}) A m^{2} )
C ( cdot(0.1 hat{i}-0.05 hat{j}+0.05 hat{k}) A m^{2} )
D. ( (0.1 hat{i}-0.05 hat{j}-0.05 hat{k}) A m^{2} )
12
913 The magnetic field at the center of the
circular loop as shown in figure, when a
single wire is bent to form a circular
loop and also extends to form straight sections, is :
( ^{text {A }} cdot frac{mu_{0} I}{2 R} odot )
( ^{text {В }} cdot frac{mu_{0} I}{2 R}left(1+frac{1}{pi sqrt{2}}right) odot )
c. ( frac{mu_{0} I}{2 R}left(1-frac{1}{pi sqrt{2}}right) otimes )
( stackrel{mathrm{D}}{frac{mu_{0}}{R}}left(1-frac{1}{pi sqrt{2}}right) otimes )
12
914 toppr
Q Type your question.
point of time direction of magnetic field
is reversed then which of the following path is/are possible for the charged
particle. Here ( boldsymbol{v}_{0} ) and ( boldsymbol{B}_{0} ) are positive
constants.
( A )
в.
( c )
D. None of the abç
12
915 A spring of spring constant ( boldsymbol{K} ) is fixed at
one end has a small block of mass ( m )
and charge ( q ) is attached at the other
end. The block rests over a smooth
horizontal surface. A uniform and
constant magnetic field ( B ) exists
normal to the plane of the paper as
shown in the figure. An electric field ( overrightarrow{boldsymbol{E}}=boldsymbol{E}_{0} hat{boldsymbol{i}}left(boldsymbol{E}_{0} text { is a positive constant }right) ) is
switched on at ( t=0 ) sec. The block
moves on the horizontal surface without
ever lifting off the surface. Where is the normal reaction acting on the block
maximum?
12
916 Derive the formula ( frac{boldsymbol{F}}{boldsymbol{l}}=frac{boldsymbol{mu}_{o}}{mathbf{2} boldsymbol{pi}} cdot frac{boldsymbol{i}_{1} boldsymbol{i}_{2}}{boldsymbol{r}} ) as
the force per unit length between two parallel wires each of length I meter,
carrying currents ( i_{1} ) and ( i_{2} ) amperes and separated by a distance r meters. Define ampere with the help of this formula.
12
917 An electron moves at right angle to a
magnetic field of ( 1.5 times 10^{-2} T ) with a
speed of ( 6 times 10^{7} m / s . ) If the specific
charge on the electron is ( 1.7 times ) ( 10^{11} C / k g, ) the radius of the circular
path will be
A . ( 2.9 mathrm{cm} )
B. 3.9 ( mathrm{cm} )
c. ( 2.35 mathrm{cm} )
D. ( 2 mathrm{cm} )
12
918 ( vec{B}=-(0.31 T) hat{i} ) what will be the angle between ( hat{text { iand }} ) B. (length of wire is 0.01m)
A .
в. ( (0.01085 N) hat{k} )
c. ( (-0.01085 N) hat{k} )
D. ( (0.01085 N) hat{i} )
12
919 What reading would you expect of a square-wave current, switching rapidly between ( +0.5 A ) and ( -0.5 A, ) when
passed through an ac ammeter?
( mathbf{A} cdot mathbf{0} )
B. ( 0.5 A )
c. 0.25
D. ( 1.0 A )
12
920 A long straight wire is carrying current
( l_{1}=frac{2}{5} A ) along ( +z ) direction. The ( x-y )
plane contains a closed circular loop carrying and not encircling the straight wire, then the force (in newton) on the
loop will be ?
(radius of the circular loop ( left.boldsymbol{R}=frac{3}{4} boldsymbol{m}right) )
A . 0
B. 2
( c cdot-1 )
D.
12
921 Electric current is passed through a straight conductor passing through the center of a piece of cardboard.Some iron fillings are sprinkled on the cardboard and tapped.The iron fillings
around the conductor
A. Settle as parallel lines
B. Settle as circles
c. settle at one point
D. Do not acquire any regular pattern
12
922 Unit of magnetic induction ( B ) is :
A ( frac{N}{A m} )
в. ( frac{N A}{m} )
c. ( frac{N m}{A} )
D. ( frac{N}{A} )
12
923 A range of galavanometer is ‘ ( V ) ‘, when
( 50 Omega ) resistance is connected in series.
Its range gets doubled when ( 500 Omega ) resistance is connected in series.
Galvanometer resistance is
( mathbf{A} cdot 100 Omega )
в. 200Omega
c. ( 300 Omega )
D. ( 400 Omega )
12
924 The magnetic field due to a current carrying circular loop of radius ( 3 mathrm{cm} ) at a point on the axis at a distance of ( 4 mathrm{cm} )
from the centre is ( 54 mu ) T. What will be
its value at the centre of the loop?
A. 125 и ( T )
в. ( 150 mu T )
c. ( 250 mu T )
D. ( 75 mu T )
12
925 The segment ( A B ) of wire carrying current
( I_{1} ) is placed perpendicular to a long
straight wire carrying current ( boldsymbol{I}_{2} ) as
shown in figure.The magnitude of force experienced by the straight wire ( A B ) is
A ( cdot frac{mu_{o} I_{1} I_{2}}{2 pi} 1 n 3 )
В. ( frac{mu_{o} I_{1} I_{2}}{2 pi} 1 n 2 )
c. ( frac{2 mu_{o} I_{1} I_{2}}{2 pi} )
D. ( frac{mu_{o} I_{1} I_{2}}{2 pi} )
12
926 Compare Biot-Savart law with Coulomb’s law for electrostatic field. 12
927 Seema’s uncle was advised by his doctor to have an MRI
(Magnetic Resonance Imaging) scan of his brain. Her uncle felt it to be
expensive and wanted to postpone it. When Seema learnt about this, she took
the help of her family and
also approached the doctor, who also offered a substantial discount. She
then convinced her uncle to undergo the
test to enable the doctor to know
the condition of his brain. The
information thus obtained greatly helped the doctor to treat him properly. Based on the above paragraph, answer the question. Assuming that MRI test was performed using a magnetic field of ( 0.1 mathrm{T} ), find the minimum and maximum values of
the force that the magnetic field could exert on a proton moving with a speed of
( mathbf{1 0}^{4} mathbf{m} / mathbf{s} )

Given charge of proton ( =1.6 times 10^{-19} mathrm{C} )

12
928 There are two wires ( a b ) and ( c d ) in a
vertical plane as shown in figure.Direction of current in wire ( a b ) is
rightwards.Choose the correct options
This question has multiple correct options
A. If wire ( a b ) is fixed then wie ( c d ) can be kept in equilibrium by the current in ( c d ) in leftward direction
B. Equilibrium of wie ( c d ) will be stable equilibrium
C. If wire ( c d ) is fixed,then wire ( a b ) can be kept in equilibrium by flowing current in ( c d ) in rightward direction
D. Equilibrium of wire ( a b ) will be stable equilibrium
12
929 A moving coil galvanometer has a coil of area ( A ) and number of turns ( N . A )
magnetic field B is applied on it. The torque acting on it is given by ( boldsymbol{tau}=boldsymbol{k} boldsymbol{i} )
where i is current through the coil. If moment of inertia of the coil is I about
the axis of rotation.
If the value of torsional constant if
current ( i_{0} ) produces angular deflection of ( pi / 2 ) rad is ( C=frac{x N B A i_{0}}{pi} . ) Find ( x )
12
930 The correct Biot-Savart law in vector
form is?
( ^{mathbf{A}} cdot d vec{B}=frac{mu_{0}}{4 pi} frac{I(d vec{l} times vec{r})}{r^{2}} )
в. ( d vec{B}=frac{mu_{0}}{4 pi} frac{I(d vec{l} times vec{r})}{r^{3}} )
( ^{mathrm{c}} cdot d vec{B}=frac{mu_{0}}{4 pi} frac{I d bar{l}}{r^{2}} )
D ( cdot d vec{B}=frac{mu_{0}}{4 pi} cdot frac{I d vec{l}}{r^{3}} )
12
931 A long straight wire of radius R carries current ( i . ) The magnetic field inside the wire at distance ( r ) from its centre is
expresses as:
( mathbf{A} cdotleft(frac{mu_{0} i}{pi R^{2}}right) cdot r )
в. ( left(frac{2 mu_{0} i}{pi R^{2}}right) cdot pi )
( ^{text {c. }}left(frac{mu_{0} i}{2 pi R^{2}}right) cdot r )
D. ( left(frac{mu_{0} i}{2 pi R}right) cdot )
12
932 A small coil of N turns has an area A
and a current i flows through it. The magnetic dipole moment of the coil will
be
( A cdot ) i ( N A )
B . ( i^{2} mathrm{NA} )
( c cdot i N^{2} A )
D. iN/A
12
933 A uniform electric field ‘E’ is directed
towards positive X-axis. If at ( X=0, ) the electric potential is zero, then the
potential at ( boldsymbol{X}=+boldsymbol{X}_{0}, ) would be
A ( cdot frac{E}{X_{0}} )
в. ( frac{-E}{X_{0}} )
c. ( -E X_{0} )
D. ( E X_{0} )
12
934 The force experienced by a current carrying conductor placed in a magnetic field is largest when magnetic feild,current and length of conducter is more
Type 1 for true and 0 for false
12
935 When a steel core is placed in a
solenoid, it acts like an electromagnet.
A. True
B. False
12
936 A moving-coil galvanometer has its coil of 24 turns and ( 12 Omega ) resistance. By how much the number of turns should be
increased so that the current sensitivity of the galvanometer increases by ( 25 % ? )
If, in doing so, the resistance of the coil
increases to ( 20 Omega ), what will be the effect on the voltage-sensitivity of the galvanometer?
12
937 Assertion
The magnetic field at the ends of a very long current carrying solenoid is half of that at the center.
Reason
If the solenoid is sufficiently long, the field within it is uniform.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
938 A circular coil of 100 turns has an
effective radius of ( 0.05 mathrm{m} ) and carries a
current of 0.1 A. How much work is
required to turn it in an external magnetic field of ( 1.5 W b m^{-2} ) through
( 180^{circ} ) about an axis perpendicular to the magnetic field?
12
939 Two parallel wires in free space are ( 10 mathrm{cm} ) apart and each carries a current
of ( 10 A ) in the same direction. The force
exerted by one wire on other per metre of length of the wire is
A ( cdot 2 times 10^{-6} N )
B . ( 2 times 10^{-4} N )
c. ( 2 times 10^{-3} N )
D ( cdot 2 times 10^{-2} N )
12
940 Phosphor-Bronze wire is used for suspension in a moving coil galvanometer because it has.
A. High conductivity
B. High resistivity
c. Large couple per unit twist
D. Small couple per unit twise
12
941 State the rule to determine the
direction of a Magnetic field produced around a straight conductor carrying
current
12
942 Which rule determines the direction of
force experienced by a current Carrying straight conductor placed in a magnetic field which is perpendicular to it.
A. Maxwell right hand grip rule
B. Fleming’s left hand rule
C. Fleming’s right hand rulel
D. None
12
943 When a permanent magnet is moved towards a coil, current is induced in the
coil by faraday’s law. What is the source
of energy associated with the current produced?
12
944 Explain with neat diagram the principle, construction and working of a cyclotron. 12
945 A moving charge can produce a magnetic field. How does a current loop behaves like a magnetic dipole? 12
946 A small ball of volume ( V ) made of
paramagnetic with susceptibility ( chi ) was slowly displaced along the axis of a current-carrying coil from the point where the magnetic induction equals ( B )
out to the region where the magnetic field is practically absent. What amount of work was performed during this process?
12
947 Write Ampere circuital law in
mathematical form. Derive an
expression of magnetic field at the axis of a current carrying long solenoid. Draw necessary diagram.
12
948 (a)Draw a schematic sketch of a
cyclotron. Explain clearly the role of crossed electric and magnetic field in accelerating the charge. Hence derive the expression for the kinetic energy
acquired by the particles.
(b) An ( alpha ) – particle and a photon are released from the centre of the cyclotron
and made to accelerate:
(i) Can both be accelerated at the same
cyclotron frequency? Give reason to justify your answer
(ii) When they are accelerated in turn,
which of the two will have higher velocity at the exit slit.
12
949 A positively charged particle of ( 2.0 C ) moves upward into an area where both a magnetic field of the magnitude
( 4.0 times 10^{-4} T ) and an electric field of
the magnitude ( 0.1 N / C ) are acting. Find out the velocity at which particle must move if it is not deflected when it enters
this area?
A ( cdot 4.0 times 10^{-3} mathrm{m} / mathrm{s} )
B. ( 125 mathrm{m} / mathrm{s} )
c. ( 250 m / s )
D. ( 500 m / s )
E. The particle will be deflected to the left regardless of ts velocity
12
950 A proton is moving with velocity ( 10^{4} m / s ) parallel to the magnetic field of
intensity 5 tesla.The force on the proton
is
A. ( 8 times 10^{15} N )
B . ( 10^{4} N )
c. ( 1.6 times 10^{-19} N )
D. zero
12
951 Figure shows a conducting loop ( A B C D A ) placed in a uniform magnetic field (strength ( B ) ) perpendicular to its plane. The part ( A B C ) is the (three-
fourth) portion of the square of side Iength ( l ). The part ( A D C ) is a circular arc
of radius ( R ). The points ( A ) and ( C ) are
connected to a battery which supplies a current ( I ) to the circuit. The magnetic force on the loop due to the field ( B ) is :
A . zero
В. ( B I l )
c. ( 2 B I R )
D.
[
frac{B I l R}{I+R}
]
12
952 Under what condition is the force acting
on a charge moving through a uniform magnetic field minimum?
12
953 A specimen of iron of permeability ( 8 times )
( 10^{-3} ) Weber/A m is placed in a
magnetic field of strength ( 160 mathrm{A} / mathrm{m} ) Magnetic induction in this iron is:
( mathbf{A} cdot 0.8 W b / m^{2} )
B. ( 5 times 10^{5} mathrm{Wb} / mathrm{m}^{2} )
c. ( 1.28 W b / m^{2} )
D . ( 20 times W b / m^{2} )
12
954 A galvanometer in a circuit:
A. measures current
B. measures voltage
C. measures emf
D. indicates flow of current
12
955 f a current lis flowing in a loop of
radius r as shown in adjoining figure,
then the magnetic field induction at the
centre 0 will be
A. zero
в. ( frac{mu_{0} I theta}{4 pi r} )
c. ( frac{mu_{0} I sin theta}{4 pi r} )
D. ( frac{2 mu_{0} I sin theta}{4 pi r^{2}} )
12
956 Cathode rays gain kinetic energy when accelerated by an electric field. If they are subjected to a uniform magnetic field, then their
A. energy increases
B. momentum increases
c. energy and momentum decrease
D. energy and momentum remain unaffected
12
957 The leakage flux of a toroid is less
because
A. It is asymmetrical
B. It has an open-loop core
c. It is symmetrical.
D. It has a straight core
12
958 Write the formula of Biot-Sevart law in
vector form. Obtain an expression of magnetic field on the axis of a current
carrying circular loop. Draw necessary diagram.
12
959 A moving coil galvanometer A has 100
turns and resistance ( 10 Omega ). Another
galvanometer B has 50 turns and 5 ( Omega )
The other quantities are same in both the cases. Then the voltage sensitivity of :
A. A is greater than that of
B. B is greater than that of
c. ( A ) and ( B ) is same
D. Cannot be compared
12
960 The intensity of magnetic induction field at the centre of a single turn circular coil of radius ( 5 mathrm{cm} ) carrying of
0.9 A current is:
A . ( 36 pi times 10^{-7} mathrm{T} )
В . ( 9 pi times 10^{-7} T )
( mathbf{c} cdot 36 pi times 10^{-6} T )
D. ( 9 pi times 10^{-6} T )
12
961 A long wire carries a steady current. IT
is bent into a circle of one turn and the
magnetic field at the centre of the coil
is ( B ). It is then bent into a circular loop
of ( n ) turns. The magnetic field at the centre of the coil will be:
( mathbf{A} cdot n B )
B . ( n^{2} B )
( c cdot 2 n B )
D. ( 2 n^{2} B )
12
962 What is the main reason for using a
solenoid instead of a straight wire to produce magnetic field?
12
963 The coil in a MCG has an area of ( 4 mathrm{cm}^{2} )
and 500 turns. The intensity of magnetic induction is 2T. When a
current of ( 10^{-4} ) A is passed through it,
the deflection is ( 20^{0} ). The couple per
unit twist is (N-m)
A. ( 3 times 10^{-6} )
B. ( 2 times 10^{-6} )
( mathbf{c} cdot 4 times 10^{-6} )
D. ( 5 times 10^{-6} )
12
964 The magnetic induction at 0 due to a current in conductor shaped as shown
in figure is:
A ( cdot frac{mu_{0} i}{4 pi}left[frac{3 pi}{2 a}+frac{sqrt{2}}{b}right] )
В ( cdot frac{mu_{0} i}{4 pi}left[frac{3 pi}{4 a}-frac{sqrt{2}}{b}right] )
( ^{text {c. }} cdot frac{mu_{0} i}{2 pi}left[frac{3 pi}{4 a}-frac{1}{sqrt{2} b}right] )
D. ( frac{mu_{0}}{2 pi}left[frac{1}{a}+frac{1}{b}right. )
12
965 On connecting a shunt of ( 12 Omega, ) the deflection of galvanometer reduces from 50 to 20 divisions. Calculate
resistance of galvanometer.
12
966 The magnetic field generated along the axis of a solenoid is proportional to:
A. its length
B. square of current flowing in it
c. number of turns per unit length in it
D. reciprocal of its radius
12
967 Calculate magnetic flux density of the magnetic field at the centre of a
circular coil of 50 tunrs, having radius of ( 0.5 mathrm{m} ) and carrying a current of ( 5 mathrm{A} )
12
968 What is the name given to a cylindrical
coil whose diameter is less in
comparison to its length?
12
969 A voltmeter has a resistance of ( G ) ohms
and range ( V ) volts. The value of
resistance required in series to convert
it into voltmeter of range ( n V ) is
A ( . n G )
в. ( G / n )
c. ( G /(n-1) )
D. ( (n-1) G )
12
970 toppr ( t )
Q Type your question
of the forces exerted on the wires?
( A )
в.
( c )
D.
12
971 Two long straight wires are set parallel
to each other at separation ( r ) and each
carries a current ( i ) in the same
direction. The strength of the magnetic field at any point midway between the two wires is
A ( cdot frac{mu_{0} i}{pi r} )
в. ( frac{2 mu_{0}}{pi r} )
c. ( frac{mu_{0} i}{2 pi r} )
D. zero
12
972 A solenoid is ( 2.0 mathrm{m} ) long and ( 3.0 mathrm{cm} ) in diameter. It has 5 layers of winding of 1000 turns each and carries a current of
5.0 A. What is the magnetic field at its centre?
A ( cdot 1.5 times 10^{-3} T )
в. ( 1.5 times 10^{-2} T )
c. ( 1.5 times 10^{-4} T )
D. ( 2.5 times 10^{-2} T )
12
973 A metallic rod ( C D ) rests on a thick
metallic wire ( P Q R S ) with arms ( P Q ) and
( R S ) parallel to each other, at a distance
( l=40 mathrm{cm}, ) as shown in following figure.
A uniform magnetic field ( B=0.1 T )
acts perpendicular to the plane of this paper, pointing inwards (i.e., aways
from the reader). The rod is now made to
slide towards right, with a constant
velocity of ( boldsymbol{v}=mathbf{5 . 0} boldsymbol{m} boldsymbol{s}^{-1} )
How much emf is induced between the
two ends of the rod ( C D ? )
12
974 A current i, indicated by the crosses in
figure, is established in a strip of
copper of height ( h ) and width ( w . A )
uniform field of magnetic induction B is
applied at right angle to the strip.

Calculate voltage V necessary between
two sides of the conductor in order to
create this field E. Between which sides
of the conductor would this voltage have
to be applied?
A ( cdot 5 times 10^{-6} ) Top and Bottom, with top +ve charge and
bottom -ve charge
B. ( 5 times 10^{-6} ) Top and Bottom, with top -ve charge and
bottom +ve charge
( mathbf{c} cdot 5 times 10^{-6} ) Any
D. None of the above

12
975 A positively charged particle of charge 1
C and mass 40 g, is revolving along a circle of radius ( 40 mathrm{cm} ) with velocity
( 5 mathrm{m} / mathrm{s} ) in a uniform magnetic field with centre at origin 0 in ( x ) -y plane ( . A t t=0 ) the particle was at ( (0,0.4 mathrm{m}, 0) ) and velocity was directed along positive ( x ) direction.Another particle having charge ( 1 mathrm{C} ) and mass ( 10 mathrm{g} ) moving uniformly parallel to z-direction with velocity ( frac{40}{pi} m / s ) collides with revolving particle at ( t=0 ) and gets stuck with it. Neglecting gravitational force and coulombian force,calculate ( x, y ) and ( z ) coordinates of the combined particle at ( t=frac{pi}{40} sec )
12
976 A long wire bent as shown in figure
carries current ( I . ) If the radius of the
semicircular portion is ( a ), the magnetic
field at center ( C ) is:
A ( cdot frac{mu_{0} I}{4} )
B. ( frac{mu_{0} I}{4 pi a} sqrt{pi^{2}+4} )
c. ( frac{mu_{0} I}{4 a}+frac{mu_{0} I}{4 pi a} )
D. ( frac{mu_{0} I}{4 pi a} sqrt{pi^{2}-4} )
12
977 An infinitely long straight conductor is
bent into shape as shown in figure. It
carries a current I A. and the radius of
circular loop is r metre. Then the
magnetic induction at the centre of the
circular loop is:
( A )
B. ( frac{mu_{0}}{pi r_{0}} )
c. ( frac{mu_{0} i}{2 pi r}(pi+1) )
D ( cdot frac{mu_{0} i}{2 pi r}(pi-1) )
12
978 If a shunt of ( frac{1}{10} t h ) of the coil resistance is applied to a moving coil galvanometer, its sensitivity becomes
A. 10 fold
в. ( frac{1}{10} ) fold
c. 11 fold
D. ( frac{1}{11} ) fold
12
979 The sensitivity of a galvanometer will increase if
A. radius of coil is increased
B. number of turns in coil is decreased
c. radius of coil is decreased
D. a strong field is used
12
980 A particle of mass ( mathrm{M} ) and charge ( mathrm{Q} ) moving with velocity ( vec{v} ) describe a circular path of radius R when subjected to a uniform transverse magnetic field of induction B. The work done by the field when the particle completes one full circle is
( ^{mathbf{A}} cdotleft(frac{M v^{2}}{R}right)^{2 pi R} )
в. zero
с. ( B Q 2 pi R )
D. ( B Q v 2 pi R )
12
981 In an atom, electrons revolve around the
nucleus. This gives rise to
A. only electric field
B. only magnetic field
c. both electric and magnetic fields
D. none of the above
12
982 In a cyclotron, magnetic field of ( 1.4 W b / m^{2} ) is used. To accelerate
protons, how rapidly should the electric field between the Dees he reversed?
( left(boldsymbol{pi}=mathbf{3 . 1 4 2}, boldsymbol{M} boldsymbol{p}=mathbf{1 . 6 7} times mathbf{1 0}^{-mathbf{2 7}} mathbf{k g}, boldsymbol{e}=right. )
( left.mathbf{1 . 6} times mathbf{1 0}^{-mathbf{1 9}} mathbf{C}right) )
12
983 toppr
( Q )
electrostatic field is maintained in
a direction normal to the common axis
of the coils. A narrow beam of (single
species) charged particles al
accelerated through ( 15 k V ) enters this region in a direction perpendicular to both the axis of the coils and the
electrostatic field. If the beam remains
undeflected when the electrostatic field
is ( 9.0 times 10^{-5} V m^{-1}, ) make a simple
guess as to what the beam contains. Why is the answer not unique?

Consider two parallel co-axial circular coils of equal radius ( R ), and number of turns ( N, ) carrying equal currents in the same direction, and separated by a distance ( R ) Show that the field on the
axis around the mid-point between the coils is uniform over a distance that is
small as compared to ( R ), and is given by, ( boldsymbol{B}=mathbf{0 . 7 2} frac{boldsymbol{mu}_{0} boldsymbol{N I}}{boldsymbol{R}} )
[Such an arrangement to produce a nearly uniform magnetic field over a small region is known as Helmholtz coils ( ] )

12
984 A charged particle moves in a circular path in a uniform magnetic field.If the speed is reduced then its time period will
A. increase
B. decrease
c. remain same
D. None of these
12
985 A circular loop of radius R carrying a current lis placed in a uniform magnetic field B perpendicular to the
loop. The force on the loop is:
A ( .2 pi R I B )
В. ( 2 pi R I^{2} B^{3} )
( mathbf{c} cdot pi R^{2} I B )
D. zero
12
986 A galvanometer of resistance, ( G ) is
shunted by a resistance ( S ) ohm. To keep
the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is
A ( cdot frac{S^{2}}{(S+G)} )
B. ( frac{S G}{(S+G)} )
c. ( frac{G^{2}}{(S+G)} )
D. ( frac{G}{(S+G)} )
12
987 A wire of length L metre carrying current ampere is bent in the form of a circle.
What is the magnitude of magnetic
dipole moment?
A ( cdot I L^{2} / 4 pi )
B . ( I^{2} L^{2} / 4 pi )
c. ( I^{2} L / 8 pi )
D. ( I L^{2} / 8 pi )
12
988 Two current carrying loops of same area but of different materials have same
current flowing in them in anticlockwise direction. if a magnetic field is applied in upward direction then potential energy of loop 1 and loop 2 will
always be:
A. Different
B. Equal
c. can be different or equal depend upon material
D. Can’t say
12
989 Find ampere force acting on the frame 12
990 An arc of a circle of radius ( R ) subtends
an angle ( frac{pi}{2} ) at the centre. It carries a
current ( i . ) The magnetic field at the centre will :
A ( cdot frac{mu_{0} i}{2 R} )
в. ( frac{mu_{0} i}{8 R} )
c. ( frac{mu_{0} i}{4 R} )
D. ( frac{mu_{0} i}{5 R} )
12
991 A ( 2 mathrm{m} ) long conductor, carries a current
of ( 50 mathrm{A} ) at a magnetic field of ( 10^{-1} ) T. The force on the conductor is:
A . 10 N
B. 100 N
( c cdot 1000 N )
D. ( 10,000 mathrm{N} )
12
992 A solenoid of length ( 0.4 mathrm{m}, ) having 500 turns and 3 A current flows through it. A coil of radius ( 0.01 mathrm{m} ) and have 10 turns
and carries current of 0.4 A has to
placed such that its axis is perpendicular to the axis of solenoid then torque on coil will be
A ( cdot 5.92 times 10^{-7} N cdot m )
В. ( 5.92 times 10^{-5} mathrm{N} . mathrm{m} )
c. ( 5.92 times 10^{-4} N . m )
D. ( 5.92 times 10^{-3} N . m )
12
993 The charge is moving along the direction of magnetic field. Then force acting on it is
A. Maximum
B. qvB
c. zero
D. Bil
12
994 A circular coil of magnetic moment
( 0.355 J T^{-1} ) rests with its plane normal
to an external field of magnitude ( 5.0 times )
( 10^{-2} mathrm{T} . ) The coil is free to turn about an
axis in its plane perpendicular to the field direction. When the coil is turned
slightly and released, it oscillates about its stable equilibrium with a frequency
of ( 2 mathrm{Hz} ). The moment of inertia of the coil
about its axis of rotation is?
A ( cdot 1.13 times 10^{-1} mathrm{kg} mathrm{m}^{2} )
B . ( 1.13 times 10^{-2} ) kg ( m^{2} )
C ( cdot 1.13 times 10^{-3} mathrm{kg} mathrm{m}^{2} )
D. ( 1.13 times 10^{-4} mathrm{kg} mathrm{m}^{2} )
12
995 The sensitivity of a moving coil galvanometer increases with the decrease in
A. number of turns
B. area of coil
c. magnetic field
D. couple per unit twist
12
996 ( boldsymbol{x}=mathbf{0 . 5 0 0 m}, boldsymbol{y}=mathbf{0}, boldsymbol{z}=mathbf{0} ) 12
997 I ne rectangular wıre trame, shown In
the figure has a width d, mass ( m )
resistance ( R ) and a large length. ( A ) uniform magnetic field B exists to the left of the frame. A constant force ( F )
starts pushing the frame into the
magnetic field at ( t=0 )
(a)Find the acceleration of the frame
when its speed has increased to
(b how that after some time the frame
will move with a constant velocity till the whole frame enters into the
magnetic field. Find the velocity ( v_{0} )
(c) Show that the velocity at time t is given byv ( =boldsymbol{v}_{0}left(mathbf{1}-boldsymbol{e}^{frac{-F t}{m v_{0}}}right) )
[
begin{array}{ll}
x & x \
x & x \
x & x \
x & x \
x & x
end{array}
]
12
998 Three ions ( H^{+}, H e^{+} ) and ( O^{+2} ) having
same kinetic energy pass through a region in which there is a unit magnetic field perpendicular to their velocity,
then
A ( cdot H^{+} ) will be least deflected
B. ( H e^{+} ) and ( O^{+2} ) will be deflected equally
c. ( O^{+2} ) will be deflected most
D. All will be deflected equally
12
999 1)
( I, ) is placed in a horizontal plane near a
long straight conductor carrying steady
current ( I_{1} ) at a distance ( d ) from the
conductor as shown in figure. The loop
will experience
A. A net repulsive force away from the conductor
B. A net torque acting upward perpendicular to the horizontal plane
c. A net torque acting downward normal to the horizontal plane
D. A net attractive force towards the conductor
12
1000 A moving coil galvanometer is based on
the
A. heating effect of current
B. magnetic effect of current
c. chemical effect of current
D. peltier effect of current
12
1001 A charged particle ( A ) of charge ( q=2 C )
has velocity ( boldsymbol{v}=mathbf{1 0 0} boldsymbol{m} / boldsymbol{s} . ) When it
passes through point ( A ) and has
velocity in the direction shown, the strength of magnetic field at point ( B )
due to this moving charge is ( (r=2 m) )
A ( .2 .5 mu T )
B. ( 5.0 mu T )
c. ( 2.0 mu T )
D. none of these
12
1002 Assertion
A galvanometer can be used as a voltmeter to measure the voltage
across a given section of the circuit.
Reason
For this it must be connected in parallel
with that section of the circuit.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
1003 A copper wire of diameter ( 1.6 m m )
carries a current of ( 20 A ). Find the
maximum magnitude of the magnetic field ( vec{B} ) due to this current.
12
1004 If an electron and a proton having same momenta enter perpendicular to a magnetic field, then :
A. curved path of electron and proton will be same (ignoring the sense of revolution)
B. They will move undeflected
c. curved path of electron is more curved than that of the proton
D. Path of proton is more curved
12
1005 A long solenoid has 200 turns per ( mathrm{cm} )
and carries a current ( i . ) The magnetic field at its centre is ( 6.28 times ) ( 10^{-2} W b / m^{2} ) Another long solenoid has
100 turns per cm and it carries a
current ( i / 3 . ) The value of the magnetic field at its centre
is :
A ( cdot 1.05 times 10^{-4} W b / m^{2} )
B . ( 1.05 times 10^{-2} mathrm{Wb} / mathrm{m}^{2} )
c. ( 1.05 times 10^{-5} mathrm{Wb} / mathrm{m}^{2} )
D. ( 1.05 times 10^{-3} mathrm{Wb} / mathrm{m}^{2} )
12
1006 Two current-carrying parallel conductors are shown in the figure. The
magnitude and nature of force acting between them per unit length will be :
A ( cdot 8 times 10^{-8} N / m, ) attractive
B. ( 3.2 times 10^{-5} N / m ), repulsive
c. ( 3.2 times 10^{-5} N / m ), attractive
D. ( 8 times 10^{-8} N / m ), repulsive
12
1007 The wires which connect the battery of
an automobile to its starting motor
carry a current of 300 A (for a short
time). What is the force per unit length
between the wires if they are ( 70 mathrm{cm} ) long
and ( 1.5 mathrm{cm} ) apart? Is the force attractive or repulsive?
12
1008 Nu Which
pictured, moving northeast through a
magnetic field that points straight up. What is the direction of the force on the
negatively charged particle at the
moment it is pictured?
North
west
( – )
East
South
A. Northeast
B. Southeast
c. Southwest
D. Northwest
E. Up
12
1009 Evaluate the magnitude and direction
of magnetic field at point ( boldsymbol{O} )
A ( cdot frac{3 mu_{0} i}{8 a}, ) с
в. ( frac{mu_{0} i}{2 sqrt{2} b}, ) с
с. ( frac{3 mu_{0} i}{8 a}+frac{mu_{0} i}{2 sqrt{2} b}, ) с
D. ( frac{3 mu_{0} i}{8 a}+frac{mu_{0} i}{2 sqrt{2} b}, otimes )
12
1010 Assertion
A proton and an alpha particle having the same kinetic energy are moving in circular paths in a uniform magnetic field. The radii of their circular paths will be equal
Reason Any two charged particles having equal kinetic energies and entering a region of uniform magnetic field ( vec{B} ) in a direction perpendicular to ( vec{B}, ) will describe circular trajectories of equal radii.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
1011 If the current sensitivity of a galvanometer is doubled, then its voltage sensitivity will be
A. doubled
B. halvedd
c. unchanged
D. four times
12
1012 A positively charged croquet ball rolls at
( 4.0 m / s ) northward through a ( 2.00 T )
magnetic field which points westward.
If the charge on the croquet ball is ( 1.0 C )
how much force acts on the croquet ball
due to the magnetic field and in what
direction?
A. Amount of Force ( -2.00 N ), Direction of Force – up
B. Amount of Force ( -8.00 N ), Direction of Force – south
C. Amount of Force ( -8.00 N ), Direction of Force – down
D. Amount of Force ( -0.500 N ), Direction of Force – up
E. Amount of Force ( -8.00 N ), Direction of Force – up
12
1013 The wire shown in figure carries a
current of ( 40 A . ) If ( r=3.14 c m ) the
magnetic field at point p will be :
A ( .1 .6 times 10^{-3} T )
В. ( 3.2 times 10^{-3} T )
c. ( 6 times 10^{-4} T )
D . ( 4.8 times 10^{-3} T )
12
1014 A cyclotron’s oscillator frequency is 10
MHz and the operating magnetic field is ( 0.66 mathrm{T} . ) If the radius of its dees is ( 60 mathrm{cm} )
then the kinetic energy of the proton beam produced by the accelerator is?
( mathbf{A} cdot 9 mathrm{MeV} )
B. 10 Mev
c. 7 Mev
D. 11 Mev
12
1015 Why don’t two magnetic lines of force intersect with each other? 12
1016 A particle having mass ( m ) and charge ( q ) is released from the origin in a region in which electric field and magnetic fields are given by ( vec{B}=-B_{0} hat{j} ) and ( vec{E}=E_{0} hat{k} )
Find the speed of the particle as a
function of its ( z- ) coordinate.
A ( cdot sqrt{frac{q E z}{m}} )
B. ( sqrt{frac{2(q v B+q E) z}{m}} )
D. ( sqrt{frac{2 q E z}{m}} )
12
1017 The area of the coil in a moving coil
galvanometer is ( 80 mathrm{cm}^{2} ) and it has 200 turns. The magnetic induction of the radial field is ( 0.2 mathrm{T} ) and the couple per unit twist of the suspension wire is ( 2 x )
( 10^{-6} N m ) per degree. If the deflection is
4, the current passing through it is
( A cdot 0.25 mathrm{m} mathrm{A} )
в. 2.5 ( mathrm{m} ) А
c. ( 0.025 mathrm{mA} )
D. 250 mA
12
1018 Figure shows a square current-carrying
loop ( A B C D ) of side ( 2 m ) and current
( boldsymbol{I}=frac{1}{2} boldsymbol{A} . ) The magnetic moment ( overrightarrow{boldsymbol{M}} ) of
the loop is:
A ( cdot(hat{i}-sqrt{3} hat{k}) A-m^{2} )
( mathbf{B} cdot(hat{j}-hat{k}) A-m^{2} )
c. ( (sqrt{3} hat{i}-hat{k}) A-m^{2} )
D. ( (hat{i}-hat{k}) A-m^{2} )
12
1019 A solenoid ( 1.5 mathrm{m} ) long and ( 4.0 mathrm{cm} ) in diameter possesses 10 turns/cm. current of 5 A is flowing through it. Then the magnetic induction (i) inside and
(ii) at one end on the axis of solenoid
are respectively
A ( cdot 2 pi times 10^{-3} T, pi times 10^{-3} T )
В . ( 3 pi times 10^{3} T, 1.5 pi times 10^{3} T )
c. ( 0.5 pi times 10^{3} 10^{3} T, 4 pi times 10^{3} T )
D. ( 4 pi times 10^{3} T, 2 pi times 10^{3} )
12
1020 The magnitude of force experienced by
the arc ( M N ) is
A. zero
B. ( frac{mu_{0} V I_{0}}{pi R b} )
C ( frac{mu_{0} V I_{0}}{2 pi R b} )
D. none of these
12
1021 The magnetic moment ( (mu) ) of a revolvng
electron around the nucleus varies with
principle quantum number n as
( mathbf{A} cdot mu propto n )
в. ( mu propto 1 / n )
c. ( mu propto n^{2} )
D. ( mu propto 1 / n^{2} )
12
1022 Two infinite long wires, each carrying
current ( I, ) are lying along ( x ) -axis and ( y )
axis, respectively. ( A ) charged particle,
having a charge ( q ) and mass ( m ), is
projected with a velocity ( u ) along the
straight line ( O P . ) The path of the
particle is (neglect gravity) a:
A. straight line
B. circle
c. helix
D. cycloid
12
1023 A small circular loop of conducting wire
has radius ( a ) and carries current ( I ). It is
placed in a uniform magnetic field ( boldsymbol{B} ) perpendicular to its plane such that
when rotated slightly about its
diameter and replaced, it starts performing simple harmonic motion of time period ( T . ) If the mass of the loop is
( m ) then:
( ^{mathbf{A}} cdot_{T}=sqrt{frac{2 m}{I B}} )
в. ( T=sqrt{frac{pi m}{I B}} )
( ^{mathrm{c}} cdot T=sqrt{frac{2 pi m}{I B}} )
D ( cdot T=sqrt{frac{pi m}{2 I B}} )
12
1024 The magnetic field at the center of the
coil of radius ( r ) and carrying a current ( I )
as shown in the figure is : (the wires crossing at ( P ) are insulated from each
other)
A ( cdot frac{mu_{0}}{4 pi} frac{2 I}{r}(1+pi) )
в. ( frac{mu_{0}}{4 pi} frac{2 I}{r}(pi-1) )
c. ( frac{mu_{0}}{4 pi} frac{2 I}{r}left(pi^{2}+1right) )
D. ( frac{mu_{0}}{4 pi} frac{2 pi I}{r} )
12
1025 Current ( i ) is flowing in a coil of area ( A & )
number of turns ( N, ) then magnetic
moment of the coil is ( M ) is equal to
A. ( N i A )
в. ( frac{N i}{A} )
c. ( frac{N i}{sqrt{A}} )
D. ( N^{2} A i )
12
1026 A conductor carries a constant current
along the closed path abcdefgha
nvolving 8 of the 12 edges each of
ength I.Find the magnetic dipole moment of the closed path. The answer
is ( M=x I l^{2} hat{j} ) then ( x ) is
12
1027 Two proton beams are moving in the
parallel direction. Which of the following
statements are correct.
This question has multiple correct options
A. Force between the proton beams will be attractive
B. Magnetic force between proton beams will be attractive
C. Repulsive force will be greater than attractive forces
D. Magnetic and electrostatic forces will cancel each other
12
1028 A circular coil of wire carries a current.
( P Q ) is a part of a very long wire carrying
a current and passing close to the circular coil. If the direction of currents
are those as shown in the Figure, what
is the direction of force acting on ( P Q ? )
A. Parallel to ( P Q ), towards ( P )
B. Parallel to ( P Q ), towards ( Q )
C. At right angles to ( P Q ), towards right
D. At right angles to ( P Q ), towards left
12
1029 A ( 2.00 m ) length of wire carrying ( 3.00 A ) of conventional current southward
through a ( 5.00 T ) magnetic field
directed straight up experience how much force due the field and in what
direction?
A. Amount of Force ( -7.5 N ), Direction of Force – west
B. Amount of Force ( -30.0 N ), Direction of Force – west
c. Amount of Force ( -7.5 N ), Direction of Force – east
D. Amount of Force ( -30.0 mathrm{N} ), Direction of Force – east
E. Amount of Force ( -3.33 mathrm{N} ), Direction of Force – north
12
1030 A long current carrying conductor of
length ( l ) is placed in a uniform magnetic
field strength ( B ). If current in conductor is ( i A, ) write down the formula of force
exerted on current carrying conductor.
What will be the maximum force? Write
its direction.
12
1031 An electric field ( boldsymbol{E} ) and a magnetic field
( B ) act over the same region in which an electron enters along the ( x ) -axis. The
combination of ( E ) and ( B ) which
permits the electron to go undeflected
is:
A. ( E ) along ( Y ) -axis and ( B ) along ( Y ) -axis
B. ( E ) along ( Y ) -axis and ( B ) along ( Z ) -axis
c. ( E ) along ( X ) -axis and ( B ) along ( Z ) -axis
D. ( E ) along ( Y ) -axis and ( B ) along ( X ) -axis
12
1032 Magnetic field is not associated with
A. a change in uniform motion
B. an accelerated charge.
c. a deaccelerated charge
D. a stationary charge.
12
1033 A light beam travelling in the ( x )
direction is described by the electric
field ( boldsymbol{E}_{boldsymbol{y}}=mathbf{3 0 0 v} / boldsymbol{m} sin left(boldsymbol{t}-frac{boldsymbol{x}}{c}right) cdot mathbf{A} mathbf{n} )
electron is constrained to move along
the y-direction with a speed of ( 2.0 times ) ( 10^{7} m / s . ) Find the maximum magnetic
force on the electron.
( mathbf{A} cdot 2 times 10^{-18} )
B . ( 2.5 times 10^{-18} )
C ( .3 times 10^{-18} )
D. ( 3.2 times 10^{-18} )
12
1034 The net magnetic flux through any closed surface, kept in a magnetic field is
A . zero
в. ( frac{mu_{0}}{4 pi} )
c. ( 4 pi mu_{0} )
D. ( frac{4 mu_{0}}{pi} )
12
1035 What kind of energy change takes place when a magnet is moved towards a coil having a galvanometer at its ends?
A. Mechanical energy changes to the magnetic energy.
B. Magnetic energy changes to the electrical energy
c. Mechanical energy changes to the electrical energy.
D. None of the above
12
1036 Two large parallel sheets having linear
current densities ( J ) and ( -J_{0} ) as shown
in figure, then magnetic field in region ( b ) is:-
( mathbf{b} )
begin{tabular}{|l|l|l|l|l|l|}
hline & ( mathrm{X} ) & ( mathrm{X} ) & ( mathrm{X} ) & ( mathrm{X} ) & ( mathrm{X} ) & ( -mathrm{J} ) \
hline
end{tabular}
A . zero
в. ( frac{mu_{0} J}{2} )
c. ( mu_{0} ).
D. None of these
12
1037 A long straight wire of radius R carries a
steady current ( I_{o}, ) uniformly distributed throughout the cross-section of the wire. The magnetic field at a radial distance r from the centre of the wire, in
the region ( r>R ), is?
A ( cdot frac{mu_{o} I_{o}}{2 pi r} )
В ( cdot frac{mu_{o} I_{o}}{2 pi R} )
( ^{mathbf{C}} cdot frac{mu_{o} I_{o} R^{2}}{2 pi r} )
D. ( frac{mu_{o} I_{o} r^{2}}{2 pi R} )
E ( cdot frac{mu_{o} I_{o} r^{2}}{2 pi R^{2}} )
12
1038 The number of turns per unit length of a
long solenoid is ( 10 . ) If its average radius is ( 5 mathrm{cm} ) and it carries a current of ( 10 mathrm{A} )
then the ratio of flux densities obtained
at the centre and at one endpoint will be
A .1: 2
B . 2: 1
c. 1: 1
D. 1: 4
12
1039 Two flat circular coils are made of two
identical wires each of length ( 20 mathrm{cm} ) one coil has 4 turns while the second
has ( 2 . ) If the same current flows through the two, then find ratio of the field at
their centre
12
1040 A loop carrying current ( I ) lies in the ( x )
( boldsymbol{y} ) plane as shown in figure. The unit
vector ( hat{k} ) is coming out of the plane of the paper. The magnetic moment of the
current loop is
( mathbf{A} cdot a^{2} I hat{k} )
B cdot ( left(frac{pi}{2}+1right) a^{2} I hat{k} )
c. ( -left(frac{pi}{2}+1right) a^{2} I hat{k} )
D. ( (2 pi+1) a^{2} I hat{k} )
12
1041 Find the magnetic moment of the spiral
with a given current.
A ( cdot p=25 m A cdot m^{2} )
B . ( p=15 mathrm{mA} cdot mathrm{m}^{2} )
C ( cdot p=30 mathrm{mA} cdot mathrm{m}^{2} )
D. ( p=50 mathrm{mA} cdot mathrm{m}^{2} )
12
1042 The radius of the curved part of the wire
is ( R=100 m m, ) the linear parts of the
wire are very long. Find the magnetic induction at the point ( O ) if the wire
carrying a current ( I=8.0 A ) has the
shape shown in the figure.
в. ( 0.60 mu T )
( c .0 mu T )
D. ( 0.70 mu T )
12
1043 An ( alpha ) particle and a proton travel with same velocity in a magnetic field perpendicular to the direction of their
velocities. Find the ratio of the radii of
their circular paths.
A .4:
B. 1:
c. 2:
D. 1:
12
1044 If a charged particle projected in a gravity-free room deflects This question has multiple correct options
A. there must be an electric field
B. there must be a magnetic field
c. both fields cannot be zero
D. both fields can be non-zero
12
1045 Two thin long wires carry currents ( boldsymbol{I}_{mathbf{1}} )
and ( I_{2} ) along ( x ) -and ( y ) -axes respectively
as shown in figure. Consider the points
only in ( x ) -y plane.
This question has multiple correct options
A. Magnetic field is zero at least at one point in each quadrant
B. Magnetic field can be zero somewhere in the first quadrant
c. Magnetic field can be zero somewhere in the second quadrant
D. Magnetic field is non-zero in second quadrant
12
1046 A very long straight conducting wire, lying along the z-axis, carries a current of ( 2 A . ) The integral ( oint vec{B} . d vec{l} ) is computed along the straight line ( P Q ), where ( P ) has
the coordinates ( (2 c m, 0,0) ) and ( Q ) has
the coordintes ( (2 c m, 2 c m, 0) . ) The integral has the magnitude (in Sl units)
( ^{A} cdot frac{pi}{2} times 10^{-7} )
В . ( 8 pi times 10^{-7} )
D. ( pi times 10^{-7} )
12
1047 A circular coil carrying a current I has
radius R and number of turns N. If all
the three, i.e., the current I, radius R and number of turns ( mathrm{N} ) are doubled, then
magnetic field at its centre becomes.
A. Double
B. Half
c. Four times
D. One fourth
12
1048 A solenoid with a soft iron core is called
( mathbf{a} )
A. Electromagnet
B. Magnettet
c. conducts
D. Insulator
12
1049 Assertion
An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube
Reason
Electric field requires low voltage.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
1050 The speed at any point is
A ( cdot sqrt{frac{3 q E y}{m}} )
B. ( sqrt{frac{q E y}{m}} )
c. ( sqrt{frac{q E y}{2 m}} )
D. ( sqrt{frac{2 q E y}{m}} )
12
1051 Assertion
Cyclotron is a device which is used to
accelerate the positive ions.
Reason
Cyclotron frequency depends upon the velocity
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
1052 State biot-savart law in vector from
along with expression.
12
1053 A long straight conductor, carrying a
current ( i, ) is bent to form an almost
complete circular loop of radius ( r ) as
shown. The magnetic field at the centre
of the loop:
A ( cdot ) has magnitude ( frac{mu_{0} i}{r}left(1-frac{1}{pi}right) )
B. has magnitude ( frac{mu_{0} i}{r}left(1+frac{1}{pi}right) )
c. has magnitude ( frac{mu_{0} i}{2 r}left(1-frac{1}{pi}right) )
D. has magnitude ( frac{mu_{0} i}{2 r}left(1+frac{1}{pi}right) )
12
1054 When the free ends of a tester are
dipped into a solution, the magnetic needle shows deflection.
A. True
B. False
c. Ambiguous
D. Data insufficient
12
1055 In the adjoining diagram, a currentcarrying loop pqrs placed with its sides parallel to a long current-carrying wire.
The currents ( i_{1} ) and ( i_{2} ) in the wire and
loop are ( 20 mathrm{A} ) and 16 A respectively. If ( a= ) ( 15 mathrm{cm}, mathrm{b}=6 mathrm{cm}, ) and ( mathrm{d}=4 mathrm{cm}, ) what will
be the force on current ( i_{2} ) in the loop is
clockwise instead of anticlockwise?
12
1056 Two identical galvanometers are joined by connecting wires. One of them is placed on the table and the other is held in the hand. One in the hand is shaken
violently so that it shows a deflection of 10 division. The reading in the other
galvanometer (on the table) is
A . zero
B. 10 division
c. 5 division
D. insufficient data to reply
12
1057 Which one of the following is NOT
correct?
A. Dimensional formula of thermal conductivity (K) is ( M^{1} L^{1} T^{-3} K^{-1} )
B. Dimensional formula of potential (V) is ( M^{1} L^{2} T^{-3} A^{-1} )
C. Dimensional formula of permeability of free space ( left(mu_{0}right) ) is ( M^{1} L^{1} T^{-2} A^{-2} )
D. Dimensional formula of RC is ( M^{0} L^{0} T^{-1} )
12
1058 A mono energetic electron beam with the speed of ( 5.2 times 10^{6} m s^{-1} ) enters into
the magnetic field of induction ( 3 x )
( 10^{-4} T, ) directed normal to the
beam. Then the radius of the circle
traced by the beam:
( left(operatorname{given} e / m=1.76 times 10^{11} C K g^{-1}right) )
B. ( 0.98 m )
( c .0 .089 m )
D. ( 9.8 m )
12
1059 A coil of area ( A ), turns ( N ) and carrying current ( i ) is placed with its face parallel to the lines of magnetic induction ( B )
The work done in rotating the coil
through an angle of ( 180^{0} ) is
( mathbf{A} cdot i N A B )
в. 2 iNA ( B )
c. ( frac{i N A B}{2} )
D. Zero
12
1060 Magnetic field in a region is given by ( vec{B}=B_{o} x hat{k} . ) Two loops each of side a is
placed in this magnetic region in the ( x ) y plane with one of its sides on x-axis. If
( F_{1} ) is the force on loop 1 and ( F_{2} ) be the
force on loop 2 then:
A ( . F_{1}=F_{2}=0 )
B. ( F_{1}>left{F_{3},{2} $ $right. )
( mathbf{c} cdot F_{2}>F_{1} )
D. ( F_{1}=F_{2} neq 0 )
12
1061 A steady current ( I ) flows along an infinitely long hollow cylindrical conductor of radius ( mathbf{R} . ) This cylinder is placed coaxially inside an infinite solenoid of radius ( 2 mathrm{R} ). The solenoid has
n turns per unit length and carries a
steady current ( I . ) Consider a point ( mathbf{P} ) at a
distance r from the common axis. The
correct statement ( (s) ) is (are):
This question has multiple correct options
A. in the region ( 0<mathrm{r}<mathrm{R} ), the magnetic field is non-zero
B. in the region ( R<r<2 R ), the magnetic field is along the common axis
c. in the region ( mathrm{R}<mathrm{r}2 R ), the magnetic field is non-zero
12
1062 Find Ampere force acting on the frame.
A. ( F=4.0 mu N )
в. ( F=0.80 mu N )
c. ( F=0.40 mu N )
D. ( F=8.0 mu N )
12
1063 An electron is moving vertically downwards at any place. The direction of magnetic force acting on it due to horizontal component of earth’s magnetic field will be
A. towards east
B. towards west
c. towards north
D. towards south
12
1064 If the orientation of the current loop in a magnetic field is changed then potential energy of loop is also changed.Enter 1 if True and 0 if False. 12
1065 The parts of two concentric circular arcs joined by two radial lines and carries current ( i . ) The arcs subtend an
angle ( theta ) at the center of the circle. The magnetic field at the centre 0 , is
A ( cdot frac{mu_{0} i(b-a) theta}{4 pi a b} )
В. ( frac{mu_{0} i(b-a)}{pi-theta} )
c. ( frac{mu_{0} i(b-a) theta}{pi a b} )
D. ( frac{mu_{0} i(a-b)}{2 pi a b} )
12
1066 Deduce the relation for the magnetic induction at a point along the axis of a
circular coil carrying current.
12
1067 By which factor the magnetic field produced by a wire at distance ( 2 mathrm{cm} ) from the wire than at ( 4 mathrm{cm} ) from the wire
is stronger if wire length is ( 2 mathrm{m} ) and carries a 10 -amp current :
A .2
B. ( 2 sqrt{2} )
( c cdot 4 )
D. ( 4 sqrt{2} )
( E )
12
1068 An infintely long straight wire carrying current of ( 10 mathrm{A} ) is passing through the centre of the above circuit vertically with the direction of the current being into the plane of the circuit.What is the
force acting on the wire at the centre due to the current in the circuit?What is
the force acting on the arc ( A C ) and the straight segment CD due to the current at the centre?
12
1069 In a moving cell galvanometer, we use a radial magnetic field so that the galvanometer scale is
A. logarithmic
B. exponential
c. linear
D. none of the above
12
1070 Three moving coil galvanometer ( boldsymbol{A}, boldsymbol{B} ) and ( C ) are made of coils of three
different material having torsional constant ( 1.8 times 10^{-8}, 2.8 times 10^{-8} ) and
( 3.8 times 10^{-8} ) respectively. If the three
galvanometers are identical in all other respect, then in which of the above cases, current sensitivity is maximum?
A. ( A )
в. ( C )
( c . B )
D. same in each case
12
1071 Non-relativistic protons move
reactilinearly in the region of space where there are uniform mutually perpendicular electric and magnetic fields with E and B. The trajectory of the
protons lie in the plane ( X ) -Y as shown in
fig. and forms an angle ( phi phi ) with ( X ) -axis. If the pitch of the helical trajectory
along which the protons will move after
the electric field is switched off is
Pitch ( =frac{boldsymbol{x} boldsymbol{pi} boldsymbol{m} boldsymbol{E}}{boldsymbol{q} boldsymbol{B}^{2}} boldsymbol{t a n} boldsymbol{phi} ). Find ( boldsymbol{x} )
12
1072 Two long, thin, parallel conductors separated by a distance carry currents
( i_{1} ) and ( i_{2} . ) The force per unit length on one of them is F. Then
This question has multiple correct options
( mathbf{A} cdot F proptoleft(i_{1} i_{2}right) )
B . ( F proptoleft(i_{1} i_{2}right)^{2} )
( mathbf{c} cdot F propto frac{1}{d^{2}} )
( D cdot F propto frac{1}{d} )
12
1073 A current carrying ring is placed in a magnetic field. The direction of the field
is perpendicular to the plane of the ring. Which of the following correct for this? This question has multiple correct options
A. There is no net force on the ring
B. The ring will tend to expand
c. The ring will tend to contract
(b) or
D. Either
(c) depending on the directions of the current in the ring and the magnetic field
12
1074 ( boldsymbol{x}=mathbf{0}, boldsymbol{y}=mathbf{0}, boldsymbol{z}=+mathbf{0 . 5 0 0 m} ) 12
1075 The relation between magnetic field and current is given by Biot-Savart
law. Illustrate Biot-Savart law with
necessary figure.
12
1076 How does doubling number of turns in a
toroidal coil affect the value of
magnetic flux density?
A. Four times
B. Eight times
c. Half
D. Double
12
1077 Two long thin conductors ( 10 mathrm{cm} ) apart
carry currents in the ratio 1: 2 in the
same direction. The magnetic field
midway between them is ( 2 times 10^{-3} )
Tesla. The force on 1 metre length of any conductor will be :
( mathbf{A} cdot 2 pi times 10^{-3} ) Newton
B. ( 2 times 10^{-3} ) Newton
c. ( pi ) Newton
D. 1 Newton
12
1078 If the galvanometer shows no deflection
then the value of ( mathrm{R} ) for the circuit shown
in the figure is ( length ( A B=100 mathrm{cm} ) )
A. 30 ohms
B. 60 ohms
( c .10 ) ohms
D. 120 ohms
12
1079 Assertion
The magnetic field produced by a
current carrying solenoid Is
independent of its length and cross-
sectional area.
Reason
The magnetic field inside the solenoid
is uniform.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
1080 Assertion
When current is represented by a straight line, the magnetic field will be circular.
Reason
According to Fleming’s left hand rule, direction of force is parallel to the magnetic field
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
1081 A wire bent as shown in Fig is oriented
along yz plane. Find the magnetic field
at ( P ) and ( P_{1} )
A ( cdot frac{mu_{0} I}{4 a}, frac{mu_{0} I}{2 pi x_{x}} )
B. ( frac{mu I}{4 a}, frac{mu I}{2 pileft(x^{2}+a^{2}right)} )
C. ( frac{mu_{0} I}{4 a}, frac{mu_{0} I}{2 pi aleft(x^{2}+a^{2}right)} )
D. none of thes
12
1082 If a positively charged particle is
moving as shown in the figure, then it
will get deflected due to magnetic field towards:
A . ( +x ) direction
B. +y direction
c. – x direction
D. tz direction
12
1083 Fleming’s left hand rule tells us about
direction of magnetic force due to
current in magnetic field, but what is its magnitude?
12
1084 The nature of the magnetic field in a moving coil galvanometer is Radial magnetic field. State True or False. 12
1085 A toroid with mean radius ( r_{0} ) and
diameter ( 2 a ) has ( N ) turns carrying current I. What is the magnetic field B inside the toroid?
A ( cdot frac{mu_{0} N I}{2 pi r_{0}} )
В. ( frac{mu_{0} N I}{2 pileft(r_{0}+aright)} )
c. ( frac{mu_{0} N I}{pileft(r_{0}+aright)} )
D. zero
12
1086 Two parallel wires each of length ( 5 m ) are
placed at a distance of ( 10 mathrm{cm} ) apart in
air. They carry equal currents along the same direction and experience a mutually attractive force of ( 3.6 times )
( 10^{-4} N . ) Find the current through the
conductors.
12
1087 The galvanometer deflection, when key
( K_{1} ) is closed but ( K_{2} ) is open, equals ( theta_{0} )
(see figure). On closing ( K_{2} ) also and
adjusting ( R_{2} ) to5 ( Omega, ) the deflection in
galvanometer becomes ( frac{theta_{0}}{5} ). The
resistance of the galvanometer is, then, given by [Neglect the internal resistance of battery ( ] )
A . ( 12 Omega )
B . ( 25 Omega )
( c .5 Omega )
D. ( 22 Omega )
12
1088 Derive an expression for the force per unit length acting on the two straight parallel current carrying conductors. In which condition will this force be
attractive and repulsive? Define the
standard unit of current
12
1089 A closely wound, circular coil with
radius ( 2.40 mathrm{cm} ) has 800 turns. The
distance ( x ) from the centre of the coil,
along the axis, at which the magnetic field is half of its value at the centre, is
( 184 times 10^{-x} m . ) Find the value of ( x )
12
1090 The strength of an electromagnet can be increased by.
A. increasing the current in the coil
B. decreasing the current in the coil
c. decreasing the number of turns in the coil
D. increasing the length of air gap between its poles
12
1091 An elastic circular wire of length ( ell )
carries a current ( I_{0} . ) It is placed in a
uniform magnetic field ( vec{B} ) (out of paper)
such that its plane is perpendicular to the direction of ( vec{B} ). The wire will
experience:
A. No force
B. A stretching force
c. A compressive force
D. A touque
12
1092 Assertion
No net force acts on a rectangular coil
carrying a steady current when
suspended freely in a uniform magnetic
field.
Reason
Force on coil in magnetic field is always
non-zero.
A. If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B. If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
C. If Assertion is correct but Reason is incorrect.
D. If Assertion is incorrect but Reason is correct.
12
1093 ( underbrace{ } ) 12
1094 A rectangular loop carrying a current is situated near a long straight wire such that the wire is parallel to the one
of the sides of the loop and is in the
plane of the loop. If a steady current lis established in wire as shown in figure,
the loop will:
A. rotate about an axis parallel to the wire
B. move away from the wire or towards right
c. move towards the wire
D. remain stationary
12
1095 Two identical circular loops PP. 12
1096 ( A 25 mathrm{cm} ) long solenoid has radius ( 2 mathrm{cm} ) and 500 total number of turns. It carries
a current of 15 A. If it is equivalent to magnet of the same size and magnetization ( vec{M} ) Magnetic moment vloume), then ( overrightarrow{|M|} ) is.
B. 30000Am”
c. ( 30000 pi A m^{-1} )
D. ( 3 pi A m^{-1} )
12
1097 If the force per unit length on wire ( boldsymbol{B} ) is
given by ( 2.88 times 10^{-x} N m^{-1} . ) Find ( x )
12
1098 The self-inductance of an air core
solenoid of 100 turns is 1 m ( H ). The self-
inductance of another Solenoid of 50
turns (with the same length and crosssectional area) with a core having relative permeability 500 is
A . ( 125 mathrm{mH} )
B. 24 mH
c. ( 60 mathrm{mH} )
D. 30 mH
E. ( 45 mathrm{mH} )
12
1099 The electric current in a circular coil of
two turns produced a magnetic induction of ( 0.2 T ) at its centre. The coil
is unwound and is rewound into a
circular coil of four turns. The magnetic induction at the centre of the coil now
is, in ( T: )
(if same current flows in the coil)
A . 0.2
B. 0.4
( c .0 .6 )
D. 0.8
12
1100 A positively charged disk is rotated clockwise as shown in the figure. The
direction of the magnetic field at point
( A ) in the plane of the disk is
( A cdot otimes ) into the page
B. ( rightarrow ) towards right
( mathbf{c} . leftarrow ) towards left
D. odot out of the page
12
1101 If ( 6 mathrm{mm} ) is the distance moved by the
thimble on the main scale for 6
rotations then pitch of the screw is :
( mathbf{A} cdot 1 mathrm{mm} )
B. ( 1 mathrm{cm} )
( c .0 .1 mathrm{mm} )
D. 0.01 cm
12
1102 The magnetic lines of force inside a current carrying solenoid are:
A. along the axis and parallel to each other
B. perpendicular to the axis and parallel to each other
c. circular and do not intersect each other
D. circular and intersect each other
12
1103 A beam of cathode rays moves from left
to right in a plane of the paper and it enters into a uniform magnetic field acting perpendicular to the plane of the paper and inwards. Now, the cathode rays are deflected:
A. Downwards
B. Upwards
c. In a direction perpendicular to the plane of the paper and inwards
D. In a direction perpendicular to the plane of the paper and outwards
12
1104 The coil of the moving coil galvanometer is wound over an aluminium frame
A. because aluminium is a good conductor
B. because aluminium is very light.
c. because aluminium is comparatively cheaper
D. to provide electro-magnetic damping.
12
1105 A wire carrying a current of ( 5 A ) is placed perpendicular to a magnetic induction of ( 2 T . ) The force on each centimeter of
the wire is
A. ( 0.1 N )
в. ( 10 N )
c. ( 100 N )
D. ( 1 N )
12
1106 How will crowding the wires of a solenoid, more closely together, will
affect the strength of the field inside it?
A. Field strength increases
B. Field strength decreases
c. Can’t be said
D. Field strength will remain unchanged
12
1107 A solenoid of length ( 1.0 m, ) radius ( 1 mathrm{cm} )
and total turns 1000 wound on it,
carries a current of 5 A. Calculate the
magnitude of the axial magnetic field inside the solenoid. If an element was to
move with a speed of ( 104 m / s ) along the
axis of this current carrying solenoid, what would be the force experienced by this electron?
12
1108 Obtain an expression for the self-
inductance of a long solenoid.
12
1109 Electrons at rest are accelerated by a
potential of ( boldsymbol{V} ) volt. These electrons enter the region of space having a uniform, perpendicular magnetic induction field ( B ). The radius of the path
of the electrons inside the magnetic field is:
A ( .1 / B sqrt{m V / e} )
B. ( frac{sqrt{2 m V / e}}{B} )
c. ( m V / q B )
D. ( 1 / B sqrt{V / e} )
12
1110 A uniform electric field and a uniform
magnetic field acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity, then
A. It will turn towards left of direction of motion
B. It will turn towards right to direction of motion
c. Its velocity will increase
D. Its velocity will decrease
12
1111 Draw a labelled diagram showing the magnetic field lines of a loop carrying current. Mark the direction of current
and the direction of
magnetic field by arrows in your diagram.
12
1112 Two particles ( X ) and ( Y ) having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field
and describe circular paths of radii ( boldsymbol{R}_{1} )
and ( R_{2}, ) respectively. The ratio of
masses of ( X ) and ( Y ) is
( ^{mathbf{A}} cdotleft(frac{R_{1}}{R_{2}}right)^{1 / 2} )
B. ( left(frac{R_{2}}{R_{1}}right) )
( ^{mathbf{c}} cdotleft(frac{R_{1}}{R_{2}}right)^{2} )
D. ( left(frac{R_{1}}{R_{2}}right) )
12
1113 toppr LOGIN JolN Now
Q Type your question
Which table gives the correct directions
for the magnetic field at the two
positions around the wire?
wire field on right side of
(6)
wire head on with conventional
current flow out of page
( A )
begin{tabular}{|l|l|}
hline & Direction of Field \
hline Right of the Wire & toward right side of page \
Below the Wire & toward bottom of page \
hline
end{tabular}
B. begin{tabular}{|l|c|}
hline & Direction of Field \
hline Right of the Wire & toward left of page \
Below the Wire & toward top of page \
hline
end{tabular}
( mathbf{c} )
begin{tabular}{|l|l|}
hline & Direction of Field \
hline Right of the Wire & toward top of page \
Below the Wire & toward right side of page \
hline
end{tabular}
D.
begin{tabular}{|l|l|}
hline & Direction of Field \
hline Right of the Wire & toward bottom of page \
Below the Wire & toward left side of page \
hline
end{tabular}
( E )
begin{tabular}{|l|l|}
hline & Direction of Field \
hline Right of the Wire & toward lower left portion of page \
Below the Wire & toward upper right portion of page \
hline
end{tabular}
12
1114 Draw the magnetic field lines of the field produced by a current carrying circular loop. Explain with reason whether the field will be stronger at a
point at the center of loop or near the circumference of loop.
12
1115 A long horizontal rigidly supported wire
carries a current ( i_{a}=96 A . ) Directly
above it and parallel to it at a distance,
another wire of ( 0.144 N ) weight per
metre is carrying a current ( i_{b}=24 A, ) in
a direction same as the lower wire. If the
weight of the second wire is balanced
by the force due to magnetic repulsion, then its distance (in mm) from the
lower wire is:
A . 9.6
B. 4.8
c. 3.2
D. 1.6
12
1116 In which case would the particle move in a straight line along the negative direction of y-axis (i.e., move along – ( hat{y} ) )?
A. ( (I I I)(i i)(P) )
B . ( (I I)(i i i)(Q) )
c. ( (I V)(i i)(S) )
D. ( (I I I)(i i)(R) )
12
1117 ( A, B ) and ( C ) are parallel conductors of
equal lengths carrying currents ( boldsymbol{I}, boldsymbol{I} ) and
( 2 I ) respectively. Distance between ( A )
and ( B ) is ( x . ) Distance between ( B ) and ( C )
is also ( x . F_{1} ) is the force exerted by ( B ) on
( A . F_{2} ) is the force exerted by ( C ) on ( A )
Choose the correct answer.
( mathbf{A} cdot F_{1}=2 F_{2} )
B . ( F_{2}=2 F_{1} )
( mathbf{c} cdot F_{1}=F_{2} )
D. ( F_{1}=-F_{2} )
12
1118 toppr
Q Type your question_
constant speed. The field deflects the
particle, a distance h above the original
line of flight as shown in the Figure. The
particle leaves the field region with
momentum, if ( h<<d, ) of about :
( frac{q B d^{2}}{2 h}, ) making an angle ( frac{2 h}{d} ) with initial direction
B. ( frac{q B h^{2}}{2 d}, ) making an angle ( frac{2 h}{d} ) with initial direction
( frac{q B d}{2}, ) making an angle ( frac{2 d}{h} ) with initial direction
( frac{q B h}{2}, ) making an angle ( frac{2 d}{h} ) with initial direction
12
1119 An electron passes undeflected
through perpendicular electric and magnetic fields of intensity ( 3.4 times )
( mathbf{1 0}^{mathbf{3}} boldsymbol{V} / boldsymbol{m} ) and ( mathbf{2} times mathbf{1 0}^{-mathbf{3}} boldsymbol{W} boldsymbol{b} / boldsymbol{m}^{mathbf{2}} )
respectively. Then its velocity is:
A ( .1 .7 times 10^{6} mathrm{m} / mathrm{s} )
B . ( 6.8 times 10^{6} mathrm{m} / mathrm{s} )
( c cdot 6.8 m / s )
D. ( 1.7 times 10^{8} mathrm{m} / mathrm{s} )
12
1120 A rectangular loop, carrying current ( i, ) is
lying near a long straight conductor PQ as shown in the figure in such way that
the wire is parallel to one of the sides of the loop and is in the plane of the loop. If
constant current ( I ) is passed in the wire
then the loop will
A. move towards the wire
B. move away from the wire
c. remain stationary
D. rotate about an axis parallel to the wircre
12
1121 In cyclotron, for a given magnet, radius of the semicircle traced by positive ion is directly proportional
to (v=velocity of positron ion)
A ( cdot v^{-2} )
B . ( v^{-1} )
( c )
( D cdot v^{2} )
12
1122 A planar coil of area ( 7 mathrm{m}^{2} ) carrying an anti-clockwise current 2 A is placed in an extemal magnetic field ( vec{B}=(0.2 hat{i}+ ) ( 0.2 hat{j}-0.3 hat{k}), ) such that the normal to the plane is along the ( operatorname{line}(3 hat{i}-5 hat{j}+ )
4 ( hat{k} ) ). Select correct statements from the
following. ( Consider Normal of the coil and Magnetic moment vectors to be in the same direction
This question has multiple correct options
A. The potential energy of the coil in the given orientation is 6.4
B. The angle between the normal (positive) to the coil and the external magnetic field is ( cos ^{-1}(0.57) )
c. The potential energy of the coil in the given orientation is 3.2
D. The magnitude of magnetic moment of the coil is about ( 14 A m^{2} )
12
1123 Derive expression for the self
inductance of a solenoid. What factors
affect it?
12
1124 A long straight wire is carrying current
( boldsymbol{I}_{1}=mathbf{2} / mathbf{5} boldsymbol{A} ) in ( +mathbf{z} ) direction.The ( mathbf{x}-mathbf{y} ) plane
contains a closed circular loop carrying
current ( boldsymbol{I}_{2}=mathbf{5} / mathbf{2} boldsymbol{A} ) and not encircling
the straight wire, then the force (in newton) on the loop will be ? (Radius of
the circular loop ( boldsymbol{R}=mathbf{3} / mathbf{4 m} ) ).
12
1125 A small magnet is placed perpendicular to a uniform magnet field. The forces acting on the magnet will result in :
A. Rotational motion
B. Translatory motion
c. No motion at al
D. Translational and rotational motion both
12
1126 I wo very long stralght parallel wires
having current ( I ) and ( 2 I ) as shown in the
figure. A point charge ( q ) is at a point
equidistant from the two wires in the plane of the wires. Its instantaneous
velocity ( bar{v} ) is parallel to currents in the plane. The magnitude of force due to the magnetic field acting on the charge at
this instant is:
A ( cdot frac{q v mu_{0} l}{2 pi d} )
B. ( frac{2 q v mu_{0} l}{3 pi d} )
C. ( frac{6 q v mu_{0} l}{2 pi d} )
D. ( frac{q v mu_{0} l}{pi d} )
12
1127 A current-carrying circular coil of magnetic moment ( M ) is situated in a
magnetic field ( B ). The work done in
deflecting it from an angle ( 0^{circ} ) to ( theta^{circ} ) will
be :
( A . M B )
В. ( M B(1-cos theta) )
( mathrm{c} cdot-M B )
D. ( M B(1-sin theta) )
12
1128 Draw a neat and labelled diagram of
suspended coil type moving coil galvanometer.
12
1129 If only ( 2 % ) of the main current is to be
passed through a Galvanometer of resistance ( G, ) the resistance of shunt
should be :
A. ( G / 50 )
в. ( G / 49 )
c. ( 50 / G )
D. ( 49 G )
12
1130 Two thin long parallel wires separated by a distance ( b ) are carrying a current ( I ) ampere each. The magnitude of the force per unit length exerted by one wire on the other is
A ( frac{mu_{0} I^{2}}{b^{2}} )
в. ( frac{mu_{0} I^{2}}{2 pi b} )
c. ( frac{mu_{0} I}{2 pi b} )
D. ( frac{mu_{0} I}{2 pi b^{2}} )
12
1131 The ratio of the magnetic field at the centre of a current carrying circular wire and the magnetic field at the centre of a square coil made from the same length of wire is
A ( cdot frac{pi}{2 sqrt{2}} )
в. ( frac{pi}{4 sqrt{2}} )
c. ( frac{pi^{2}}{4 sqrt{2}} )
D. ( frac{pi^{2}}{8 sqrt{2}} )
12
1132 When a galvanometer is shunted with a
( 4 Omega ) resistance, the deflection is reduced
to one – fifth. If the galvanometer is
further shunted with a ( 2 Omega ) wire,
determine current in galvanometer now
if initially current in galvanometer is ( I_{0} ) (given main current remain same).
A ( cdot I_{0} / 13 )
the
в. ( I_{0} / 5 )
c. ( I_{0} / 8 )
D. ( 5 I_{0} / 13 )
12
1133 A wire of length ( l ) carries a current ( i ) along the ( x ) -axis.A magnetic field ( vec{B}= ) ( B_{o}(hat{j}+hat{k}) ) exists in the space.Find the
magnitude of the magnetic force acting on the wire.
12
1134 A proton enters a magnetic field of flux density ( 1.5 W b / m^{2} ) with a speed of ( 2 times )
( 10^{7} mathrm{m} / mathrm{s} ) at angle of ( 30^{circ} ) with the field.
The force on a proton will be
A. ( 0.44 times 10^{-12} N )
B . ( 2.4 times 10^{-12} N )
c. ( 24 times 10^{-12} N )
D. ( 0.024 times 10^{-12} N )
12
1135 Can cyclotron accelerate uncharged
particles?Why?
12
1136 The strength of magnetic field inside a long current carrying straight solenoid is:
A. more at the ends than at the centre
B. minimum in the middle
c. same at all points
D. found to increase from one end to the other
12
1137 A wire carrying current of ( 10 A ) supports
a wire of ( 10 mathrm{cm} ) long and weighing ( 1 mathrm{g} )
vertically above it at a distance of ( 1 mathrm{cm} )
The current that is passing through the wire is :
( mathbf{A} cdot 490 A )
B . ( 205 A )
( c cdot 408 A )
D. ( 316 A )
12
1138 In an hydrogen atom, the electron is making ( 6.6 times 10^{15} )rps. If the radius of
the orbit is ( 0.53 times 10^{-10} m, ) then the
equivalent magnetic dipole moment is approximately
( mathbf{A} cdot 10^{-29} A m^{2} )
B . ( 10^{-27} mathrm{Am}^{2} )
c. ( 10^{-23} A m^{2} )
D. ( 10^{-19} mathrm{Am}^{2} )
12
1139 A solenoid has a core of a material with
relative permeability of 500. The windings of the solenoid are insulated
from the core and carry a current of ( 2 mathrm{A} ) If the number of turns is 1000 per
meter, then magnetisation will be then
A . ( 7.78 times 10^{5} mathrm{Am}^{-1} )
В. ( 8.88 times 10^{5} mathrm{Am}^{-1} )
c. ( 9.98 times 10^{5} mathrm{Am}^{-} )
D. ( 10.2 times 10^{5} mathrm{Am}^{-1} )
12
1140 A free charged particle moves through a magnetic field. The particle may undergo a change in
A. Speed
B. Energy
c. Direction of motion
D. None of these
12
1141 A uniformly charged ring of radius ( R ) is
rotated about its axis with constant
linear speed ( v ) of each of it’s particles.
The ratio of electric field to magnetic
field at a point ( boldsymbol{P} ) on the axis of the ring
at a distant ( x=R ) from the centre of
the ring is :
( (c text { is speed of light }) )
A ( frac{c^{2}}{v} )
в. ( frac{v^{2}}{c} )
c. ( frac{c}{v} )
( D cdot underline{v} )
12
1142 A solenoid of length ( 50 mathrm{cm}, ) having 100 turns carries a current of 2.5 A. The
magnetic field at one end of the solenoid is:
A. 3.14 ( times 10^{4} ) न
B. 6.28 ( times 10^{4} ) Т
c. ( 1.57 times 10^{4} ) न
D. 9.42 ( times 10^{4} ) न
12
1143 Shunt wire should be
( A ). Thick and long
B. Thick and short
c. Thin and long
D. Thin and short
12
1144 The magnetic field of a solenoid carrying a current is similar to that of a
B. bar magnet
c. toroid
D. none
12
1145 toppr
Q Type your question
from point ( P ) to ( Q ) as shown in figure. The velocities at ( P ) and ( Q ) are respectively, ( boldsymbol{v} overrightarrow{boldsymbol{i}} ) and ( -2 v vec{j} . ) Then which of the following
statements ( (A, B, C, D) ) are the correct?
(Trajectory shown in schematic and not
to scale)
( (mathbf{A}) boldsymbol{E}=frac{mathbf{3}}{mathbf{4}}left(frac{boldsymbol{m} boldsymbol{v}^{2}}{boldsymbol{q} boldsymbol{a}}right) )
(B) Rate of work done by the electric field at ( P ) is ( frac{3}{4}left(frac{m v^{3}}{a}right) )
(C) Rate of work done by both the fields
at Qis zero
(D) The difference between the
magnitude of angular momentum of
the particle at ( P ) and ( Q ) is 2 mav.
( A cdot(A),(B),(C),(D) )
B. ( (A),(C),(D) )
( c cdot(B),(C),(D) )
D. ( (A),(B),(C) )
12
1146 Two parallel wires ( 1 m ) apart carry
currents of ( 1 A ) and ( 3 A ) respectively in
opposite directions. The force per unit length acting between these two wires is
A ( .6 times 10^{-7} mathrm{Nm}^{-1} ) repulsive
B. ( 6 times 10^{-7} mathrm{Nm}^{-1} ) attractive
c. ( 6 times 10^{-5} mathrm{Nm}^{-1} )repulsive
D. ( 6 times 10^{-5} mathrm{Nm}^{-1} ) attractive
12
1147 Why does a current carrying freely suspended solenoid rest along a
particular direction?
A. It points towards the geometric poles of the earth
B. A current carrying solenoid behaves like a bar magnet
C. It points in the direction of the flow of current
D. None of the above
12
1148 The work done in turning a magnet of magnetic moment ( M ) by an angle of ( 90^{circ} )
from the meridian is ( n ) times the
corresponding work done to turn it through an angle of ( 60^{circ} ) from the
meridian, where ( n ) is given by :
A ( cdot frac{1}{2} )
B. 2
( c cdot frac{1}{4} )
D.
12
1149 A long straight wire along the z-axis carries a current lin the negative z direction. The magnetic vector field ( bar{B} ) at a point having coordinates ( (x, y) ) in the z=0 plane is:
A ( cdot frac{mu_{0} I(y hat{i}-x hat{j})}{2 pileft(x^{2}+y^{2}right)} )
B. ( frac{mu_{0} I(x hat{i}-y hat{j})}{2 pileft(x^{2}+y^{2}right)} )
c. ( frac{mu_{0} I(x hat{j}-y hat{i})}{4 pileft(x^{2}+y^{2}right)} )
D. ( frac{mu_{0} I(x hat{i}-y hat{j})}{4 pileft(x^{2}+y^{2}right)} )
12
1150 An ( alpha ) – particle moves from ( mathrm{E} ) to ( mathrm{W} ) in a magnetic field perpendicular to the plane of the paper and into the paper. The particle is deflected towards:
A. East
B. west
c. south
D. North
12
1151 The force that a magnetic field exerts on a current is always perpendicular to
A. Field
B. Velocity
c. current
D. All of the above
12
1152 mounted on one end of a balance beam
and introduced between the poles of an
electromagnet as shown in fig. The area
of the coil is ( S=1 c m^{2}, ) the length of the
right arm of the balance beam is ( l= )
( 30 mathrm{cm} . ) When there is no current in the
coil the balance is in equilibrium. On
passing a current ( I=22 m A ) through
the coil, equilibrium is restored by
putting an additional weight of mass
( boldsymbol{m}=mathbf{6 0} mathrm{mg} ) on the balance pan. Find the
magnetic induction field (in terms of
( left.times 10^{-1} Tright) ) between the poles of the electromagnet, assuming it to be uniform:
12
1153 Identify the odd one out:
Magnet, Solenoid, Compass needle, Oven.
12
1154 State Ampere’s circuital law and arrive
at the expression for the magnetic field
near a straight infinite current carrying wire.
12
1155 A magnetic field due to a long straight wire carrying a current I is proportional
to
( A )
B . ( I^{2} )
c. ( I^{3} )
D. ( sqrt{I} )
12
1156 Assertion
no electric current will be present
within a region having uniform and
constant magnetic field.
Reason
Within a region of uniform and constant magnetic field ( vec{B} ), the path integral of magnetic field ( oint vec{B} cdot overrightarrow{d l} ) along any closed path is zero. Hence, from Ampere circuital law ( oint vec{B} cdot overrightarrow{d l}=mu_{0} I ) (where the
given terms have usual meaning), no
current can be present within a region having a uniform and constant magnetic field
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
1157 A current carrying small loop of one turn behaves like a small magnet. If ( A ) be its
area, ( M ) its magnetic moment, the current in the loop will be
A ( cdot frac{M}{A} )
в. ( frac{A}{M} )
c. ( M A )
D. ( A^{2} M )
12
1158 Two protons move parallel to each other,
keeping distance r between them, both moving with same velocity ( overrightarrow{mathrm{v}} ). Then the ratio of the electric and magnetic force of interaction between them is:
(c – Velocity of light)
A ( cdot mathrm{c}^{2} / mathrm{v}^{2} )
B ( cdot 2 c^{2} / v^{2} )
c. ( c^{2} / 2 v^{2} )
D. none
12
1159 The unit of reduction factor of tangent galvanometer is
A. Ampere
B. Gauss
c. Radian
D. No units
12
1160 Under what conditions permanent
electromagnet is obtained if a current carrying solenoid is used? Support your answer with the help of a labelled circuit diagram.
12
1161 If the galvanometer reading is zero in the gives circuit, the current passing through resistance ( 250 Omega ) is
A . 0.016 A
B. 0.16 A
( c cdot 0.032 mathrm{A} )
D. 0.042 A
12
1162 A wire loop ( P Q R S ) formed by joining
two semi-circular wires of radii ( boldsymbol{R}_{1} ) and
( R_{2} ) carries a current ( I ) as shown in the
following diagram. The magnetic
induction at the centre ( O ) is
A ( cdot frac{mu_{0} I}{4 R_{1}} )
в. ( frac{mu_{0} I}{4 R_{2}} )
c. ( frac{mu_{0}}{4 pi} Ileft(frac{1}{R_{1}}-frac{1}{R_{2}}right) )
D ( cdot frac{mu_{0}}{4} Ileft(frac{1}{R_{1}}+frac{1}{R_{2}}right) )
12
1163 Assertion
Magnetic force on a moving charge is always perpendicular to the magnetic field.
Reason
Electric force on a charge is along the direction of electric field.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
1164 A given length of wire can be bent to form a circle or a square of single turn and a current may be established in it. The ratio of magnetic field at the centre of circle to that at the centre of square is :
A ( cdot frac{pi^{2}}{8 sqrt{2}} )
B. ( frac{4 sqrt{2}}{pi^{2}} )
c. ( frac{pi}{2 sqrt{2}} )
D.
12
1165 Which of the following is likely to have the largest resistance?
A. Voltmeter of range 10 v
B. Moving coil galvanometer
c. Ammeter of range 1 A
D. A copper wire of length ( 1 mathrm{m} ) and diamete
12
1166 A magnetizing field of ( 1600 mathrm{A} / mathrm{m} ) producers a magnetic flux of ( 2 times 10^{-5} ) Wh in a bar of iron of cross section ( 0.2 x )
( 10^{-4} m^{2} . ) Calculate the susceptibility of
the bar.
A . 596.8
B . 288.9
( c cdot 2 )
D. 1328
12
1167 Which of the following figures
represents the magnetic lines of force
due to an isolated north pole?
( A )
B.
( c . ) Both
D. None
12
1168 A proton travels few distance in an
electric field, then it enters a crossed
magnetic field of ( 1 mathrm{T} ) and radius ( 0.2 mathrm{m} ) Find the velocity of proton.
A ( cdot 0.2 times 10^{8} mathrm{ms}^{-1} )
В. ( 0.2 times 10^{7} mathrm{ms}^{-1} )
( c cdot 0.2 times 10^{6} m s^{-1} )
( – )
D. ( 2 times 10^{8} mathrm{ms}^{-1} )
12
1169 Two circular coils of radii ( 5 mathrm{cm} ) and 10
cm carry currents of 2 A.The coils have 50 and 100 turns respectively and are placed in such a way that their planes as well as their centres
coincide.Magnitude of magnetic field at the common centre of coil is
This question has multiple correct options
A. ( 8 pi times 10^{-4} T ) if currents in the coils are in same ser
B . ( 4 pi times 10^{-4} T ) if currents in the coils are in opposite
sense
c. zero if currents in the coils are in opposite sense
D. ( 8 pi times 10^{-4} T ) if currents in the coils are in opposite
sense
12
1170 Show that in an ideal toroid the
magnetic field outside the toroid at any point in the open space is zero.
12
1171 In order to increase the sensitivity of a moving coil galvanometer:
A. the magnetic field should be increased
B. the suspension wire should be made stiff.
c. the area of the coil should be reduced
D. the number of turns in the coil should be reduced
12
1172 Two parallel conductors ( P ) and ( Q ) of equal lengths carry currents I and ( 5 I ) respectively in the same direction, then.
A. They will repel each other with the same force
B. They will attract each other with the same force
c. A will attract but B will repel
D. B will attract but A will repel
12
1173 Figure below shows two infinitely long
and thin current carrying conductors ( boldsymbol{X} )
and ( Y ) kept in vacuum, parallel to each
other, at a distance ‘a
Define ampere, in terms of force
between two current carrying
conductors
12
1174 In a tangent galvanometer a current of
( 0.1 A ) produces a deflection of ( 30^{circ} . ) The
current required to produced a
deflection of ( 60^{circ} ) is
A . ( 0.2 A )
в. ( 0.3 A )
( c .0 .4 A )
D. ( 0.5 A )
12
1175 In terms of potential difference ( V )
electric current I, permittivity ( varepsilon_{0} )
permeability ( mu_{0} ) and speed of light ( c, ) the dimensionally correct equation(s) is(are).
This question has multiple correct options
A ( cdot mu_{0} I^{2}=varepsilon_{0} V^{2} )
В ( cdot varepsilon_{0} I=mu_{0} V )
c. ( I=varepsilon_{0} c V )
D. ( mu_{0} c l=varepsilon_{0} V )
12
1176 Two very long, straight wires carrying currents as shown in figure. Find all locations where the net magnetic field is zero
( y=sqrt{2} x )
( x )
в. ( y=x )
c. ( y=-x )
D. ( y=-(x / 2) )
12
1177 Ampere rule is used to find the
A. direction of current
B. direction of magnetic field
C. direction of motion of the conductor
D. magnitude of current
12
1178 Which of the following is true for a toroid?
A. low inductance and ( Q ) factor
B. high inductance and Q factor
c. high inductance and low ( mathrm{Q} ) -factor
D. low inductance and high ( mathrm{Q} ) -factor
12
1179 In the shown figure a current 2i is
flowing in a straight conductor and entering along the diameter of the
circular loop of similar conductor
through the point A. The current is leaving the loop along another similar
semi-infinite conductor parallel to the plane of the loop through the other opposite end D of the diameter.
12
1180 The dipole moment of a current loop is independent of
A. current in the loop
B. number of turns
c. area of the loop
D. magnetic field in which it is situated
12
1181 A long wire carries a current of ( 20 A )
long the axis of a solenoid, the field due to the solenoid is 4 mT. The resultant
field at a point 3 mm from the solenoid
axis is :
A. ( 1.33 mathrm{mT} )
в. ( 4.2 mathrm{mT} )
c. ( 2.1 m T )
D. ( 8.4 mathrm{mT} )
12
1182 Let ( left[varepsilon_{o}right] ) denote the dimensional formula
of the permittivity of the vacuum, and
( left[mu_{o}right] ) that of the permeability of the vacuum. If ( mathrm{M}= ) mass, ( mathrm{L}= ) length, ( mathrm{T}= ) time
and I = electric current.
This question has multiple correct options
A ( cdotleft[mu_{o}right]=M^{-1} L^{-3} T^{2} I )
B . ( left[varepsilon_{o}right]=M^{-1} L^{-3} T^{4} I^{2} )
c. ( left[mu_{o}right]=M L T^{-2} I^{-2} )
( mathbf{D} cdotleft[mu_{o}right]=M L^{2} T^{-1} I )
12
1183 Assertion: When radius of a circular wire
carrying current is doubled, its magnetic
moment becomes four times
Reason: Magnetic moment is
directly proportional to area of the loop
A. Both A and R are true and R is the correct explanation of A.
B. Both ( A ) and ( R ) are true and ( R ) is not correct explanation of A.
C. ( A ) is true, but ( R ) is false
D. A is false, but R is true
12
1184 Ratio of electric and magnetic field due to moving point charge if its speed is
( 4.5 times 10^{5} mathrm{m} / mathrm{s} )
A ( .2 times 10^{1} )
B . ( 3 times 10^{11} )
( c cdot 2 times 10^{8} )
D. ( 3 times 10^{12} )
12
1185 A wire carrying a current of ( 5 mathrm{A} ) is placed perpendicular to a magnetic induction of 2T.The force on each centimeter of the
wire is
A . ( 0.1 mathrm{N} )
B. 10 N
( c cdot 100 N )
D. 1 N
12
1186 In Fleming’s left hand rule, thumb shows direction of
A. current
B. Field
c. Motion
D. charge
12
1187 Two wires are pictured below, both
carrying current toward the east. What is the direction of the force exerted by
wire 2 on wire ( 1 ? )
North
West
A. north
B. south
c. up
D. down
E. east
12
1188 The magnetic moment of an electron
with orbital angular momentum ( boldsymbol{J} ) will
be:
( ^{mathbf{A}} cdot frac{e vec{J}}{m} )
B. ( frac{e vec{J}}{2 m} )
c. ( frac{2 m}{e bar{J}} )
D. zero
12
1189 Find out the following in the electric
circuit given in Figure.

Difference in reading of ammeter ( boldsymbol{A}_{mathbf{1}} )
and ( A_{2}(text { if any }) )

12
1190 A wire is placed to the lines of force in a
magnetic field and a current flows in
the wire. Then
A. the wire will experience a force in the direction of magnetic field
B. the wire will not experience any force at all
C. the wire will experience a force in a direction opposite to the field
D. it experiences a force in a direction perpendicular to lines of force
12
1191 A long solenoid has 200 turns per cm
and carries a current ( I ). The magnetic
field at its centre is ( 6.28 times )
( 10^{-2} W b / m^{2} . ) Another long solenoid has
100 turns per cm and it carries a
current ( I / 3 . ) The value of the magnetic
field at its centre is
A ( cdot 1.05 times 10^{-2} mathrm{Wb} / mathrm{m}^{2} )
B . ( 1.05 times 10^{-5} mathrm{Wb} / mathrm{m}^{2} )
c. ( 1.05 times 10^{-3} mathrm{Wb} / mathrm{m}^{2} )
D. ( 1.05 times 10^{-4} mathrm{Wb} / mathrm{m}^{2} )
12
1192 Two circular coils made up of identical
wires of length ( 40 mathrm{cm} ) have respectively 8 and 4 turns and the current flowing through the second coil is 4 times
greater than in the first coil. The ratio of magnetic induction at their centres is :
A . 2: 3
B. 3:
( c cdot 1: )
D. 1: 2
12
1193 A proton and an ( alpha ) -particle, accelerated through the same potential difference, enter a region of uniform magnetic field normally. If the radius of the proton orbit is ( 10 c m, ) the radius of ( alpha ) -orbit is
( mathbf{A} cdot 10 mathrm{cm} )
в. ( 10 sqrt{2} mathrm{cm} )
( c cdot 20 c m )
( D .5 sqrt{2} c m )
12
1194 A current-carrying wire in a magnetic field is subject to a magnetic force. If the current in the wire is doubled, what
happens to the magnetic force acting on the wire?
A. It is quartered
B. It is halved
c. It is unchange
D. It is doubled
E. It is quadrupled
12
1195 The radius of the curved part of the wire is ( R=100 m m, ) the linear parts of the
wire are very long. Find the magnetic induction at the point ( O ) if the wire
carrying a current ( I=8.0 A ) has the
shape shown in figure.
A ( .0 .34 mu T )
в. ( 0.11 mu T )
c. ( 1.1 mu T )
D. ( 34 mu ) 7
12
1196 What can be the causes of helical
motion of a charged particle?
12
1197 A current ( I ) flows in a long single-layer
solenoid with cross-sectional radius ( boldsymbol{R} )
The number of turns per unit length of
the solenoid equals ( n ). If the limiting current at which the winding
may rupture if the tensile strength of
the wire is equal to ( boldsymbol{F}_{text {lim }} ) is ( boldsymbol{I}_{text {lim }}= ) ( sqrt{frac{x F_{l i m}}{mu_{0} n R}} . ) Find ( x )
12
1198 Two straight wires ( A ) and ( B ) of lengths 10m and 12m carrying currents of 4.0 A and 6.0 A respectively in opposite direction, lie parallel to each other at a distance of ( 3.0 mathrm{cm} . ) The force on a ( 15 mathrm{cm} )
section of the wire ( mathrm{B} ) near its centre is
A. 2.4 ( times 10^{-5} N ), attractive
B. 2.4 ( times 10^{-5} N ), repulsive
C. ( 1.2 times 10^{-5} N ), attractive
D ( cdot 1.2 times 10^{-5} N, ) repulsive
12
1199 Potential energy of a current loop placed inside some magnetic field does not depend upon magnetic moment of the
loop.Enter 1 if True and 0 if False.
12
1200 Ampere’s circuital law is given by:
A ( cdot oint bar{H} cdot overline{d l}=mu_{0} I_{e n c} )
B . ( oint bar{B} . overline{d l}=mu_{0} I_{e n c} )
( mathbf{c} cdot oint bar{B} cdot bar{d} l=mu_{0} I )
D . ( oint bar{H} . overline{d l}=mu_{0} I )
12
1201 A straight magnetised wire of magnetic
moment ‘ ( M^{prime} ) is bent as shown. Find
resultant magnetic moment in each
case.
12
1202 An electron of charge e and mass ( mathrm{m} ) is moving in circular path of radius r with a uniform angular speed. Then which of the following statements are correct? This question has multiple correct options
A. The equivalent current flowing in the circular path is proportional to ( r^{2} )
B. The magnetic moment due to circular current loop is independent of
C. The magnetic moment due to circular current loop is equal to ( 2 mathrm{e} / mathrm{m} ) time the angular momentum of the electron
D. The angular momentum of the particle is proportional to the areal velocoty of electron.
12
1203 Two long wires are hanging freely. They are joined first in parallel and then in
series and then are connected with a
battery. In both cases which type of force acts between the two wires?
A. Attraction force when in parallel and repulsion force when in series
B. Repulsion force when in parallel and attraction force when in series
c. Repulsion force in both cases
D. Attraction force in both cases
12
1204 Which of the following effects of current
does not depend on the direction of
current?
A. Lighting and chemical effects
B. Heating and lighting effects
c. Heating and magnetic effects
D. Magnetic and chemical effects
12
1205 A galvanometer of 50 gives full scale
deflection with 2 mA current as to
convert it into ammeter range of 10 A is connected with it then shunt resistance
will be
A . ( 0.1 Omega )
B. ( 0.2 Omega )
c. ( 0.01 Omega )
D. ( 0.001 Omega )
12
1206 Two long thin parallel conductor are
kept very close to each other without
touching. One carries a current ( i ) and
the other has charge ( lambda ) per unit length. An electron moving parallel to the
conductor is undeflected. If ( c ) is the
velocity of light. then :
This question has multiple correct options
A ( cdot v=frac{lambda c^{2}}{i} )
B. ( v=frac{i}{lambda} )
c. ( c=frac{i}{lambda} )
D. the electron may be at any distance from the conductor
12
1207 Two long parallel wires ( P ) and ( Q ) are held
perpendicular to the plane of the paper at a acceptance of ( 5 mathrm{m} ) between them. If ( P )
and ( Q ) carry currents of 2.5 and 5 amp
respectively in the same direction, then
the magnetic field at a point half way
between the wire is
( mathbf{A} cdot frac{mu_{0}}{pi} )
B. ( frac{sqrt{3} mu_{0}}{pi} )
( c cdot frac{mu_{0}}{2 pi} )
D. ( frac{3 mu_{0}}{2 pi} )
12
1208 A thin conducting strip of width ( h= ) ( 2.0 mathrm{cm} ) is tightly wound in the shape of
a very long coil with cross-section radius ( R=2.5 mathrm{cm} ) to make a single-
layer straight solenoid. A direct current ( boldsymbol{I}=mathbf{5 . 0} boldsymbol{A} ) flows through the strip. Find
the magnetic induction inside and
outside the solenoid as a function of the
distance ( r ) from its axis.
12
1209 A long solenoid has 200 turns per ( mathrm{cm} ) and carries a current ( i . ) The magnetic
field at its centre is ( 6.28 times ) ( 10^{-2} W b m^{-2} . ) Another solenoid has 100
turns per ( c m ) and it carries a current ( frac{i}{3} ) The value of the magnetic field at its
centre :
A . ( 1.05 times 10^{-4} mathrm{Wbm}^{-2} )
B. ( 1.05 times 10^{-2} mathrm{Wbm}^{-2} )
c. ( 1.05 times 10^{-5} mathrm{Wbm}^{-2} )
D. ( 1.05 times 10^{-3} mathrm{Wbm}^{-2} )
12
1210 A rectangular loop of wire is oriented with the left corner at the origin, one edge along X-axis and the other edge along Y-axis as shown in the figure. A magnetic field is into the page and has
a magnitude that is given by ( beta=alpha y )
where ( alpha ) is constant. Find the total
magnetic force on the loop if it carries
current ( i )
12
1211 Biot-Savart law indicates that the
moving electrons (velocity ( overline{boldsymbol{v}} ) ) produce a magnetic field ( bar{B} ) such that:
( mathbf{A} cdot bar{B} perp bar{v} )
B . ( bar{B} | bar{v} )
C . it obeys inverse cube law.
D. it is along the line joining the electron and point of observation.
12
1212 A current ( i ) ampere flows along an infinitely long straight thin walled tube, then the magnetic induction at any
point inside the tube is
( A cdot infty )
в. zero
c. ( frac{mu_{0}}{4 pi} cdot frac{2 i}{r} ) tesla
D. ( frac{2 i}{r} ) tesla
12
1213 A circular loop of wire has current going
through it in the clockwise direction.
What is the direction of the magnetic
field that is caused by this current
through the wire?
A. Inside the loop: out of the screen
Outside the loop: into the screen
B. Inside the loop: out of the screen
Outside the loop: out of the screen
C. Inside the loop: into the screen
Outside the loop: out of the screen
D. Inside the loop: into the screen
Outside the loop: into the screen
12
1214 You are provided with one low
resistance ( R_{L} ) and one high resistance
( R_{H} ) and two galvanometers. One
galvanometer is to be converted to an ammeter and the other to a voltmeter.
Show how you will do this with the help of simple, labelled diagrams
12
1215 A galvanometer having a resistance of ( 120 Omega ) is shunted by ( 5 Omega ) resistance.
What is the ratio of current in shunt to
the current in galvanometer?
12
1216 A long solenoid has 200 turns per cm
and carries a current i.The magnetic field at its centre is ( 6.28 times ) ( 10^{-2} W b / m^{2} . ) Another long solenoid
has 100 turns per ( mathrm{cm} ) and it carries a
current i/3.The value of magnetic field
at its centre is:
A ( cdot 1.05 times 10^{-2} mathrm{Wb} / mathrm{m}^{2} )
в. ( 1.05 times 10^{-5} mathrm{Wb} / mathrm{m}^{2} )
c. ( 1.05 times 10^{-3} mathrm{Wb} / mathrm{m}^{2} )
D. ( 1.05 times 10^{-4} mathrm{Wb} / mathrm{m}^{2} )
12
1217 State and explain Ampere’s circuital
law.
12
1218 On what factors does the force
experienced by a current carrying conductor placed in a uniform magnetic field depend?
A. Magnetic field
B. current
c. Length of the conductor
D. All
12
1219 Compare the magnetic field produced by a solenoid with that of bar magnet by drawing respective diagrams. 12
1220 Draw the magnetic field lines due to a current passing through a long solenoid. Use Ampere’s circuital law, to obtain the expression for the magnetic field due to the current I in a long solenoid having n number of turns per unit length. 12
1221 The force experience by charged ‘q’ moving with velocity with ‘v’ in magnetic filled be is given by ( mathrm{F}=mathrm{qvB} ) Find the dimension of mag field. 12
1222 Two circular coil 1 and 2 are made from
the same wire but the radius of the 1 st
coil is twice that of the ( 2 n d ) coil. What
potential difference in volts should be applied across them so that the magnetic field at their centres is
the same-
A . 3
B. 4
( c cdot 6 )
D. 2
12
1223 A charged particle is projected in a plane perpendicular to uniform magnetic field. The areal velocity (area swept per unit time) of the particle is :
This question has multiple correct options
A. directly proportional to kinetic energy of particle
B. directly proportional to momentum of the particle
c. inversely proportional to magnetic field strength
D. inversely proportional to charge on particle
12
1224 Particles having positive charge occasionally come with high velocity from the sky towards the earth on account of magnetic field of earth, they would be deflected towards:
A. North
B. South
( c . ) East
D. west
12
1225 The magnetic field due to a current carrying circular loop of radius ( 3 mathrm{m} ) at a point on the axis at a distance of ( 4 mathrm{m} )
from the centre is ( 54 mu T . ) What will be its
value at the centre of the loop?
A. ( 250 mu T )
в. ( 150 mu T )
c. ( 125 mu T )
D. ( 75 mu T )
12
1226 A magnetic field of ( 100 mathrm{G}left(1 mathrm{G}=10^{-4} mathrm{T}right) ) is required which is uniform in a region of linear dimension about ( 10 mathrm{cm} ) and area
of cross-section about ( 10^{-3} m^{2} . ) The
maximum current-carrying capacity of a given coil of wire is 15 A and the
number of turns per unit length that can be wound round a core is at most
1000 turns ( m^{-1} . ) Suggest
some appropriate design particulars of a solenoid for the required purpose. Assume the core is not ferromagnetic.
12
1227 What are the units of magnetic moments and magnetic induction? 12
1228 If ( 2 % ) of the main current is to be
passed through a galvanometer of resistance ( G ), then resistance of the
shunt required is
A ( cdot frac{G}{50} )
в. ( frac{G}{49} )
c. ( 49 G )
D. ( 50 G )
12
1229 If the direction of the current changes in the current carrying loop placed in some magnetic field perpendicular to loop, then Potential energy of loop is not effected because current is a scalar
quantity.Enter 1 if true and 0 if False.
12
1230 In cyclotron the charged particle may be accelerated upto energies
A. several ev
B. Mev
c. Bev
D. Kev
12
1231 Match the following.
( mathbf{A} cdot A-H, B-G, C-E, D-F )
( mathbf{B} cdot A-G, B-H, C-E, D-F )
( mathbf{c} cdot A-E, B-H, C-G, D-F )
( mathbf{D} cdot A-F, B-G, C-H, D-F )
12
1232 If a charged particle is projected perpendicular to uniform magnetic
field, then
a) force experienced will be perpendicular to the magnetic field and
initial velocity.
b) force experienced will be perpendicular to the magnetic field and instantaneous velocity
c) the work done by the magnetic field
is zero.
d) the particle experiences both radial and tangential accelerations.
A. a, b, c are correct d is wrong
B. all are correct
c. a, b are correct, c, d are wrong
D. a, b, c are wrong, d is correct
12
1233 A solenoid of ( 0.4 mathrm{m} ) length with 500 turns carries a current of ( 3 mathrm{A} ). A coil of 10
turns and of radius ( 0.01 mathrm{m} ) carries a
current of 0.4 A. The torque required to hold the coil with its axis at right angle to that of the solenoid in the middle part
of it, is:
A ( cdot 6 pi^{2} times 10^{-7} N m )
В. ( 3 pi^{2} times 10^{-7} mathrm{Nm} )
c. ( 9 pi^{2} times 10^{-7} N m )
D. ( 12 pi^{2} times 10^{-7} mathrm{Nm} )
12
1234 The magnetic induction due to circular current-carrying conductor of radius ( a )
at its centre is ( B_{c} ). The magnetic
induction on its axis at a distance ( a )
from its centre is ( B_{a} . ) The value of ( B_{c}: )
( boldsymbol{B}_{boldsymbol{a}} ) will be :
A ( cdot sqrt{2}: 2 )
B. ( 1: 2 sqrt{2} )
c. ( 2 sqrt{2}: 1 )
D. ( 2: sqrt{2} )
12
1235 Q Type your question.
( n=v ) an with its centre al origin.
Current ( I=1 A ) is lead to the sphere in
one of the wires lying (on y-axis) and in the other wire (on x-axis) it is lead away
from the sphere. A uniform and
constant external magnetic field
exists in positive z-direction and has
magnitude ( B_{o}=2 T . ) Then find the
magnitude of magnetic force
(in newtons) on the solid sphere due to
external magnetic field.
( A )
B. 4
( c .5 )
( D )
12
1236 A copper wire of cross sectional area
( 3 m m^{2} ) carrying a current of ( 4 A ) has ( 10^{29} ) free electrons ( / m^{3} . ) If this wire is
now placed in a field of induction ( 0.15 T ) perpendicular to wire. The force on each electron is :
A . ( 20 times 10^{-25} mathrm{N} )
В. ( 37.5 times 10^{-25} N )
( begin{array}{ll}text { С } & 10 times 10^{-25} Nend{array} )
D. ( 41.7 times 10^{-25} N )
12
1237 A long straight wire of radius R carries a current distributed uniformly over its cross-section. The magnitude of the magnetic field is This question has multiple correct options
A. maximum at the axis of the wire
B. minimum at the axis of the wire
c. maximum at the surface of the wire
D. minimum at the surface of the wire
12
1238 begin{tabular}{l}
( E ) \
( L ) \
( L ) \
hline
end{tabular}
12
1239 A solenoid of length ( 1.5 m ) and ( 4 c m ) in
diameter possesses 10 turns per metre. A current of ( 5 A ) is flowing
through it. The magnetic induction at a point inside the solenoid along the axis
is ( _{-}——left(mu_{0}=4 pi timesright. )
( mathbf{1 0}^{-mathbf{7}} boldsymbol{W b} / mathbf{A . m} )
A ( cdot pi times 10^{-5} T )
В. ( 2 pi times 10^{-5} T )
c. ( 3 pi times 10^{-5} T )
D . ( 4 pi times 10^{-5} T )
12
1240 A coil of metal wire is kept stationary in a non-uniform magnetic field. An emf is induced in the coil.
A. True
B. False
12
1241 Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is
deflected by strong magnetic field to your right side. What is the direction of
magnetic field?
12
1242 Two long parallel conductors are placed
at right angles to a metre scale at the ( 2 c m ) and ( 4 c m ) marks, as shown in the
figure. They carry currents of ( 1 A ) and ( 3 A )
respectively. They will produce zero magnetic field at the
(ignore the Earth’s magnetic field)
A. ( 0.5 mathrm{cm} ) mark
B. ( 2.5 mathrm{cm} ) mark
c. ( 1 mathrm{cm} ) mark
D. ( 8 mathrm{cm} ) mark
12
1243 To know the resistance ( G ) of a
galvanometer by half deflection method,
a battery of emf ( V_{E} ) and resistance ( R ) is
used to deflect the galvanometer by
angle ( theta . ) If a shunt of resistance ( S ) is
needed to get half deflection the ( G, R ) and ( S ) are related by the equation:
A. ( S(R+G)=R G )
B. ( 2 S(R+G)=R G )
( mathrm{c} cdot 2 G=S )
D. ( 2 S=G )
12
1244 A rectangular coil of 500 turns and of
( operatorname{area} 6 times 10^{-4} m^{2} ) is suspended inside a
radial magnetic field of induction
( 10^{-4} T ) by a suspension wire of torsional constant ( 5 times 10^{-10} N m ) per degree
Calculate the current required to
produce a deflection of ( 10^{circ} )
12
1245 Proton, denteron and alpha particles of the same kinetic energy and moving in circular trajectories in a constant magnetic field. The radii of proton, denteron and alpha particles are
respectively ( r_{p}, r_{d} ) and ( r_{alpha} . ) Which one of the following relations is correct?
A ( cdot r_{alpha}=r_{p}=r_{d} )
B . ( r_{alpha}=r_{p}r_{d}>r_{p} )
D ( cdot r_{alpha}=r_{d}>r_{p} )
12
1246 The value of intensity of magnetic field at a point due to a current carrying conductor depends
A. on the value of current
B. On a small part of length of conductor
c. on angle between the line joining the given point to the mid point of small length and the distance between the small length of the point
D. On all and the above
12
1247 In the adjacent circuit a resistance ( mathrm{R} ) is
used. Initially with ‘wire ( A B^{prime} ) not in the
circuit, the galvanometer shows a deflection of d divisions. Now, the ‘wire
( A B^{prime} ) is connected parallel to the
galvanometer and the galvanometer shows a deflection nearly ( boldsymbol{d} / 2 ) division. Therefore current sensitivity of the galvanometer is about:
12
1248 In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will
be a
A. helix
B. straight line
c. ellipse
D. circle
12
1249 Two ( 2 mathrm{m} ) long parallel wires are placed in vacuum at a distance ( 0.2 mathrm{m} ). If
current ( 0.2 mathrm{A} ) flows in both the wires in
the same direction, calculate the force acting per unit length between them.
12
1250 Write an underlying principle of the moving coil galvanometer? 12
1251 A wire lying along y-axis from ( y=0 ) to ( y=1 ) m carries a current of ( 2 mathrm{mA} ) in the
negative y-direction.The wire lies in a non-uniform magnetic field given by ( vec{B}=(0.3 T / m) y hat{i}+(0.4 T m) y hat{j} . ) The
magnetic force on the entire wire is
A ( cdot-3 times 10^{-4} hat{j} N )
В. ( 6 times 10^{-3} hat{k} N )
c. ( -3 times 10^{-4} hat{k} N )
D. ( 3 times 10^{-4} hat{k} N )
12
1252 Give two characteristics of magnetic field lines. 12
1253 The magnetic field produced by a current-carrying wire at a given point depends on
A. the current passing through it
B. the voltage across it
c. the power through it
D. all
12
1254 A solenoid is a coil of insulated or
enameled wire wound on a rod-shaped
form made of solid iron, solid steel, or
powdered iron.

State whether this statement is true or
false.
Write 1 for True and 2 for False

12
1255 Maximum P.E. of magnet of moment M situated in a magnetic field of induction
( mathrm{B}, ) is
( ^{mathbf{A}} cdot frac{1}{2} M B )
в. ( frac{M}{B} )
( mathbf{c} .2 M B )
D. ( M B )
12
1256 In a cyclotron, magnetic field of ( 3.5 W b / m^{2} ) is used to accelerate
protons.What should be the time interval in which the electric field
between the Dees be reversed?
(Mass of proton ( =1.67 times 10^{-27} k g )
charge on proton ( =mathbf{1 . 6} times mathbf{1 0}^{-mathbf{1 9}} mathbf{C} ) ).
12
1257 The magnetic moment of a bar magnet is
0.256 amp.m ( ^{2} ). Its pole strength is 400
milli amp. m. It is cut into two equal
pieces and these two pieces are arranged
at right angles to each other with their unlike poles in contact (or like poles in contact). The resultant magnetic
moment of the system is
A ( cdot sqrt{2} times 256 times 10^{-3} A m^{2} )
B . ( 250 times 10^{-3} mathrm{Am}^{2} )
c. ( frac{256}{sqrt{2}} times 10^{-3} mathrm{Am}^{2} )
D ( cdot frac{128}{sqrt{2}} times 10^{-3} mathrm{Am}^{2} )
12
1258 A uniformly charged ring of radius R carrying q is rotating with angular speed ( omega . ) The magnetic field at the centre of ring is:
A ( cdot frac{mu_{o} q omega}{2 pi R} )
в. ( frac{mu_{0} q omega}{4 pi R} )
c. ( frac{mu_{q} q omega}{8 pi R} )
D. zero
12
1259 Assertion
Amperes circuital law holds for steady
currents which do not fluctuate with
time.
Reason
Amperes circuital law is similar to that
of Biot-savarts law.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
1260 A long solenoid is fabricated to closely winding wire of radius ( 0.5 mathrm{mm} ) over a cylinderical frame, so that the
successive turns nearly touch each other. The magnetic field at the centre of solenoid, if it carries a current of 5 A
is?
( mathbf{A} cdot 2 pi times 10^{-2} mathbf{T} )
В . ( 2 pi times 10^{-3} mathrm{T} )
с. ( 2 pi times 10^{-4} mathrm{T} )
D. ( 2 pi times 10^{-5} mathrm{T} )
12
1261 A current of 3 A is flowing in a linear conductor having a length of ( 40 mathrm{cm} . ) The conductor is placed in a magnetic field
of strength 500 gauss and makes an
angle ( 30^{circ} ) with the direction of the field.
It experiences a force of magnitude
( mathbf{A} cdot 3 times 10^{-4} N )
B. ( 3 times 10^{-2} N )
c. ( 3 times 10^{2} N )
D. ( 3 times 10^{4} N )
12
1262 A magnet of magnetic moment 20 CGS units is freely suspended in a uniform magnetic field of intensity ( 0.3 mathrm{CGS} ) units. The moment of work done in
deflecting it by an angle of ( 30^{circ} ) in ( C G S )
units is
A . 6
B. ( 3 sqrt{3} )
c. ( 3(2-sqrt{3}) )
D. 3
12
1263 Two wires of same length are shaped into square and a circle. if they carry same current ratio of magnetic moment is
A . ( 2: pi )
в. ( pi: 3 )
( c cdot pi: 4 )
D. ( 1: pi )
12
1264 A circular coil of radius ( 4 mathrm{cm} ) and of 20
turns carries a current of 3 amperes. It is placed in a magnetic field of intensity
of 0.5 weber ( / m^{2} . ) The magnetic dipole moment of the coil is
A. 0.15 ampere ( -m^{2} )
B. 0.3 ampere ( -m^{2} )
c. 0.45 ampere ( -m^{2} )
D. 0.6 ampere ( -m^{2} )
12
1265 A straight wire of mass ( 200 g ) and length
( 1.5 m ) carries a current of ( 2 A . ) It is
suspended in mid air by a uniform
horizontal magnetic field ( B ). The
magnitude of ( B ) (in tesla) is :
A . 0.65
в. 0.55
c. 0.75
D. 0.45
12
1266 State the underlying principle of a cyclotron. Write briefly how this machine is used to accelerate charged particles to high energies. 12
1267 A helium nucleus makes a full rotation
in a circle of radius ( 0.8 m ) in two
seconds. The value of the magnetic field
B at the centre of the circle will be
( mathbf{A} cdot 10^{-19} / mu_{0} )
B . ( 10^{-19} ) p ( _{0} )
c. ( 2 times 10^{-19} mu_{0} )
D. ( 2 times 10^{-19} / mu_{0} )
12
1268 A current of 0.24 A flows through a
circular coil of 72 turns, the average diameter of the coil being ( 20 mathrm{cm} . ) What is the strength of field produced at the centre of the coil?
12
1269 The pole is pieces of a horse-shoe magnet are made cylindrical so that the deflection of the coil is proportional to
A. the current flowing in the coil
в. ( frac{1}{text { current flowing in the coil }} )
c. the magnetic field
D. the square of current flowing in the coil
12
1270 Two conductors each of length ( 12 m ) lie
parallel to each other in air. The centre
to centre distance between the two
conductors is ( 15 times 10^{-2} m ) and the
current in each conductor is ( 300 A ). The
force in newton tending to pull the conductors together is:
A . ( 14.4 N )
B. ( 1.44 N )
c. ( 144 N )
D. ( 0.144 N )
12
1271 A current ( I=1.00 A ) circulates in a
round thin-wire loop of radius ( boldsymbol{R}= )
100 ( m m ). Find the magnetic
induction at the centre of the loop.
A. ( 7.3 mu T )
B. ( 3.7 mu T )
c. ( 3.6 mu T )
D. ( 6.3 mu T )
12
1272 A particle is moving with velocity ( vec{v}= ) ( hat{mathbf{i}}+mathbf{3} hat{mathbf{j}} ) and it produces an electric field at that point equal to ( 2 hat{k} ), find the magnetic field at that point (all) quantities are in Sl units)
A ( cdot(6 hat{i}-2 hat{j}) mu_{0} varepsilon_{0} )
B . ( (6 hat{i}+2 hat{j}) mu_{0} varepsilon_{0} )
c. zero
D. cannot be determined from the given data
12
1273 A charged particle of unit mass and
unit charge moves with velocity ( vec{v}= ) ( (8 hat{i}+6 hat{j}) m s^{-1} ) in a magnetic field of ( vec{B}=2 hat{k} T . ) Choose the correct
alternative(s).
This question has multiple correct options
A ( cdot ) the path of the particle may be ( x^{2}+y^{2}-4 x-21=0 )
B. the path of the particle may be ( x^{2}+y^{2}=25 )
c. the path of the particle may be ( y^{2}+z^{2}=25 )
D. the time period of the particle will be 3.14 s
12
1274 The radius of the curved part of the wire
is ( R, ) the linear parts are assumed to be
very long. Find the magnetic induction
of the field at the point ( O ) if a current-
carrying wire has the shape shown in figure above.
( ^{mathbf{A}} cdot B=frac{mu_{0}}{4 pi} frac{I}{R}left[1+frac{3 pi}{2}right] )
в. ( B=frac{mu_{0}}{pi} frac{I}{R}left[1+frac{3 pi}{2}right] )
c. ( _{B}=frac{mu_{0}}{2 pi} frac{I}{R}left[1+frac{3 pi}{2}right] )
D. ( B=0 )
12
1275 A moving charge will produce
A. No field
B. An electric field only
C. A magnetic field only
D. Both (b) and (c)
12
1276 The electric permittivity nad magnetic
permeability of free space are ( varepsilon_{0} ) and ( mu_{0} ) respectively. The index of refraction of
the medium, if ( varepsilon ) and ( mu ) are the electric
permittivity and magnetic permeability in a medium is :
A ( cdot frac{varepsilon mu}{varepsilon_{0} mu_{0}} )
( ^{text {В }}left(frac{varepsilon mu}{varepsilon_{0 mu_{0}}}right)^{1 / 2} )
c. ( frac{varepsilon_{0} mu_{0}}{varepsilon_{mu}} )
( ^{mathrm{D}}left(frac{varepsilon_{0} mu_{0}}{varepsilon mu}right)^{1 / 2} )
12
1277 Write the definition of figure of merit of
Galvanometer.
12
1278 Electrons traveling at a velocity of
( 2.4 times 10^{6} m s^{-1} ) enter a region of cross
electric and magnetic fields as shown in fig. If the electric field is ( 3.0 x )
( 10^{6} V m ) and the flux density of the
magnetic field is ( 1.5 mathrm{T} ), the electron upon
entering the region of the crossed fields
will
A. continue to travel undeflected in their original direction
c. be deflected downward on the plane of the diagram
D. none of the above
12
1279 An electric current through a metallic conductor produces around it.
A. Magnetic field
B. Mechanical force
c. Induced current
D. None
12
1280 A vertical wire carrying current in the downward direction is placed in a horizontal magnetic field directed northwards. The direction of the force on
the wire is
A. Eastward
c. Upwards
D. Westward
12
1281 Find the mobility of the conduction electrons in a copper conductor if in Hall effect measurements performed in the magnetic field of induction ( boldsymbol{B}= )
100 ( m T ) the transverse electric field
strength of the given conductor turned out to be ( eta=3.1 times 10^{3} ) less than that of
the longitudinal electric field.
12
1282 If ( mu_{0} ) is absolute permeability of
vacuum and ( mu_{r} ) is relative magnetic permeability of another medium, then permeability ( mu ) of the medium is
A . ( mu_{0} mu_{r} )
B. ( mu_{0} / mu_{r} )
( mathbf{c} cdot mu_{r} / mu_{0} )
D. ( I / mu_{0} mu_{r} )
12
1283 In the given arrangement, the loop is moved with constant velocity ( v ) in a
uniform magnetic field ( B ) in a restricted
region of width ( a ). The time for which the
emf is induced in the circuit is
A ( -frac{2 b}{v} )
в. ( frac{2 a}{v} )
c. ( frac{(a+b)}{v} )
D.
12
1284 The direction of force on a current
carrying conductor placed in a magnetic field is given by :
A. Fleming’s Left Hand Rule
B. Fleming’s Right Hand Rule
c. End Rule
D. Right Hand Palm Rule
12
1285 A current carrying small loop behaves like a small magnet. If ( A ) be its area and
( M ) its magnetic moment, the current in the loop will be
A. ( M / A )
в. ( A / M )
( c . M A )
D. ( A m^{2} )
12
1286 An electron is projected into a magnetic
field along the lines of force. Then
A. there will be no effect on its motion
B. the electron will travel along a circle and its speed remains unchanged
C. the electron will follow the path of a parabola and its speed will increase
D. the velocity will increase in magnitude but its direction will remain unchanged.
12
1287 Magnetic field at point ( ^{prime} boldsymbol{P}^{prime} ) due to given
current distribution is:
A ( cdot frac{mu_{0} I}{4 pi r}(1+sqrt{2}) odot )
В ( cdot frac{mu_{0} I}{2 pi r}(1+sqrt{2}) odot )
c. ( frac{mu_{0} I}{4 pi r}(1+sqrt{2}) otimes )
D. ( frac{mu_{0} I}{2 pi r}(1+sqrt{2}) otimes )
12
1288 carrying a current ( boldsymbol{I} ) A. Three
circular Amperian loops 1,2 and 3 are
shown by dashed lines. Point ( P ) is an
interior point. Point ( Q ) is an exterior
point. What is the magnetic field due to
the toroid at points ( P ) and ( Q )
respectively?
A . 0,0
В ( cdot 0, mu_{o}, n )
C ( cdot mu_{o} n I, mu_{o} n I )
( mathbf{D} cdot mu_{o} n I, 0 )
12
1289 To obtain maximum intensity of magnetic field at a point the angle between position vector of point and small elements of length of the conductor is
A. 0
в. ( pi / 4 )
c. ( pi / 2 )
D.
12
1290 An electron is moving in a perpendicular magnetic field of strength ( 4 times 10^{-3} T ) with a velocity of
( 4 times 10^{7} m / s . ) The radius of electron path
will be
( mathbf{A} cdot 0.56 m )
B. ( 0.056 m )
( c .56 m )
D. ( 5.6 m )
12
1291 A long circular tube of length ( 10 m ) and
radius ( 0.3 mathrm{m} ) carries a current I along its curved surface as shown. A wire-loop of resistance 0.0005 ohm and of radius 0.1
( mathrm{m} ) is placed inside the tube with its axis coinciding with the axis of the tube. The
current varies as ( boldsymbol{I}=boldsymbol{I}_{0} cos (boldsymbol{3} boldsymbol{0} boldsymbol{0} boldsymbol{t}) )
where ( I_{0} ) is constant. If the magnetic
moment of the loop is ( N mu_{0} I_{0} sin (300 t) )
then ‘N’ is
12
1292 Find the ratio of magnetic dipole moment to angular momentum in a hydrogen like atom:
A ( cdot frac{e}{m} )
B. ( frac{e}{2 m} )
c. ( frac{e}{3 m} )
D. ( frac{2 e}{m} )
E ( cdot frac{3 e}{m} )
12
1293 Which of the following is based on mechanical effect of electric current?
A. AC Dynamo
B. DC Dynamo
c. AC or DC motor
D. Electric Geyser
12
1294 The ends of a coil are connected to a
galvanometer. When current suddenly I starts flowing in a neighbouring circuit, the instantneous deflection in the
galvanometer is ( +7^{circ} . ) If now the coil be
quickly rotate through ( 180^{circ}, ) what will be the maximum deflection in the
galvanometer?
A ( cdot 7^{circ} )
B. ( 14^{circ} )
( c cdot 21^{0} )
( D cdot 28^{circ} )
12
1295 Find the concentration of the
conduction electrons.
A ( cdot 2.5 times 10^{20} mathrm{m}^{-3} )
В. ( 2.5 times 10^{26} mathrm{m}^{-3} )
c. ( 2.5 times 10^{28} mathrm{m}^{-3} )
D. ( 2.5 times 10^{30} m^{-3} )
12
1296 A neutral particle is at rest in a uniform magnetic field ( vec{B} ). At time ( t=0 ) it decays into two charged particles,each of mass
m.The two particles move off in seperate paths,both of them lie in the plane perpendicular to ( vec{B} ). At a later time the
particles collide.Express the time from decay until collison in terms of ( mathrm{m}, mathrm{B} ) and
( mathbf{q} )
12
1297 The current in an ideal, long solenoid is varied at a uniform rate of ( 0.01 A / s . ) The solenoid has 2000 turns/m and its
radius is ( 6.0 mathrm{cm} )
(a) Consider a circle of
radius ( 1.0 mathrm{cm} ) inside the solenoid with its axis coinciding with the axis of the solenoid. Write the change in the magnetic flux through this circle in 2.0 seconds.
(b) Find the electric field
induced at a point on the circumference of the circle.
(c) Find the electric field
induced at a point outside the solenoid
at a distance ( 8.0 mathrm{cm} ) from its axis.
12
1298 An electric current is flowing through a circular coil of radius ( mathrm{R} ). The ratio of the
magnetic field at the center of the coil and that at a distance ( 2 sqrt{2} R ) from the
center of the coil and on its axis is:
12
1299 A solenoid has a core of a substance
with relative permeability ( 600 . ) What is the magnetic permeability of the given substance?
A ( cdot 20 pi times 10^{-5} N A^{-2} )
B. ( 21 pi times 10^{-5} N A^{-2} )
c. ( 22 pi times 10^{-5} N A^{-2} )
D. ( 24 pi times 10^{-5} N A^{-2} )
12
1300 A charged particle is moving through uniform magnetic field, then magnetic
field :
A. Always exerts a force on the particle
B. Never exerts a force on the particle
c. Exerts a force, if the particle is moving along the field.
D. Exerts a force, if the particle is moving perpendicular to the direction of the field
12
1301 Each of the following particles is projected with the same speed into a uniform magnetic field ( B ) such that the particle’s initial velocity is perpendicular to ( B ). Which one would
move in a circular path with the largest radius?

A particle is projected at a given speed into a uniform magnetic field ( B ) and perpendicular to it. Choose the particle that will have the largest radius.
A. Proton
B. Beta particle
c. Alpha particle
D. Electron
E . Positron

12
1302 The ratio of magnetic field at the centre
of a current carrying coil to its
magnetic moment is ( x ). If the current
and radius both are doubled, the new
ratio will become:
A ( .2 x )
B. ( 4 x )
c. ( x / 4 )
D. ( x / 8 )
12
1303 A closely wound solenoid ( 80 mathrm{cm} ) long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8
( mathrm{cm} . ) If the current carried is ( 8.0 mathrm{A} )
estimate the magnitude of B inside the solenoid near its centre :
A ( .1 .5 times 10^{-2} T ), opposite to the axis of solenoid
B . ( 2 times 10^{-2} T ), along the axis of solenoid
C . ( 3.5 times 10^{-2} T ), along the axis of solenoid
D. ( 1.5 times 10^{-2} T ) along the axis of solenoid
12
1304 The value of ( mu_{o} ) is
( mathbf{A} cdot 2 pi times 10^{-7} H m^{-1} )
B ( cdot 4 pi times 10^{-7} mathrm{Hm}^{-1} )
( mathbf{c} cdot 8 pi times 10^{-7} mathrm{Hm}^{-1} )
D ( cdot pi times 10^{-7} mathrm{Hm}^{-1} )
12
1305 What happens to energy when a charged particle moving in a magnetic field although a magnetic force is acting on it?
A . remains constant
B. increases
c. decreases
D. none of these
12
1306 Magnetic lines of force
A. form closed circuits
B. cannot intersect
C . are crowded together near the poles
D. all the above are correct
12
1307 Induced electromotive force in a coil
does not depend on
A. Number of turns in the coil
B. Intensity of the magnetic field
c. Relative speed between coil and the magnet
D. Resistance of the coil
12
1308 A long straight conductor carrying ( boldsymbol{I}_{1} ) is placed in the plane of ribbon at a
distance a from the near edge of a
ribbon of width b, which carries ( boldsymbol{I}_{2} )
parallel to the wire. Find the force of attraction per unit length between the
two.
12
1309 A moving coil galvanometer, having a
resistance ( G ), produces full scale
deflection when a current ( I_{g} ) flows
through it. This galvanometer can be
converted into (i) an ammeter of range
( mathbf{0} operatorname{to} boldsymbol{I}_{mathbf{0}}left(boldsymbol{I}_{mathbf{0}}>boldsymbol{I}_{boldsymbol{g}}right) ) by connecting a shunt
resistance ( boldsymbol{R}_{boldsymbol{A}} ) to it and (ii) into a
voltmeter of range 0 to ( Vleft(V=G I_{0}right) ) by
connecting a series resistance ( boldsymbol{R}_{boldsymbol{V}} ) to it.
Then
( mathbf{A} cdot_{R_{A} R_{V}}=G^{2}left(frac{I_{g}}{I_{0}-I_{g}}right) ) and ( frac{R_{A}}{R_{V}}=left(frac{I_{0}-I_{g}}{I_{g}}right) )
( ^{mathrm{B}} R_{A} R_{V}=G^{2} ) and ( frac{R_{A}}{R_{V}}=left(frac{I_{g}}{I_{0}-I_{g}}right)^{2} )
( ^{mathbf{c}} cdot_{R_{A} R_{V}}=G^{2} ) and ( frac{R_{A}}{R_{V}}=frac{I_{g}}{I_{0}-I_{g}} )
( ^{mathrm{D}} R_{A} R_{V}=G^{2}left(frac{I_{0}-I_{g}}{I_{g}}right) ) and ( frac{R_{A}}{R_{V}}=left(frac{I_{g}}{I_{0}-I_{g}}right)^{2} )
12
1310 A long thin walled hollow cylinder of radius r is carrying a current I. A very long current carrying straight conductor is passing through the axis of the hollow cylinder, carrying a current
( i_{0} . ) Find the tension per unit length developed in the hollow cylinder due to the interaction of the straight current
carrying conductor.
12
1311 A circular coil of wire of ( n ) turns has a
radius ( r ) and carries a current ( i ). Its
magnetic dipole moment is ( M . ) Now the coil is unwound and again rewound into a circular coil of half the initial radius
and the same current is passed through it, then the dipole moment of this new coil is :
A ( cdot frac{M}{2} )
в. ( frac{M}{4} )
c. ( M )
D. 2 ( M )
12
1312 A circular coil of one turn in formed by a ( 6.28 mathrm{m} ) length wire, which carries a current of 3.14 A. the magnetic field at the center of coil is :-
A ( cdot 1 times 10^{-6} T )
В. ( 4 times 10^{-6} T )
c. ( 0.5 times 10^{-6} T )
D. ( 2 times 10^{-6} T )
12
1313 Figure shows a some of the
equipotential surface of the magnetic
scalar potential. The magnetic field at a
point in the region is :
A ( cdot 2 times 10^{-5} T )
B ( cdot 10^{-5} T )
( mathbf{c} cdot 10^{-4} T )
D. ( 2 times 10^{-4} T )
12
1314 An electron revolving in an orbit of
radius ( 0.5 mathrm{A} ) in a hydrogen atom executes 10 revolutions per second. The
magnetic moment of electron due to its orbital motion will be
A ( cdot 1256 times 10^{-37} ) amp.m ( ^{2} )
B. ( 653 times 10^{-26} ) amp.m ( ^{text {2 }} )
c. zero
D. ( 256 times 10^{-26} ) amp.m ( ^{2} )
12
1315 The ratio of the magnetic field at the
centre of a circular loop to the magnetic field at the centre of the square loop, which is made by a constant length current carrying wire is:
A ( cdot frac{pi^{2}}{16} )
в. ( frac{pi^{2}}{8 sqrt{2}} )
c. ( frac{pi^{2}}{4 sqrt{2}} )
D. ( frac{pi^{2}}{2 sqrt{2}} )
12
1316 State the advantages and
disadvantages of a moving coil galvanometer. A moving coil galvanometer (M.C.G.) has
10 turns each of length ( 12 mathrm{cm} ) and
breadth ( 8 mathrm{cm} . ) The coil of M.C.G. carries a
current of ( 125 mu A ) and is kept
perpendicular to the uniform magnetic field of induction ( 10^{-2} ) T. The twist
constant of phosphor bronze fibre is ( 12 times 10^{-9} mathrm{Nm} / ) degree. Calculate the
deflection produced.
12
1317 Two coaxial solenoids of different radii
carry current I in the same direction. Let ( vec{F}_{1} ) be the magnetic force on the inner solenoid due to the outer one and ( vec{F}_{2} ) be
the magnetic force on the outer
solenoid due to the inner one. Then
( A cdot vec{F}_{1}=vec{F}_{2}=0 )
B . ( vec{F}_{1} ) is radially inwards and ( vec{F}_{2} ) is radially outwards
C ( cdot vec{F}_{1} ) is radially inwards ( vec{F}_{2}=0 )
D. ( vec{F}_{1} ) radially outwards and ( vec{F}_{2}=0 )
12
1318 If the direction of the initial velocity of the charged particle is perpendicular to the magnetic field, the orbit of charged particle will be
A. a straight line
B. a cycloid
c. a circle
D. a helix
12
1319 A single-layer coil (solenoid) has length
and cross-section radius ( R ) A number
of turns per unit length is equal to ( n ) The magnetic induction at the centre of
the coil when a current ( I ) flows through it is given as ( B=frac{x mu_{0} n I}{sqrt{1+left(frac{2 R}{l}right)^{2}}} . ) Find
( boldsymbol{x} )
12
1320 Amperes circuital law is given by
A ( cdot oint bar{H} cdot overline{d l}=mu_{0} I_{e n c} )
B . ( oint bar{B} . overline{d l}=mu_{0} I )
C ( . oint bar{B} . overline{d l}=mu_{0} J )
D ( cdot oint bar{H} cdot bar{d} l=mu_{0} J )
12
1321 A charged particle of specific charge (charge/mass) ( alpha ) is released from
origin at time ( t=0 ) with velocity ( vec{v}= )
( v_{0}(hat{i}+hat{j}) ) in a uniform magnetic field
( vec{B}=B_{0} hat{i} . ) Coordinates of the particle at
time ( t=frac{pi}{B_{0} alpha} ) are
A ( cdotleft(frac{v_{0}}{2 B_{0} alpha}, frac{sqrt{2} v_{0}}{alpha B_{0}}, frac{-v_{0}}{B_{0} alpha}right) )
В ( cdotleft(frac{-v_{0}}{2 B_{0} alpha}, 0,0right) )
( ^{mathbf{C}} cdotleft(0, frac{2 v_{0}}{B_{0} alpha}, frac{v_{0} pi}{2 B_{0} alpha}right) )
D ( cdotleft(frac{v_{0} pi}{B_{0} alpha}, 0, frac{-2 v_{0}}{B_{0} alpha}right) )
12
1322 In a long straight solenoid with cross-
sectional radius ( a ) and number of turns
per unit length, ( n ), the current varies
with the rate ( boldsymbol{I} boldsymbol{A} / boldsymbol{s} ). The magnitude of
the induced current field strength as a function of distance ( r ) from the solenoid
axis is
A ( cdot frac{1}{2} frac{n I a^{2}}{mu_{0} r} )
В ( cdot frac{1 I a^{2}}{2 mu_{0} r} )
С ( cdot frac{n I a^{2}}{mu_{0} r} )
D. ( frac{1}{2} frac{mu_{0} n I a^{2}}{r} )
12
1323 A circular current loop of magnetic moment M is in an arbitrary orientation in an external magnetic field ( bar{B} ). The work done to rotate the loop by 30 about an axis perpendicular to its plane is:
( A . M B )
в. ( sqrt{3} frac{M B}{2} )
c. ( frac{M B}{2} )
D. zero
12
1324 Write the name of fields produced by a moving charged particles. 12
1325 Two long straight parallel wires separated by a distance, carrying equal currents exert a force ( F ) per unit length on each other. If the distance of
separation is doubled, and the current in each is halved, the force per unit length, between them will be :
( A cdot F )
B. F/2
( c cdot F / 4 )
D. F/
12
1326 The distance between two thin long
straight parallel conducting wires is ( b ) On passing the same current ( i ) in them, the force per unit length between them will be
A ( cdot frac{mu_{0} i}{2 pi b} )
В. ( frac{mu_{0} i^{2}}{2 pi} )
c. ( frac{mu_{0} i^{2}}{2 pi b} )
D. zero
12
1327 A proton of mass ( m ) and charge ( q ) is
moving in a plane with kinetic energy ( boldsymbol{E} ) If there exists a uniform magnetic field
( B, ) perpendicular to the plane of the motion the portion will move in a circular path of radius
A ( cdot frac{2 E m}{q B} )
в. ( frac{sqrt{2 E m}}{q B} )
c. ( frac{sqrt{E m}}{2 q B} )
D. ( sqrt{frac{2 E q}{m B}} )
12
1328 A horizontal wire carries 200 amp
current below which another wire of
linear density ( 20 times 10^{-3} k g m^{-1} )
carrying a current is kept at ( 2 mathrm{cm} ) distance. If the wire kept below hangs in air. The current in this wire is :
A. ( 100 A )
B. ( 9.8 mathrm{A} )
( c cdot 98 A )
( D cdot 48 A )
12
1329 A pair of stationary and infinitely long bent wires is placed in the ( x ) -y plane as shown in figure. Each wire carries
current of ( 10 A . ) Segments ( L ) and ( M ) are
along the x-axis.Segments ( P ) and ( Q ) are
parallel to the y-axis such that ( O S= )
( O R=0.02 m . ) Find the magnitude and
direction of the magnetic induction at
origin ( O ) in the form of ( x times 10^{-4} ). What
is ( x )
12
1330 large metal sheet carries an electric current along its surface. Current per unit length is ( lambda . ) Magnetic field near the metal sheet is
(0)(0)(0)(0)(0)(0)(0)(0)
( A cdot frac{lambda mu}{2} )
B. ( frac{lambda mu}{2 pi} )
c. ( lambda mu_{0} )
( D cdot frac{mu}{2 pi pi} )
12
1331 ( N=2.5 times 10^{3} ) wire turns are uniformly
wound on a wooden toroidal core of very
small cross-section. A current ( I ) flows
through the wire. If the ratio ( eta ) of the magnetic induction inside the core to that at the centre of the toroid is ( x times )
( 10^{2} . ) Find ( x )
12
1332 A circular coil of radius ( R ) carries an
electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance ( r ) from the
centre of the coil, such that ( r>>R )
varies as
A. ( 1 / r )
B . ( 1 / r^{3 / 2} )
c. ( 1 / r^{2} )
D. ( 1 / r^{3} )
12
1333 An electron is projected in the same
direction of uniform magnetic field.
Then
A. the electron turns to right
B. the electron turns to left
C. the electron velocity remains constant
D. the electron velocity decreases in magnitude
12
1334 The ends of a circular coil of radius ( r )
and number of turns ( n ) is connected to
the two terminals of a cell. The
magnetic field at the centre of the coil is ( B ). If the number of turns be made ( 2 n )
keeping the radius same, the magnetic field at the centre of the coil will be:
A. ( B )
в. ( 2 B )
( c .3 B )
D. ( 4 B )
12
1335 A circular loop of radius ( 3 mathrm{cm} ) is having a current of 12.5 A. The magnitude of magnetic field at a distance of ( 4 mathrm{cm} ) on its axis is
В ( cdot 5.27 times 10^{-5} T )
( mathrm{c} cdot 6.54 times 10^{-5} T )
D. ( 9.20 times 10^{-5} T )
12
1336 A solenoid of length 1 m, area of crosssection ( 4.0 mathrm{cm}^{2} ) and having 4000 turns is placed inside another solenoid of 2000 turns having a cross-sectional ( operatorname{area} 6 mathrm{cm}^{2} ) and length 2 m. The mutual
inductance between the solenoids is
( x pi times 10^{-5} H . ) Findout the value of ( x )
12
1337 A drop of oil of mass 2 ng is kept stationary in between two plates ( 2 mathrm{cm} ) apart. A potential difference is 2 kV is applied. The number of electrons it gained is
A . 16
B. 160
( c cdot 4 )
D. 1600
12
1338 Q Type your question
the dids ul divig sultilulu dis shuwn III
fig. The ring has a narrow gap of width ( d )
in its circumference. The solenoid has
cross sectional area ( A ) and a uniform
internal field of magnitude ( B_{0} . ) Now
beginning at ( t=0, ) the solenoid current
is steadily increased so that the field
magnitude at any time ( t ) is given by
( boldsymbol{B}(boldsymbol{t})=boldsymbol{B}_{0}+boldsymbol{alpha} ) where ( boldsymbol{alpha}>0 . ) Assuming
that no change can flow across the gap,
the end of ring which has excess of positive charge and the magnitude of induced e.m.f in the ring are
respectively
A. ( X, A alpha )
В. ( X, pi R^{2} alpha )
c. ( Y, pi A^{2} alpha )
D. ( Y, pi R^{2} alpha )
12
1339 In a given region a charge particle is moving under the effect of electric and magnetic field with uniform velocity ( vec{v}=(hat{i}+hat{j}-hat{k}) mathrm{m} / mathrm{s} ) and magnetic field
is given as ( vec{B}=(2 hat{i}+hat{j}-2 k) ) T. The
electric field is given as?
( mathbf{A} cdot(i+j-k) mathrm{V} / mathrm{m} )
B. ( (i-j+k) vee / m )
c. ( (i+k) vee / m )
D. ( (-i-k) vee / ) m
12
1340 Find the mechanical work to be
performed in order to turn the frame
through ( 180^{circ} ) about its axis, with the
currents maintained constant.
A. ( 1.0 mu J )
B. ( 0.1 mu J )
c. ( 10 mu J )
D. ( 0 mu J )
12
1341 Some equipotential surfaces of the
magnetic scalar potential are shown in figure.Magnetic field at a point in the region is
A ( cdot 10^{-4} ) न
B . ( 0.5 times 10^{-4} ) T
c. ( 2 times 10^{-4} ) न
D. None of these
12
1342 Assertion
A soft iron core is used in a moving coil galvanometer to increase the strength of magnetic field.
Reason
From soft iron more number of the
magnetic lines of force passes.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect
12
1343 Which of the following statements is
true?
A. A stationary charge will experience a force in both a magnetic and electric field
B. A charge moving parallel to field lines will experience a force in both magnetic and electric fields.
C. A charge moving perpendicular to field lines will experience a force in both magnetic and electric fields.
D. It is impossible for a charge to move with constant velocity through an area that has both electric and magnetic fields
12
1344 State whether true or false:
The pattern of the magnetic field
around a conductor due to electric
current flowing through it depends on the shape of the conductor
A. True
B. False
12
1345 What will be the path of a charged
particle moving along the direction of a uniform magnetic field?
12
1346 topp
0
Fill in the blanks in the following passage(s) from the words given above.
The magnetic field produced around a straight current carrying conductor is in the form of with the
lying on the straight conductor. Take a copper wire AB. Pass it through a cardboard. Connect the wire to a battery through a key. Sprinkle some iron filings on the cardboard. Switch on the key and tap the cardboaro gently. You will find that the iron filings arrange themselves in the form of concentric circles. Reverse the direction
of current by changing the of the battery. You will find that this time too, the iron filings arrange themselves in concentric circle but in
direction. Hence, the magnetic field lines of force around a carrying electric current are concentric circles with the
conductor at the centre. The direction of
magnetic field changes if the direction of current is
12
1347 The dimension of ( 1 / 2 varepsilon_{o} E^{2}left(varepsilon_{o}right. )
permittivity of free space; E: electric field) is?
A . ( M L T^{-} )
В. ( M L^{2} T^{-2} )
c. ( M L^{-1} T^{-2} )
D. ( M L^{2} T^{-1} )
12
1348 A ( 200 M e V ) proton enters a region of the magnetic field of intensity 5 T. The
magnetic field points from south to north and the proton in moving along the vertical. The value of the force
acting on the proton will be
A. zero
В. ( 1.8 times 10^{-10} N )
c. ( 3.2 times 10^{-18} N )
D. ( 1.6 times 10^{-6} N )
12
1349 A magnet of moment ( 1.2 A m^{2} ) is kept
suspended in a magnetic field of
induction ( 2 times 10^{-6} ). The work done in
rotating it through ( 120^{circ} ) is:
A ( cdot 2.4 times 10^{-6} J )
B . ( 4.8 times 10^{-6} J )
c. ( 1.2 times 10^{-6} J )
D. ( 3.6 times 10^{-6} J )
12
1350 A tightly-wound, long solenoid carries a current of ( 2.00 A ). An electron is found to
execute a uniform circular motion
inside the solenoid with a frequency of ( 1.00 times 10^{8} ) rev ( s^{-1} ).Find the number of
turns per metre in the solenoid.
12
1351 Two particles ( X ) and ( Y ) having equal charges, after being accelerated through the same potential differences, enter in a region of uniform magnetic field and describe circular paths of radii
( R_{1} ) and ( R_{2} ) respectively. The ratio of the mass of ( X ) to that of ( Y ) is :
( ^{A} cdotleft(frac{R_{1}}{R_{2}}right)^{1 / 2} )
( ^{text {в. }}left(frac{R_{1}}{R_{2}}right)^{-1} )
( ^{c} cdotleft(frac{R_{1}}{R_{2}}right)^{2} )
D. ( left(frac{R_{1}}{R_{2}}right) )
12
1352 If magnetic field produced by a straight current carrying wire at a distance 10cm from it is X. Then the magnetic field produced at a distance ( 29 mathrm{cm} ) will be
( A cdot>x )
B.
D. all
December 27, 2019
Anjan Chatterjee
( B )
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12
1353 Two parallel straight conductors, in which current is flowing in the same direction, attract each other. The cause
of it is
A. magnetic force between the two
B. electric force between the two
c. potential difference between the two
D. mutual induction between the two
12
1354 Consider the three long,straight,parallel wires as shown in figure.Find the force experienced by a ( 25 mathrm{cm} ) length of wire ( mathrm{C} )
A ( cdot 2 times 10^{-4} N )
B. ( 3 times 10^{-4} N )
c. ( 5 times 10^{-4} N )
D. ( 6 times 10^{-4} N )
12
1355 Assertion
Force experienced by moving charge
will be maximum if direction of velocity of charge is perpendicular to applied magnetic field.
Reason
Force on moving charge is independent of direction of applied magnetic field.
A. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B. Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
C. Assertion is correct but Reason is incorrect.
D. Assertion is incorrect but Reason is correct.
12
1356 Current ( I_{o} ) flows through the solenoid of length ( L ) having ( N ) number of turns when
its connected to DC. A charged particle is projected along the axis of the solenoid
with a speed ( v_{0}, ) then the force on the
charged particle in the solenoid is:
A. Becomes zero
B. Remains same
c. Decreases
D. Increases
12
1357 A bar magnet of magnetic moment ( M ) is
divided into ‘ ( n ) ‘ equal parts by cutting
parallel to length. Then one part is suspended in a uniform magnetic field of
strength ( 2 T ) and held making an angle ( 60^{0} )
with the direction of the field. When
the magnet is released, the kinetic energy of the magnet in the equilibrium position
is:
A. ( frac{M}{n} )
B. ( M n ) J
c. ( frac{M}{n^{2}} )
D. ( M n^{2} )
12
1358 Magnetic field at point ‘O’ due to given current distribution. If 5 A current is
flowing in this system and the diameter of the loop is ( 10 mathrm{cm} )
A ( cdot 2 times 10^{-5} T, otimes )
B ( cdot 10^{-5} T, odot )
( mathbf{c} cdot 10^{-5} T, otimes )
D. ( 2 times 10^{-5} T, odot )
12
1359 Two identical loops ( P ) and ( Q ) each of
radius ( 5 mathrm{cm} ) are lying in perpendicular
planes such that they have a common centre as shown in the figure. Find the magnitude and direction of the net magnetic field at the common centre of
the two coils, if they carry currents
equal to ( 3 A ) and ( 4 A ) respectively.
12
1360 Magnetic moment of bar magnet is ( M ) The work done in turning the magnet by
( 90^{circ} ) in direction of magnetic field ( B ) will
be
A. zero
в. ( frac{1}{2} M B )
c. ( 3 M B )
D. ( M B )
12
1361 The magnetic field inside a solenoid is:
A . infinite
B. zero
c. uniform
D. non-uniform
12
1362 Complete the following statements with an appropriate word / term to be filled in the blank space(s).

Magnetic field lines emerge from the pole of a solenoid or a
permanent magnet
A. north
B. south
c. north-east
D. none of these

12
1363 While keeping area of cross-section of a solenoid same, the number of turns and length of solenoid one both doubled. The
self inductance of the coil will be?
A. Halved
B. Doubled
c. ( 1 / 4 ) times the original value
D. Unaffected
12
1364 Find an expression for the magnetic dipole moment and magnetic field induction at the centre of a Bohr’s
hypothetical hydrogen atom in the ( n^{t h} )
orbit of the electron in terms of
universal constants.
12
1365 Two moving coil meters, ( M_{1} ) and ( M_{2} )
have the following particulars:
( boldsymbol{R}_{1}=mathbf{1 0} boldsymbol{Omega}, boldsymbol{N}_{mathbf{1}}=mathbf{3 0} )
( boldsymbol{A}_{mathbf{1}}=mathbf{3 . 6} times mathbf{1 0}^{-mathbf{3}} boldsymbol{m}^{mathbf{2}}, boldsymbol{B}_{mathbf{1}}=mathbf{0 . 2 5} boldsymbol{T} )
( boldsymbol{R}_{2}=mathbf{1 4} boldsymbol{Omega}, boldsymbol{N}_{2}=boldsymbol{4} boldsymbol{2} )
( boldsymbol{A}_{2}=mathbf{1 . 8} times mathbf{1 0}^{-mathbf{3}}, boldsymbol{B}_{mathbf{2}}=mathbf{0 . 5 0} boldsymbol{T} )
(The spring constants are identical for the two meters).Determine the ratio
of (a) current sensitivity and
(b) voltage
sensitivity of ( M_{2} ) and ( M_{1} )
12
1366 Figure shows two long wires carrying
equal currents ( I_{1} ) and ( I_{2} ) flowing in
opposite directions.Which of the arrows
labeled ( A, B, C ) and ( D ) correctly
represents the direction of the
magnetic field due to the wires at a
point located at an equal distance ( d )
from each wire?
A . ( A )
B. ( B )
c. ( C )
( D . D )
12
1367 Assertion
The sensitivity of a moving coil galvanometer is increased by placing a
suitable magnetic material as a core
inside the coil.
Reason
Soft iron has a high magnetic
permeability and cannot be easily magnetized or demagnetized.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
c. Assertion is correct but Reason is incorrect
D. Assertion is incorrect but Reason is correct
12
1368 The radius of each coil of a Helmholtz
galvanometer is ( 0.1 m ) and number of
turns in each is ( 25 . ) When a current is
passed in it then the deflection of
magnetic needle observed as ( 45^{circ} . ) If the
horizontal component of earth’s magnetic field is ( 0.314 times 10^{-4} T ) then
the value of current will be
( mathbf{A} cdot 0.14 A )
B. ( 0.28 A )
c. ( 0.42 A )
D. ( 0.07 A )
12
1369 An electron is moving in a cyclotron at a speed of ( 3.2 times 10^{7} m s^{-1} ) in a magnetic
field of ( 5 times 10^{-4} ) T perpendicular to it.
What is the frequency of this electron? ( left(boldsymbol{q}=mathbf{1 . 6} times mathbf{1 0}^{-mathbf{1 9}} boldsymbol{C}, boldsymbol{m}_{boldsymbol{e}}=mathbf{9 . 1} timesright. )
( left.10^{-31} k gright) )
A ( .1 .4 times 10^{5} mathrm{Hz} )
B. ( 1.4 times 10^{7} mathrm{Hz} )
c. ( 1.4 times 10^{6} mathrm{Hz} )
D. ( 1.4 times 10^{9} mathrm{Hz} )
12
1370 A long, straight metal has a long hole of
radius a drilled parallel to the rod axis
with cross-sectional view as shown. If
the rod carries a current ( I ), the value of
the magnetic field on the axis of the rod
is:
A ( quad B=frac{mu_{0} I a^{2}}{2 pi cleft(b^{2}-a^{2}right)} )
B. ( B=frac{mu_{0} I}{2 pi c} )
c. ( quad B=frac{mu_{0} I a^{2}}{4 pi cleft(b^{2}-a^{2}right)} )
( mathbf{D} cdot B=z e r o )
12
1371 freely slide on a pair of parallel smooth
horizontal rails placed in vertical
magnetic field ( B ). The rails are
connected by a capacitor of
capacitance ( C . ) The electric resistance
of the rails and the wire is zero. If a
constant force ( F ) acts on the wire as
shown in the figure. Then, the
acceleration of the wire can be given as
( ^{mathbf{A}} cdot_{a}=frac{C^{2} B^{2} l-F}{m} )
( ^{mathbf{B}} cdot_{a}=frac{F}{m+C B l} )
( ^{mathbf{C}} cdot_{a}=frac{F C^{2} B^{2} l}{m} )
D. ( a=frac{F}{m+C B^{2} l^{2}} )
12
1372 An electron moves at right angle to a magnetic field of ( 15 times 10^{-2} T ) with a
speed of ( 6 times 10^{7} m / s . ) If the specific
charge of the electron is ( 1.7 times ) ( 10^{11} C / k g . ) The radius of the circular
path will be
( mathbf{A} cdot 2.9 mathrm{cm} )
в. ( 3.9 mathrm{cm} )
( c .2 .35 mathrm{cm} )
D. ( 2 c m )
12
1373 Electric current is passed through a straight conductor passing through the centre of a piece of cupboard. Some iron filings are sprinkled on the cardboard and tapped. How will the iron filings
spread out around the conductor?
A. settle as parallel lines
B. settle as circles
c. settle at one point
D. do not acquire any regular pattern
12

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