Electromagnetic Induction Questions

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

List of electromagnetic induction Questions

Question NoQuestionsClass
1The total charge induced in a conducting loop when it is moved in magnetic field depends on
A. The rate of change of magnetic flux
B. Initial magnetic flux only
c. The total change in magnetic flux
D. Final magnetic flux only
12
2A small circular ring is kept inside a
larger loop connected to a switch and a
battery as shown. The direction of
induced current when the switch is
made (i) ON (ii) OFF after it was ON for a
long time is:
A. clockwise, anti-clockwise
B. clockwise, clockwise
C. anti-clockwise, clockwise
D. anti-clockwise, anti-clockwise
12
3A rectangular coil of 200 turns and area
( 100 mathrm{cm}^{2} ) is kept perpendicular to a
uniform magnetic field of induction
( 0.25 T . ) If the field is reversed
in direction in 0.01 second, the average induced emf in the coil is :
A ( cdot 10^{6} V )
B . ( 10^{4} V )
( mathbf{c} cdot 10^{2} V )
D. zero
12
4A square frame with side ( a ) and a long
straight wire carrying a current ( i ) are located in the same plane as shown in figure. The frame translates to the right
with constant velocity ( v . ) Find the emf induced in the frame as a function of
distance ( boldsymbol{x} )
A ( cdot frac{mu_{0}}{7 pi} frac{2 i a^{3} v}{x(x+a)} )
В. ( frac{mu_{0}}{4 pi} frac{2 i a^{2} v}{x(x+a)} )
c. ( frac{mu_{0}}{2 pi} frac{2 i a^{4} v}{x(x+a)} )
D. ( frac{mu_{0}}{3 pi} frac{7 i a^{2} v}{x(x+a)} )
12
5A long solenoid of radius 2 cm has 100
turns/cm and is surrounded by a 100
turn coil of radius ( 4 mathrm{cm} ) having a total
resistance ( 20 Omega ). If the current changes from ( 5 A ) to ( -5 A ), find the charge through the galvanometer.
A . zero
в. ( 800 mu ) с
c. ( 400 mu ) с
D. ( 600 mu ) C
12
6Which device uses slip rings?
A. A d.c electric motor
B. A relay
C. A transformer
D. An a.c. generator
12
7Using ( varepsilon=-frac{d phi}{d t} ) and ( varepsilon=i R ) find the
current in the loop after the external
field has stopped changing.
A ( cdot frac{d i}{d t}=-left(frac{2 R}{mu_{0} pi a}right) )
в. ( frac{d i}{d t}=-frac{R}{mu_{0} a} )
c. ( frac{d i}{d t}=frac{-2 R}{mu_{0} a} i )
D. ( frac{d i}{d t}=frac{-2 R}{3 mu_{0} pi a} )
12
8A wire shaped as a circle of radius ( mathrm{R} )
rotates about the axis ( 00^{prime} ) with an
angular velocity ( omega ) as shown in figure.
Resistance of the circuit is ( R ). Find the
mean thermal power generated in the
loop during a period of a rotation.
A ( cdot frac{left(B pi a^{2} omegaright)^{2}}{4 R} )
B. ( frac{left(B pi a^{2} omegaright)^{2}}{2 R} )
( ^{mathbf{C}} cdot frac{left(3 B pi a^{2} omegaright)^{2}}{2 R} )
D. None of these
12
9A metal rod ( frac{1}{sqrt{pi}} m ) long rotates about one of its ends perpendicular to a plane whose magnetic induction is ( 4 times ) ( 10^{-3} T . ) Calculate the number of
revolutions made by the rod per second if the e.m.f induced between the ends of
the rod is ( 16 m V )
12
10Consider the time interval ( t=2.0 s ) to
( boldsymbol{t}=mathbf{4} . mathbf{0} boldsymbol{s} )
The magnetic field is perpendicular to
the plane of the loop.
12
11(d) rR
47. A circuit contains two inductors of self-inductance L, and
L2 in series (figure). If M is the mutual inductance, then
the effective inductance of the circuit shown will be
0000000
0000000
L2V
(a) L+L,
(C) L + L +M
(b) L. +L2-2M
(d) L + L + 2M
40
TI..
c
.
12
12The current passing through a choke coil of ( 5 H ) is decreasing at the rate of ( 2 A / s . ) The e.m.f. developed across the coil is
A . ( 10 V )
в. ( -10 V )
( mathrm{c} .2 .5 mathrm{V} )
D. ( -2.5 V )
12
13What is electromagnetic induction? Give an experiment which demonstrate this phenomenon.12
14In figure, if the current ( i ) decreases at a
rate ( alpha, ) then ( V_{A}-V_{B} ) is
A. zero
в. ( -alpha L )
( c cdot alpha L )
D. No relation exists
12
15Two circular coils ‘X’ and ‘Y’ are placed
closed to each other. If the current in the
coil ‘X’ is changed, will some current be induced in the coil ‘Y’? Give reason.
12
16Explain self-induction of a coil. Arrive at an expression for the induced emf in a
coil and the rate of change of current in ¡t
12
17Name four appliances wherein an electric motor, a rotating device that converts electrical energy to
mechanical energy, is used as an important component. In what respect motors are different from generators?
12
1820. A boat is moving due east in a region where the earth’s
magnetic field is 5.0 x 10-5 NA-‘m-‘ due north and
horizontal. The boat carries a vertical aerial 2 m long. If
the speed of the boat is 1.50 ms, the magnitude of the
induced emf in the wire of aerial is
(a) 1 mV
(b) 0.75 mV
(c) 0.50 mV
(d) 0.15 mV (AIEEE 2011)
12
19Describe the working of an AC generator with the help of a labelled circuit
diagram. What changes must be made in the arrangement to convert it to a DC generator?
12
20Some magnetic flux is changed from a
coil of resistance ( 10 Omega ). As a result, an
induced current is developed in it,
which varies with time as shown in the
figure. The magnitude of change in flux
through the coil in webers is:
( A )
B. 4
( c .6 )
( D )
12
21At ( t=0, ) when the magnetic field is
switched on tehe conducting rod is moved to the left at constant speed
( 5 c m / s ) by some external means. At ( t= )
( 2 s, ) net induced emf has magnitude
A . ( 0.12 V )
B. ( 0.08 V )
c. ( 0.04 V )
D. ( 0.02 V )
12
22A 100 millihenry coil carries a current of ampere. Energy stored in its magnetic field is
A . 0.5
B . 1 J
c. 0.05
D. 0.1
12
23Which of the following is not correct
A. It is a machine to accelerate charged particles or ions to high energies.
B. Cyclotron uses both electric and magnetic fields in combination to increase the energy of charged particles.
C. The operation of the cyclotron is based on the fact that the time for one revolution of an ion is independent of its speed or radius of its orbit
D. The charged particles and ions in cyclotron can move on any arbitary path
12
24Write Faraday’s laws of electro magnetic induction.12
25Consider the situation shown in figure.
The wire ( A B ) slides on the fixed rails with
a constant velocity. If the wire ( A B ) is replaced by a semicircular wire, the
magnitude of the induced current will
A. Increase
B. Remain the same
c. Decrease
D. Increase or decrease depending on whether the semicircle bulges towards the resistance or away from it.
12
26A generator with a circular coil of 100
turns of area ( 2 times 10^{-2} m^{2} ) is immersed
in a ( 0.01 T ) magnetic field and rotated at a frequency of ( 50 H z . ) The maximum emf which is produced during a cycle is
( mathbf{A} cdot 6.28 V )
B . ( 3.44 V )
( c cdot 10 V )
D. ( 1.32 V )
12
27An athlete with ( 3 mathrm{m} ) long iron rod in hand runs towards east with a speed of 30 kmph. The horizontal component of earth’s magnetic field is ( 4 times )
( 10^{-5} W b / m^{2} . ) If he runs with the rod in
horizontal and vertical positions then the induced emf generated in the rod in two cases will be
A. zero in vertical position and volt in horizonta
position.
B. 1 ( times 10 ) volt in vertical position and zero volt in in horizontal position
c. zero in both positions
D. ( 1 times 10^{-3} ) volt in both positions
12
28Two inductors ( L_{1} ) and ( L_{2} ) are connected
in parallel and a time varying current i flows as shown. The ratio of currents
( mathbf{i}_{i} / mathrm{l}_{2} ) at any time ( mathrm{t} ) is
( A cdot L_{1} / L_{2} )
B . ( L_{2} / L_{1} )
( mathbf{C} cdot frac{L_{1}^{2}}{left(L_{1}+L_{2}right)^{2}} )
( D )
12
29An AC generator is a device which
converts:
A. Electrical energy to mechanical energy.
B. Heat energy to electrical energy
c. Heat energy to light energy.
D. Mechanical energy to electrical energy
12
30The magnetic flux through a coil is ( 4 x ) ( 10^{-4} W / b / m^{2} ) at time ( t=0 . ) It reduces
to ( 10 % ) of its original value in ‘t’ seconds.If the induced e.m.f is ( 0.72 m V ) then the time ( t ) is:
( mathbf{A} cdot 0.25 s )
B. ( 0.05 s )
c. ( 0.75 s )
D. ( 1 s )
12
31If strength of magnetic field ( vec{B}=2 hat{i}+ ) ( hat{boldsymbol{j}}-hat{boldsymbol{k}} ) and area vector is ( overrightarrow{boldsymbol{A}}=mathbf{3} hat{boldsymbol{i}}-hat{boldsymbol{j}} )
then find the magnetic flux link with
area vector
A. 4 wber
B. 6 weber
c. 7 weber
D. 5 weber
12
32Magnetic flux passing through a coil is initially ( 4 times 10^{-4} ) Wh. It reduces to ( 10 % )
of its original value in ‘t’ second. If the
e.m.f. induced is ( 0.72 mathrm{mV} ) then ‘t’ in
second is:
A . 0.3
B. 0.4
c. 0.5
D. 0.6
12
33( P Q ) is an infinite current carrying
conductor. ( A B ) and ( C D ) are smooth
conducting rods on which a conductor
( E F ) moves with constant velocity ( v ) as
shown. The force needed to maintain
constant speed to ( boldsymbol{E} boldsymbol{F} ) is
( ^{mathbf{A}} cdot frac{1}{v R}left[frac{mu_{0} I v}{2 pi} ln frac{(b)}{(a)}right]^{2} )
( ^{mathrm{B}} cdot frac{v}{R}left[frac{mu_{0} I v}{2 pi} ln frac{(a)}{(b)}right]^{2} )
( ^{mathrm{c}} cdot frac{v}{R}left[frac{mu_{0} I v}{2 pi} ln frac{(b)}{(a)}right]^{2} )
D. None of these
12
34The essential difference between AC
and DC generator is:
A. AC generator has an electromagnet while DC generator has permanent magnet.
B. DC generator will generate high voltage.
C. AC generator will generate high voltage.
D. AC generator has slip rings while DC generator has a commutator
12
35The self inductance of a coil is ( 5 mathrm{m} ) H. If
a current of 2 A is flowing in it then the magnetic flux produced in the coil will be
A . 0.01 Weber
B. 10 Weber
c. zero
D. 1 Weber
12
36A solenoid of inductance ( L ) carrying a certain current is linked with a total
magnetic flux ( phi ). Now it is connected to a condenser with which it shares half of its initial energy. The total flux now linked with the solenoid is:
( A cdot frac{phi}{2} )
в. ( frac{phi}{sqrt{2}} )
( c cdot frac{phi}{2 sqrt{2}} )
D.
12
37A conducting rod of length ( boldsymbol{L}=mathbf{0 . 1 m} ) is
moving with a uniform speed ( boldsymbol{v}= )
( 0.2 m / s ) on conducting rails in a
magnetic field ( B=0.5 T ) as shown. On
one side, the end of the rails is
connected to a capacitor of capacitance ( C=20 mu F . ) Then the charges on the
capacitor plates are :
A ( cdot q_{A}=0=q_{B} )
B ( cdot q_{A}=+20 mu C ) and ( q_{B}=-20 mu C )
( mathbf{c} cdot q_{A}=+0.2 mu C ) and ( q_{B}=-0.2 mu C )
( mathbf{D} cdot q_{A}=-0.2 mu C ) and ( q_{B}=-0.2 mu C )
12
38(a) How are eddy currently generated in a conductor which is subjected to ( n ) magnetic field?
(b) Write two examples of their useful applications.
(c) How can the disadvantages of eddy currents be minimized?
12
39Epilepsy can be diagnosed using
A. ECG
B. ultrasound
c. ЕEG
D. x-ray
12
40The four wire loops shown in figure have
vertical edge lengths of either ( L, 2 L ) or
3 ( L ). They will move with the same speed
into a region of uniform magnetic field ( vec{B} ) directed out of the page. Rank them according to the maximum magnitude of the induced emf greatest to least.
A. 1 and 2 tie, then 3 and 4 tie
B. 3 and 4 tie, then 1 and 2 tie
c. 4,2,3,1
D. 4 then 2 and 3 tie, and then 1
12
41What is motional emf? State any two
factors on which it depends.
12
42An electricity generating machine consists of a turbine and a
A. Dynamo
B. core
c. Heat
D. sun
12
43A plot of magnetic flux ( (phi) ) versus current (I) is shown in the figure, for two
inductors ( A ) and ( B ). Which of the two has
the larger value of self-inductance?
12
44A non-conducting ring having charge ( q ) uniformly distributed over its circumference is placed on a rough
horizontal surface. A vertical time
varying magnetic field ( B=4 t^{2} ) is
switched on at time ( t=0 . ) Mass of the
ring is ‘m’ and radius is R. The ring starts rotating after 2 s. The coefficient of friction between the ring and the table is:
A ( cdot frac{4 q m R}{g} )
в. ( frac{2 q m R}{g} )
c. ( frac{8 q R}{m g} )
D. ( frac{q R}{2 m g} )
12
45The figure shows four wire loops, with edge lengths of either I or 21. All four
loops will move through a region of uniform magnetic field ( g ) at the same
constant velocity. In
which loop the emf induced is
maximum:
( A )
B. I
c. III
D. IV
12
46The unit of inductance is equivalent to
A. ( frac{text { volt } times text { ampere }}{text { second }} )
в. ( frac{text { ampere }}{text {volt } times text { second }} )
c. ( frac{v o l t}{text { Ampere } times text { second }} )
D. ( frac{text {volt } times text { second }}{text { ampere }} )
12
47Assertion
Induced potential across a coil and
therefore induced current is always
opposite to the direction of current due
to external source.
Reason
Lenz’s law states that induced emf
always opposes the cause due to which it is being produced.
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
48Alternating current of peak value ( left(frac{2}{pi}right) ) ampere flows through the primary coil of the transformer. The coefficient of
mutual inductance between primary and secondary coil is 1 henry. The peak
e.m.f. induced in secondary coil is (Frequency of a.c. ( =50 mathrm{Hz}) )
( A cdot 100 v )
B. 200 V
c. 300
D. 400
12
speed of ( 2 mathrm{cms}^{-1} ) on a ( mathrm{V} ) -shaped
conductor each prong of which is ( 50 mathrm{cm} ) in length immersed in a uniform
magnetic field ( mathbf{B}=mathbf{0 . 4 T}, ) perpendicular
and into the ( V ) -plane shown in the

mid-point ( C ) of the rod is at ( 0 . ) Then [both conductor and rod have resistance of 10
( ^2 ) per meter
A. the current in the circuit increases from zero to ( 300 mathrm{mA} ) during ( 20 s )
B. the current in the circuit is ( 300 mathrm{mA} ) fort ( leq 20 ) s and zero fort ( >20 ) s.
c. the current in the circuit is ( 150 mathrm{mA} ), till the rod is in contact with ( V ) -conductor
D. the current in the circuit is ( 150 mathrm{mA} ) for ( mathrm{t} leq 10 mathrm{s} ) and is ( 300 m A ) for ( 10 s<t leq 20 s )

12
50A conducting rod of length ( l ) is hinged at
point ( 0 . ) It is free to rotate in a vertical
plane. There exists a uniform magnetic field ( vec{B} ) in horizontal direction. The rod is
released from the position shown. The potential difference between the two
ends of the rod is proportional to:
This question has multiple correct options
( A cdot l^{3 / 2} )
B ( cdot l^{2} )
( c cdot sin theta )
D. ( (sin theta)^{1 / 2} )
12
51The magnetic potential energy stored in a certain inductor is ( 25 mathrm{mJ} ), when the
current in the inductor is ( 60 mathrm{mA} ). This
inductor is of inductance.
A . 1.389 н
В. 0.138 н
c. 13.89 н
D. ( 138.88 mathrm{H} )
12
52An inductor is connected to a direct
voltage source through a switch. Now
A. Very large emf is induced in inductor when switch is closed
B. Larger emf is induced when switch is opened
C. Large emf is induced whether switch is closed or opened
D. No emf is induced whether switch is closed or opened
12
53A conducting rod of length ( l ) is moving in a transverse magnetic field of strength ( B ) with velocity ( v ). The resistance of the rod is ( R ). The current in
the rod is
A ( cdot frac{B l v}{R} )
в. ( B l v )
c. ( Z e r o )
D. ( frac{B^{2} v^{2} l^{2}}{R} )
12
54A bicycle is resting on its stand in the east-west direction and the rear wheel
is rotated at an angular speed of 50 revolutions per minute. If the length of
each spoke is ( 30.0 mathrm{cm} ) and the
horizontal component of the earth’s
magnetic field is ( 4 times 10^{-5} T ), find the
emf induced between the axis and the
outer end of a spoke. Neglect centripetal
force acting on the free electrons of the spoke.
12
55Three identical wires are bent into
semi-circular arcs each of radius ( boldsymbol{R} )
These arcs are connected with each
other to form a closed mesh such that
one of them lies in x-y plane, one in ( y-z ) plane and the other in z-x plane as
shown in figure. In the region of space, a uniform ( vec{B}=B_{0}(hat{i}+hat{j}) ) exists, whose magnitude increases at a constant rate
( boldsymbol{d} boldsymbol{B} / boldsymbol{d} boldsymbol{t}=boldsymbol{alpha} . ) Calculate the magnitude of
emf induced in the mesh and mark
direction of flow of induced current in
the mesh.
12
56When the current in a coil changes from 2 amp. to 4 amp. in 0.05 sec., an e.m.f. of 8 volt induced in the coil. The coefficient
of self inductance of the coil is
A. 0.1 henry
B. 0.2 henry
c. 0.4 henry
D. 0.8 henry
12
57In a ( D C ) generator, the induced e.m.f, in
the armature is
A ( . D C )
в. ( A C )
c. Fluctuating ( D C )
D. Both ( A C ) and ( D C )
12
58Current in a coil of self-inductance
( 2.0 H ) is increasing as ( i=2 sin t^{2} . ) The
amount of energy spent during the period when the current changes from 0
to ( 2 A ) is:
A . 15
в. 2 J
( c .3 J )
D. ( 4 J )
12
59Name and state the principle of a simple a.c. generator. What is its use?12
60A solenoid ( 30 c m ) long is made by
winding 2000 loops of wire on an iron
rod whose cross-section is ( 1.5 mathrm{cm}^{2} ). If
the relative permeability of the iron is ( 6000, ) what is the self-inductance of the
solenoid?
( mathbf{A} cdot 15 H )
в. ( 2.5 H )
( c .3 .5 H )
D. ( 0.5 H )
12
61What experiment do you suggest to understand Faradays law?What items are required? What suggestions do you give to get good results of the experiment? Give precautions also.12
62A charged particle oscillates about its equilibrium position with an frequency of ( 100 M H z . ) What is the frequency of
electromagnetic waves produced by the oscillator?
12
63Some magnetic flux is changed in a coil
of resistance 10 ohm. As a result an
induced current is developed in it,
which varies with time as shown in
figure. The magnitude of change in flux
through the coil in Webers is (Neglect
self inductance of the coil)
( A cdot 2 )
( B .4 )
( c cdot 6 )
( D )
12
64Explain ‘Electric generator’ with the help of the following points :
i. Principle of an electric generator.
ii. Function of slip rings.
iii. Any two uses of a generator.
12
65A rod AB moves with a uniform velocity
( v ) in a uniform magnetic field as shown in figure.
( begin{array}{llllll}mathbf{X} & mathbf{X} & mathbf{X} & mathbf{A} & mathbf{X} & mathbf{X} & mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} & mathbf{n} & mathbf{X} & mathbf{X} & mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} & mathbf{n} & mathbf{X} & mathbf{X} & mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} & mathbf{B} & mathbf{X} & mathbf{X} & mathbf{X}end{array} )
A. The rod becomes electrically charged
B. The end A becomes positively charged
c. The end B become positively charged
12
66Electromagnetic induction is the:
A. charging of a body with a positive charge
B. production of current by relative motion between a magnet and a coil
C. rotation of the coil of an electric motor
D. generation of magnetic field due to a current carrying solenoid
12
67The coefficients of self induction of two
coils are ( L_{1}=8 mathrm{mH} ) and ( L_{2}=2 mathrm{mH} )
respectively. The current rises in the two
coils at the same rate. The power given
to the two coils at any instant is same. The ratio of energies stored in the coils
will be:
A. ( frac{W_{1}}{W_{2}}=4 )
B. ( frac{W_{1}}{W_{2}}=frac{1}{4} )
( mathbf{c} cdot frac{W_{1}}{W_{2}}=frac{3}{4} )
D. ( frac{W_{1}}{W_{2}}=frac{4}{3} )
12
68Match column I with column II and
select the correct option from the codes
given below
12
69A ( 200 k m ) long telegraph wire has a capacitance of ( 0.014 mu F / k m . ) If it carries an ac of ( 5 k H z, ) what should be the inductance required to be connected in series, so that the impedance is minimum? Take ( pi=sqrt{10} )12
70Constant magnetic field in the coil induces
A . high
B. low
( c cdot n o )
D. alternating
12
71State Faraday’s laws of electromagnetic induction and Lenz’s law.12
72at opposite sides of an infinitely long straight conducting wire as shown in the figure. If current in the wire is slowly
decreased, then the direction of the
nduced current will be :
A. clockwise in ( A ) and anticlockwise in ( B )
3. anticlockwise in ( A ) and clockwise in ( B )
c. clockwise in both ( A ) and ( B )
D. anticlockwise in both ( A ) and ( B )
12
73The Sl unit of inductance is12
74A circular coil of conducting wire has an area ( A ) and number of turns ( N . ) It is lying in a vertical plane in a region where uniform magnetic field B exist with field direction normal to the coil plane. If the coil is rotated about a vertical axis
by an angle ( pi ) in 0.5 seconds, then the value of the emf induced at the ends of
the coil is
( A ). 4 NAB
B. ( 4 pi ) NAB
c. 8 NAB
D. 8 ( pi ) NAB
12
75A flat circular coil of ( n ) turns, area ( A ) and resistance ( boldsymbol{R} ) is placed in a uniform
magnetic field ( B ). The plane of coil is
initially perpendicular to ( B ). When the
coil is rotated through an angle of ( 180^{circ} )
about one of its diameter, a charge ( Q_{1} )
flows through the coil. When the same
coil after being brought to its initial position, is rotated through an angle of
( 360^{circ} ) about the same axis a charge ( Q_{2} )
flows through it. Then ( Q_{2} / Q_{1} )
A . 1
B . 2
c. ( 1 / 2 )
D.
12
7615. A short-circuited coil is placed in a time-varying magnetic
field. Electrical power is dissipated due to the current
induced in the coil. If the number of turns were to be
dissipated would be
(a) halved
(b) the same
(c) doubled
12
77Find the current through the conductor
during its motion
12
78A conducting rod ( P Q ) of length ( L= )
1.0 ( m ) is moving with a uniform speed
( boldsymbol{v}=20 boldsymbol{m} / boldsymbol{s} ) in a uniform magnetic field
( B=4.0 T ) directed into the paper ( A )
capacitor of capacity ( boldsymbol{C}=mathbf{1 0} boldsymbol{mu} boldsymbol{F} ) is
connected as shown in figure. Then
( mathbf{A} cdot q_{A}=+800 mu C ) and ( q_{B}=-800 mu C )
B ( cdot q_{A}=-800 mu C ) and ( q_{B}=+800 mu C )
( mathbf{c} cdot q_{A}=0=q_{B} )
D. charged stored in the capacitor increases exponentially with time
12
79In an inductance coil the current
increases from zero to ( 6 A ) in 0.3 second
by which an induced e.m.f. of ( 60 mathrm{V} ) is produced in it. The value of coefficient of self-induction of coil is :
A. ( 1 H )
в. ( 0.5 H )
( c .2 H )
D. ( 3 H )
12
80are connected on the top by a capacitor
C. A sliding conductor AB of length L
slides with its ends in contact with the
bars. The arrangement is placed in a uniform horizontal magnetic field
directed normal to the plane of the
figure. The conductor is released from
rest. The displacement ( (x) ) in meter of
the conductor at time ( t=2 ) sec is:
( left(text { Given } boldsymbol{m}=mathbf{1 0 0} boldsymbol{g} boldsymbol{m}, boldsymbol{g}=mathbf{1 0 m} / boldsymbol{s}^{2}, boldsymbol{B}=right. )
100Tesla, ( boldsymbol{L}=mathbf{1} boldsymbol{m}, boldsymbol{a} boldsymbol{n} boldsymbol{d} boldsymbol{C}=mathbf{1 0} boldsymbol{mu} boldsymbol{F}) )
A . 10
B. 14
( c cdot 7 )
( D )
12
818
the magnetic field changes at the rate
of ( d B / d t . A B=B C . ) Calculate the
induced emf between the ends of length
( A B, ) if ( A C ) and ( B C ) were removed from
the circuit.
( ^{mathbf{A}} cdot R^{2}left(frac{d B}{d t}right) )
( ^{mathbf{B}} cdot 4 R^{2}left(frac{d B}{d t}right) )
( ^{mathbf{C}} cdot frac{1}{2} R^{2}left(frac{d B}{d t}right) )
( ^{mathrm{D}} 2 R^{2}left(frac{d B}{d t}right) )
E. None of the above
12
induction.
12
83Flux density under trailing pole tips in
case of generator will :
A. increase
B. decrease
c. either increase or decrease
D. none of the above
12
84Define electromagnetic induction?12
85A long wire carrying current ( i ) is placed
close to a U-shaped conductor (of negligible resistance). A wire of length ( l )
as shown in figure slides with a velocity
v. Find the current induced in the loop
as a function of distance ( x ) from the
current carrying wire to slider.
A ( cdot frac{mu_{0} i l u}{R x} )
в. ( frac{mu_{0} i l u}{2 pi R x} )
c. ( frac{mu_{0} i l u}{2 R x} )
D. ( frac{mu_{0} i l u}{4 pi R x} )
12
86The magnitude of induced current in a closed coil increases with the increase
in the ( ldots ldots . . . . . . . . . . ) of magnetic lines of force.
A. strength
B. alternating
c. magnetic field
D. less
12
87To convert mechanical energy into
electrical energy, one can use This question has multiple correct options
A. ( D C ) dynamo
B. ( A C ) dynomo
c. motor
D. transformer
12
88The mutual inductance between two
coils when a current of 5 A changes to ( 10 mathrm{A} ) in ( 1 mathrm{s} ) and induces an emf of ( 100 mathrm{m} )
Vin the secondary is
A . ( 20 mathrm{m} ) н
B. ( 10 mathrm{mH} )
c. ( 30 mathrm{mH} )
D. ( 15 mathrm{mH} )
12
89A rod of length ( L ) rotates in the form of a
conical pendulum with an angular velocity ( omega ) about its axis as shown in
figure. The rod makes an angle ( boldsymbol{theta} ) with the axis. The magnitude of the motional emf developed across the two ends of
the rod is
( A )
в.
( ^{mathrm{c}} cdot frac{1}{2}^{B omega L^{2} cos ^{2} theta} )
D.
12
90An inductor is connected to a battery through a switch. The emf induced in the inductor is much larger when the switch is opened as compared to the emf induced when the switch is closed.
Is this statement true or false?
12
91Collect information of experiments done by Faraday.12
92– 17. A long solenoid having 200 turns per centimeter carries
a current of 1.5 A. At the center of the solenoid is placed
a coil of 100 turns of cross-sectional area 3.14 x 10-4 m²
having its axis parallel to the field produced by the
solenoid. When the
12
93Study involving both electricity and magnetism is called
A. electromagnetism
B. magnetoelectricism
c. electricmagnetism
D. magneticelectromerism
12
94Two coils ( P ) and ( Q ) are kept near each other. When no current flows through coil ( P ) and current increases in coil ( Q ) at
the rate ( 10 A / s ), the e.m.f. in coil ( P ) is
( 15 m V . ) When coil ( Q ) carries no current
and current of ( 1.8 A ) flows through coil
( P, ) the magnetic flux linked with the coil
( Q ) is
A. ( 1.4 mathrm{m} mathrm{Wb} )
B . ( 2.2 mathrm{m} mathrm{Wb} )
( mathbf{c} .2 .7 mathrm{m} mathrm{Wb} )
D. ( 2.9 mathrm{m} mathrm{Wb} )
12
95Pick out the wrong statement.
A. Gauss’s law of magnetism is given by ( alpha phi B . d s=0 )
B. An EM wave is a wave radiated by a charge at rest and propagates through electric field only
C. A time varying electric field is a source of changing magnetic field
D. Faraday’s law of EM induction is ( phi E . d I=-frac{d phi_{B}}{d t} )
12
96In what direction does the induced
current in coil flow
( A cdot A ) to ( B )
B. в to A
c. No current
D. cant say
12
97A coil of resistance ( 400 Omega ) is placed in a magnetic field. If the magnetic flux ( phi(W b) ) linked with the coil varies with time ( t(sec ) ) as ( Phi=50 t^{2}+4 )
The current in the coil at ( t=2 sec ) is
A. 2A
B. 1A
( c .0 .5 A )
D. 0.1A
12
98D 211
x
x
9. A wire is bent to form the double loop shown in
figure. There is a uniform magnetic field directed into the
plane of the loop. If the magnitude xa X X X bx
of this field is decreasing, the cur-
rent will flow from
(a) a to b and c to do
x x
(b) b to a and d to c
(c) a to b and d to c art
х Хd x
(d) b to a and c to d
x
x
x
x
12
99An ac generator produced an output voltage ( boldsymbol{E}=mathbf{1 7 0} sin mathbf{3 7 7 t} ) volts, where ( t )
is in seconds. The frequency of ac voltage is
( mathbf{A} cdot 50 H z )
в. ( 110 H z )
( mathbf{c} cdot 60 H z )
D. ( 230 H z )
12
100The value of mutual inductance can be
increased by
A. decreasing N
B. increasing
c. winding the coil on wooden frame
D. winding the coil on china clay
12
101x
x
x
x
6. A thin semicircular conducting ring of radius R is falling
with its plane vertical in a
horizontal magnetic induction B
B. At the position MNQ, the
speed of the ring is v and the
potential difference developed
across the ring is
(a) zero
(b) ByteR-/2 and Mis at higher
potential
(c) TRBv and Q is at higher potential
(d) 2RBV and Q is at higher potential
(d) Poto of de
M
12
102Direction of induced EMF can be found
from
A. Lenz law
B. Laplace law
c. Fleming law
D. None of the above
12
103The coil ( X ) and ( Y ) have the same number
of turns and length. Each has a flux
density ( B ) in the middle and a flux
density ( 0.5 B ) at the ends when carrying the same current. When the coils are
joined to form a long coil of twice the
length of ( X ) or ( Y ) and the current ( I ) is sent through the coil, the flux density in the middle is given by:
A. 0
в. ( 0.5 B )
c. ( 2 B )
D. ( B )
12
104The current flowing through resistance
( R ) if the rod ( M N ) moves toward left and
the rod ( M^{prime} N^{prime} ) moves toward the right is
( A )
[
frac{B l v}{R+(r / 2)}
]
в. ( frac{2 B l v}{R+r} )
c. zero
( D )
[
frac{3 B l v}{2(R+r)}
]
12
105A conducting wire of length ( ell ) and mass
( m ) can slide without friction on two
parallel rails and is connected to
capacitance ( C . ) Whole system lies in a
magnetic field ( B ) and a constant force
( F ) is applied to the rod. Then
This question has multiple correct options
A. the rod moves with constant velocity
B. the rod moves with an acceleration of ( frac{F}{m+B^{2} ell^{2} c} )
c. there is constant charge on the capacitor
D. charge on the capacitor increases with time
12
106A coil of insulated Copper wire is connected to a Galvanometer.
What happens, if a bar magnet is:
(i) pushed into the coil?
(ii) withdrawn from inside the coil?
(iii) held stationary inside the coil?
12
107Assertion: When two coils are wound on
each other, the mutual induction
between the coils is maximum.
Reason: Mutual induction does not
depend on the orientation of the coils.
A. Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
c. Assertion is true but Reason is false
D. Assertion is false but Reason is true
12
108Whenever there is a change in the
magnetic flux linked with a closed
circuit, an emf and a current are
induced in the circuit. This statement is
referred to as:
A. Lenz’s law
B. Faraday’s second law of electromagnetic induction
C. Faraday’s first law of electromagnetic induction
D. Laplace’s law
12
109What is the self inductance of a coil in
which an induced emf of ( 2 V ) is set up,
when the current is changing at the rate
of ( 4 A s^{-1} )
A . ( 0.5 mathrm{mH} )
в. ( 0.05 mathrm{H} )
( c cdot 2 H )
D. ( 0.5 H )
12
110The out put of a dynamo using a split ring commutator is
A . dc
B. ac
c. fluctuating dc
D. half wave rectified da
12
111Figure shows a point ( mathrm{P} ) near a long
conductor XY carrying a current 1. MN is a short current carrying conductor, kept at the point ( P, ) parallel to the conductor
( mathbf{X Y} )
(i) What is the direction of magnetic
flux density ‘B’ at the point P due to the current flowing through XY?
(ii) What is the direction of the force
experienced by the conductor MN due to the current flowing through XY?
12
112A conducting disc of radius r rotates with a small constant angular velocity ( omega ) about its axis. A uniform magnetic
field B exists parallel to the axis of rotations. Find the motional emf
between the center and the periphery of
the disc.
12
113Two coils have a mutual inductance
( 0.55 H . ) The current changes in the first
coil according to equation ( boldsymbol{I}=boldsymbol{I}_{0} sin omega boldsymbol{t} )
where, ( I_{0}=10 A ) and ( omega=100 pi r a d / s )
The maximum value of emf in the
second coil is
A . ( 2 pi )
в. ( 5 pi )
c. ( pi )
D. ( 4 pi )
12
114What are Eddy currents? Describe the ways in which they are used to
12
115In alternative current generator, ( A C )
current reverses its direction:
A. 20 times per second
B. 50 times per second
c. once per second
D. twice per second
12
116Lenz’s law is a consequence of the law of conservation of
A. charge
B. mass
c. energy
D. momentum
12
117A metallic rod of ( ^{prime} boldsymbol{L}^{prime} ) length is rotated
with angular frequency of ( ^{prime} omega^{prime} ) with one
end hinged at the centre and the other
end at the circumference of a circular
passing through the centre and perpendicular to the plane of the ring. ( mathbf{A} )
constant and uniform magnetic field ( boldsymbol{B} ) parallel to the axis is present
everywhere. Deduce the expression for
the emf between the centre and the
metallic ring.
(a)
( (b) )
12
118A conducting disc of radius R is rotating with angular velocity ( omega . ) Mass of electron is and charged e. If electrons are the
current carries in a conductor, the
potential difference between the center and the edge of the disc is:
( ^{A} cdot frac{m omega^{2} R^{2}}{e} )
B. ( frac{m omega^{2} R^{2}}{4 e} )
c. ( frac{m omega^{2} R^{2}}{3 e} )
D. ( frac{m omega^{2} R^{2}}{2 e} )
12
119In electromagnetic induction, the induced charge in a coil is independent
of
A . Time
B. Change in flux
c. Resistance in the circuit
D. None of the above
12
120In the process of electromagnetic induction, the magnitude of the induced emf does not depend on
A. The number of turns of the coil
B. The magnetic flux linked with the coil
c. The rate of change of magnetic flux linked with the coil
D. Area of the coil
12
121Assertion
In the phenomenon of mutual induction,
self Induction of each of the coil
persists.
Reason
Self induction arises when strength of
current in one coil changes. In mutual induction, current is changing in both
the individual coils.
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
122A circular coil of mean radius of ( 7 mathrm{cm} )
and having 4000 turns is rotated at the rate of 1800 revolutions per minute in
the earth’s magnetic field ( (mathrm{B}=mathbf{0 . 5} ) gauss), the peak value of emf induced in coil will be?
A . ( 1.158 mathrm{v} )
B. ( 0.58 mathrm{V} )
c. ( 0.29 v )
D. ( 5.8 v )
12
123A square wire frame of side ( a ) is placed
a distance ( b ) away from a long straight
conductor carrying current ( I ). The frame
has resistance ( R ) and self inductance ( L )
The frame is rotated by ( 180^{circ} ) about ( 00^{prime} )
as shown in figure. Find the electric charge flown through the frame.
( ^{A} cdot frac{2 mu_{0} i a^{2}}{2 pi R b} )
В. ( frac{mu_{0} i}{2 pi R} log _{e} frac{b+a}{b-a} )
c. ( frac{mu_{0} i a}{2 pi R} log _{e} frac{b+a}{b-a} )
D. none of thes
12
124The magnetic field is varying as ( boldsymbol{B}(boldsymbol{t})= )
( B_{o} t ) in the circuit as shown in the figure
Then the emf induced in the circuit will
be
( mathbf{A} cdot 2 pi a^{2} B_{0} )
В . ( pi a^{2} B_{0} )
c. ( frac{a^{2} B_{0}}{2} )
D. ( frac{pi a^{2} B_{0}}{2} )
12
125Suppose the loop in Exercise is stationary but the current feeding the electromagnet that produces the magnetic field is gradually reduced so that the field decreases from its initia
value of ( 0.3 mathrm{T} ) at the rate of ( 0.02 mathrm{T} s^{-1} . ) If
the cut is joined and the loop has a resistance of 1.6 ohm , how much power is dissipated by the loop as heat? What is the source of this power?
Exercise :
I A rectangular wire loop of sides ( 8 mathrm{cm} ) and ( 2 mathrm{cm} ) with a small cut is moving out of a region of uniform magnetic field of magnitude ( 0.3 mathrm{T} ) directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is ( 1 mathrm{cm} )
( s^{-1} ) in a direction normal to the (a)
longer side,
(b) shorter side of the loop?
For how long does the induced voltage last in each case?
12
126(a) ZM
46. A small coil of radius r is placed at the center of a large
coil of radius R, where R>>r. The two coils are coplanar.
The mutual inductance between the coils is proportional to
(a) r/R
(b) r/R
(c) r-/R2
(d) r/R
12
127A dynamo does not consist of
A. a bar magnet
B. two carbon brushes
c. the external circuit
D. all of these
12
128When an electric cell drives current
through load resistance, its back emf,
A. Supports the original emf
B. opposes the original emf
c. supports if internal resistance is low
D. Opposes if load resistance is large
12
129Whenever current is changed in a coil an induced e.m.f. is produced in the same coil, This property of the coil is due to
A. mutual induction
B. self induction
c. eddy currents
D. hysteresis
12
130Two identical conductors ( P ) and ( Q ) are
placed on two frictionless rails ( R ) and ( S )
in a uniform magnetic field directed
into the plane. If ( P ) is moved in the
direction shown in figure with a
constant speed, then rod ( Q )
begin{tabular}{c|c|c}
& ( P ) & ( Q ) \
& & \
( times ) & ( times ) & ( times ) \
hline( times ) & ( widehat{V} ) & ( times ) & ( times ) \
hline( s ) & & & \
hline( times ) & ( times ) & ( times ) \
hline
end{tabular}
A. will be attracted toward ( P )
B. will be repelled away from ( P )
c. will remain stationary
D. may be repelled away or attracted toward ( P )
12
131The two rails of a railway track,
insulated from each other and the
ground, are connected to millivoltmeter. What is the reading of the
millivoltmeter when a train passes at a
speed of ( 180 mathrm{km} / mathrm{hr} ) along the track,
given that the vertical component of
earth’s magnetic field is ( 0.2 times )
( 10^{-4} w b / m^{2} ) and rails are separated by 1
metre
A ( cdot 10^{-1} ) volt
B. ( 10 mathrm{mV} )
c. 1 volt
( mathbf{D} cdot 1 m V )
12
132A solid metal cube of edge length ( 2 mathrm{cm} )
is moving in a positive ( y ) direction at a constant speed of ( 6 m / s . ) There is a
uniform magnetic field of ( 0.1 T ) in the
positive ( z- ) direction. The potential
difference between the two faces of the
cube perpendicular to the ( x- ) axis, is:
( mathbf{A} cdot 6 m V )
B. ( 1 mathrm{mV} )
c. ( 12 mathrm{mV} )
D. ( 2 m V )
12
133The coil is rotated in a clockwise
direction in the magnetic field at a
constant rate to induce a current in the
wire. If the direction of rotation of the
coil is reversed and coil remains
rotating at the same constant rate, Identify the correct statement.
A. The current in the coil will reverse its direction
B. The current in the coil will stop flowing
c. The current in the coil will continue to flow in the same direction as before
D. The current in the coil will decrease steadily
E. The current in the coil will increase steadily
12
134A long solenoid with 10 turns per ( mathrm{cm} )
has a small loop of area ( 3 mathrm{Cm}^{2} ) placed inside, normal to the axis of the solenoid. If the current carried by the
solenoid changes steadily form ( 2 A ) to ( 4 A ) in ( 0.2 s, ) what is the induced voltage
in the loop, while the currect is changing?
A ( cdot 4.2 times 10^{-8} )
B. ( 2.8 times 10^{-8} )
C ( .7 .3 times 10^{-6} )
D. ( 3.8 times 10^{-6} )
12
135Whenever the magnetic flux linked with a coil changes, an induced e.m.f. is produced in the circuit. The e.m.f. lasts
A. for a short time
B. for a long time
c. for ever
D. so long as the change in flux takes place
12
136Whenever the magnetic flux linked with a coil changes, then there is an induced emf in the circuit. This emf lasts:
A. for a short time
B. for a long time
( c . ) for ever
D. so long as the change in the flux takes place
12
137There are two thin wire rings, each of radius R, whose axes coincide. The charges on the rings are ( mathrm{q} ) and q.Evaluate the potential difference between the centers of the rings separates by a distance a.
A ( cdot frac{q}{pi varepsilon_{0}}left[frac{1}{R}+frac{1}{sqrt{R^{2}+a^{2}}}right] )
B ( cdot frac{q}{2 pi varepsilon}left[frac{1}{R}+frac{1}{sqrt{R^{2}+a^{2}}}right] )
c. ( frac{q}{2 pi varepsilon_{0}}left[frac{1}{R}-frac{1}{sqrt{R^{2}+a^{2}}}right] )
D. ( frac{2 q}{pi varepsilon_{0}}left[frac{1}{R}-frac{1}{sqrt{R^{2}+a^{2}}}right] )
12
138Two coils of self inductances ( 2 mathrm{mH} ) and
( 8 mathrm{mH} ) are placed so close together that the effective flux in one coil is
completely linked with the other. The mutual inductance between these coils is:
( A cdot 10 mathrm{mH} )
B. ( 6 mathrm{mH} )
( c cdot 4 m H )
D. 16 mH
12
139A rectangular coil ( A B C D ) is rotated
anticlockwise with a uniform angular velocity about the axis shown in figure.
The axis of rotation of the coil as well as
the magnetic field ( B ) is horizontal. The
induced emf in the coil would be
minimum when the plane of the coil
A. is horizontal
B. makes and angle ( 45^{circ} ) with direction of magnetic field
( mathrm{c} ). is at right angle to the magnetic field
D. makes and angle of ( 30^{circ} ) with the magnetic field
12
1405. A and B are two metallic rings placed at opposite sides of
an infinitely long straight conducting wire
as shown in figure. If current in the wire
is slowly decreased, the direction of the
induced current will be
(a) clockwise in A and anticlockwise in B
(b) anticlockwise in A and clockwise in B
(c) clockwise in both A and B
(d) anticlockwise in both A and B
12
141Will the current be time dependent?12
142The flux linked with a coil of any instant
( t ) is given by ( phi=t^{2}-5 t+25 . ) The
induced emf ( operatorname{at} t=4 s ) is?
A ( .2 v )
B. ( -3 v )
c. ( 4 v )
D. – ( 4 v )
12
143A rod lies across frictionless rails in
uniform magnetic field ( vec{B} ) as shown in Fig. The rod moves to the right with
speed ( V . ) In order to make the induced
emf in the circuit to be zero, the
magnitude of the magnetic field should.
begin{tabular}{|l|l|}
hline & \
hline(8) & 8 \
hline & ( bigotimes ) \
hline \
hline
end{tabular}
12
144If the coil in a simple generator is wound around a soft iron core then:
A. strength of magnetic field increases.
B. current produced will be increased.
c. voltage produced will be increased.
D. all
12
145a. Redraw the diagram!
b. This diagram represents
c. Label the parts of the diagram.
d. Mention the principle used in the device denoted by this diagram
12
146The dimensions of self- induction are :
( mathbf{A} cdotleft[M L T^{-2}right] )
B . ( left[M L^{2} T^{-1} A^{-2}right. )
( mathbf{c} cdotleft[M L^{2} T^{-2} A^{-2}right. )
D・ ( left[M L^{2} T^{-2} A^{2}right] )
12
placed near a long straight current-
carrying wire. The dimensions are
shown in the figure. The lone wire lies in
the plane of the loop. The current in the
long wire varies as ( boldsymbol{I}=boldsymbol{I}_{mathbf{0}}(boldsymbol{t}) . ) The
mutual inductance of the pair is
A ( cdot frac{mu_{0} a}{2 pi} ln left(frac{2 a+l}{l}right) )
B. ( frac{mu_{0} a}{2 pi} ln left(frac{2 a-l}{l}right) )
c. ( frac{2 mu_{0} a}{2 pi} ln left(frac{a+l}{l}right) )
D. ( frac{mu_{0} a}{2 pi} ln left(frac{a+l}{l}right) )
12
148The two rails of a railways track, insulated from each other and the
ground, are connected to a milli voltmeter. What is the reading of the milli voltmeter when a train travels at a
speed of ( 20 mathrm{ms}^{-1} ) along the track, given that the vertical component of the
earth’s magnetic field is ( 0.2 times 10^{-4} ) ( mathrm{Wbm}^{-2} ) and the rails are separated by 1
( mathrm{m} ? )
A. 4 mv
B. ( 0.4 mathrm{mv} )
c. ( 80 mathrm{mv} )
D. 10 mv
12
149Magnetic flux through a circuit of
resistance ( 20 Omega ) is changed from 20 Wb to ( 40 mathrm{Wb} ) in ( 5 mathrm{ms} ). Charge passed through the circuit during this time is
A . ( 1 mathrm{c} )
B. 2
c. zero
D. ( 0.5 mathrm{c} )
12
150The magnetic flux through a circular
carrying a current of ( 2.0 A ) is 0.8 weber.
If the current reduces to ( 1.5 A ) in ( 0.1 s )
the induced emf be
A . ( 2.0 V )
в. ( 4.0 V )
( c .8 .0 V )
D. None of the above
12
151toppr
uniform speed ( 20 mathrm{m} / mathrm{sec} . ) Size of
magnet is ( 2 times 1 times 2 mathrm{cm} ) and size of coil
( 4 times 6 mathrm{cm} ) as shown in figure. The correct
variation of induced emf with time is :
(Assume at ( t=0, ) the coil enters in the
magnetic field)
4
3
( c )
( D )
12
152topp
the same wire as shown in figure.
( A E F D ) is a square of side ( 1 m ) and
( boldsymbol{E B}=boldsymbol{F C}=mathbf{0 . 5 m .} ) The entire circuit is
placed in a steadily increasing, uniform magnetic field directed into the plane of paper and normal to it. The rate of
change of the magnetic field is ( 1 T s^{-1} )
The resistance per unit length of the
wire is ( 1 Omega m^{-1} ). Find the magnitude ano
direction of the current in the segment ( A E, B E ) and ( E F )
( ^{mathbf{A}} cdot frac{6}{22} A, E ) to ( A ; frac{7}{22} A, B ) to ( E ; frac{1}{22} A, F ) to ( E )
B. ( frac{1}{22} A, ) E to ( A ; frac{6}{22} A, E ) to ( B ; frac{7}{22} A, F ) to ( E )
c. ( frac{7}{22} A, ) E to ( A ; frac{6}{22} A, B ) to ( E ; frac{1}{22} A, F ) to ( E )
12
153A wire in the shape of an equilateral
triangle with sides of length ( 1.00 m ) is
kept in a magnetic field of ( 2.00 T )
pointing to the right. Find out the magnitude of the magnetic flux passing through the triangle?
A. ( 0 W b )
в. ( 1.00 mathrm{Wb} )
c. ( 1.73 W b )
D. 2.00Wb
E. ( 3.46 W b )
12
154Choose the correct options
This question has multiple correct options
A. Sl unit of magnetic flux is henry-ampere
B. SI unit of coefficient of self-inductance is ( J / A )
C. Sl unit of coefficient of self inductance is
( frac{v o l t-s e c o n d}{a m p e r e} )
D. Sl unit of magnetic induction is weber
12
155Two similar circular loops carry equal
currents in the same direction. On
moving the coils further apart, the
electric current will
A. increase in both
B. decrease in both
C. remain unaltered
D. increases in one and decreases in the second
12
156Give one example in which 10 V may be
fatal
This question has multiple correct options
A. when touched to tongue
B. when touched with wet hand
C. when touched with unaided hand
D. when it is a storage battery
12
157Self inductance of long solenoid is directly proportional to- ( (A ) is area of cross section)
A. ( A )
B . ( A^{2} )
c. ( A^{3} )
D. ( A^{4} )
12
158Light with energy flux of 18 w ( / mathrm{cm}^{2} ) falls
on a non reflecting surface of area 20
( mathrm{cm}^{2} ) at normal incidence the
momentum delivered in 30 minutes ise
A ( cdot 1.2 times 10^{-6} mathrm{kgms}^{-1} )
B . ( 2.16 times 10^{-3} mathrm{kgms}^{-1} )
C. ( 1.8 times 10^{-3} mathrm{kgms}^{-1} )
D. ( 3.2 times 10^{-3} mathrm{kgms}^{-1} )
12
159A conducting circular loop is placed in a uniform magnetic field ( mathrm{B}=0.025 mathrm{T} ) with its plane perpendicular to the magnetic field. The radius of the loop starts
shrinking at ( 1 mathrm{mm} mathrm{s}^{-1} ). The induced emf
in the loop when the radius is ( 2 mathrm{cm} ) is:
A. ( 2 pi mu V )
в. ( pi mu V )
c. ( frac{pi}{2} mu V )
D. ( 3.2 pi mu V )
12
160A square loop of side ( 10 mathrm{cm} ) and resistance ( 0.5 Omega ) is placed vertically in the east-west plane. A uniform
magnetic field of ( 0.10 mathrm{T} ) is set up across the plane in the north-east direction. The magnetic field is decreased to zero
in 0.70 s at a steady rate. The magnitudes of induced emf and current during this time-interval is then
( A cdot 1 mathrm{mV}, 2 mathrm{mA} )
B. ( 1 mathrm{mV}, 1 mathrm{ma} )
c. ( 2 mathrm{mv}, 2 mathrm{mA} )
D. ( 2 mathrm{mV}, 1 mathrm{mA} )
12
161Flux ( phi( ) in webers) in a closed circuit of resistance 10 ohm varies with time ( t ) (in
seconds according to the equation ( phi=6 t^{2}-5 t+1 . ) What is the
magnitude of the induced current in 0.25 second :
A. ( 0.8 mathrm{A} )
B. 1.2 A
c. 0.6 A
D. ( 0.2 mathrm{A} )
12
162When a voltage source that is inducing voltage into a large number of coils is disconnected, and a switch that is in
series with the coils of wire is also
opened, a spark is observed to jump across the switch terminals as the
switch begins to open up. Identify the cause of this spark?
A. Free electrons from the voltage source
B. Free electrons from the coils of wire
c. collapse of the magnetic field in the coils
D. Secondary electron flow from the source
E. Stored voltage in the coils of wire
12
163If the voltage applied to a motor is 200
volt and back emf is 160 volt, then the
efficiency of the motor will be :
A. ( 100 % )
B. 80%
c. ( 50 % )
D. 25%
12
164A coil of inductance ( 1 H ) and resistance
( 10 Omega ) is connected to a resistanceless
battery of emf ( 50 V ) at time ( t=0 . ) The
ratio of the rate at which magnetic energy is stored in the coil to the rate at
which energy is supplied by the battery
at ( t=0.1 s ) is ( frac{37}{n} . ) Find ( x )
12
165Dimension of ( frac{text { magnetic flux }}{text { electric flux }} ) are
( mathbf{A} cdotleft[L T^{-1}right] )
B cdot ( left[T L^{-1}right] )
( mathbf{c} cdotleft[L^{3} T^{2} A^{-2}right] )
D cdot ( left[L^{0} T^{0} A^{0}right] )
12
166What is an a.c. generator or Dynamo
used for? Name the principle on which it
works.
12
167A semicircular wire of radius ( boldsymbol{R} ) is
rotated with constant angular velocity about an axis passing through one end and perpendicular to the plane of the wire. There is a uniform magnetic field
of strength ( B ). The induced emf between
the ends is
( mathbf{A} cdot B omega R^{2} / 2 )
в. ( 2 B omega R^{2} )
C. is variable
D. none of these
12
168Which of the following is/are correct statement(s)?
This question has multiple correct options
A. The motional EMF generated by a magnetic force on a moving wire is case of Lorentz force
B. The transformer EMF generated by an electric force due to a changing magnetic field is the result of Faraday law.
C. The motional EMF generated by a magnetic force on a moving wire is case of Faraday’s law.
D. Both B and C are correct.
12
169A coil has self inductance of 0.01 H. The
current through it is allowed to change
at the rate of ( 1 A ) in ( 10^{-2} ) s. The induced
emf is
A . ( 1 V )
B. 2
( c .3 V )
D. ( 4 V )
12
170When a coil rotated in magnetic field
induced current in it :
A. continuously changes
B. remains same
c. becomes zero
D. becomes maximum
12
171Identify which of the following best
describe the Mutual inductance?
A. the ability of a current carrying conductor to induce a voltage in another conductor through a mutual magnetic field.
B. the ability of current carrying conductor to produce a changing magnetic field.
C. the ability of a conductor to induce a magnetic field in another current carrying conductor
D. the ability of a current carrying conductor to induce a current in another conductor through a mutual magnetic field.
E. the ability of a magnetic field to induce a voltage in a current carrying conductor.
12
172The wire is found to vibrate in the third
harmonic.The time when the emf
becomes maximum for the first time is
A ( cdot frac{2 pi}{omega} )
B. ( frac{pi}{omega} )
c. ( frac{pi}{2 omega} )
( D cdot 2 pi )
1
12
173A 50 turn circular coil has a radius of 3
( mathrm{cm}, ) it is kept in a magnetic field acting normal to the area of the coil. The
magnetic field B is increased from ( 0.10 T ) to ( 0.35 T ) in 2 milli second, the
average induced emf will be
A. ( 177 V )
B. ( 1.77 V )
c. ( 0.177 V )
D. ( 17.7 V )
12
174The production of an electromotive force across an electrical conductor in a
changing magnetic field is known as an Electromagnetic induction. Enter 1 for True and 2 for False.
12
175A rectangular loop of wire of size ( 4 c m times 10 c m ) carries steady current of
2 A. A straight long wire carrying 5 A current is kept near the loop as shown. If the loop and the wire are coplanar, find the magnetic flux through the
rectangular loop.
12
176The frequency of generator ( (mathrm{AC}) ) is measured using:
A. multimeter
B. AVO meter
c. tachometer
D. speedometer
12
177From which of the following case, the
induced current in the loop will not be
obtained?
A. The loop is moved in the direction of the magnet
B. The loop and magnet are moved in the opposite direction with the same speed
C. The magnet is moved in the direction of the loop
D. The loop and magnet are moved in one direction with the same speed
12
178A transformer has 50 turns in primary and 100 turns in secondary. If the primary is connected to 220 V d.c.
supply, then the voltage across the secondary will be :
A . ( 440 mathrm{V} )
B. 220
( c cdot 110 v )
D. o v
12
179Mark the incorrect statement.
A. electric current produces magnetism.
B. magnets can produce electric current.
C. magnets can’t produce electric current.
D. a and b
12
180Dynamo produces:
A. Charge
B. Electromotive force
C . Electric field
D. Magnetic field
12
181When the number of turns per unit length in a solenoid is doubled then its
coefficient of self induction will become
A . half
B. double
c. four times
D. unchanged
12
182Two circular coils can be arranged in
any of three situations as shown in the
figure. Their mutual inductance will be:
A. maximum in situation (i)
B. maximum in situation (ii)
c. maximum in situation (iii)
D. same in all situation
12
183A thin wire of length ( 2 m ) is
perpendicular to the ( x-y ) plane. It is
moved with velocity ( overrightarrow{boldsymbol{v}}=(2 hat{boldsymbol{i}}+boldsymbol{3} hat{boldsymbol{j}}+ )
( hat{k}) m / s ) through a region of magnetic induction ( vec{B}=(hat{i}+2 hat{j}) W b / m^{2} . ) Then
potential difference induced between the ends of the wire is
A . ( 2 V )
B. ( 4 V )
( c .0 V )
D. none of these
12
184The phenomena of a electromagnetic
induction is
A. The process of charging a body
B. The process of generating magnetic field due to current passing through a coil
C. Producing induced current in a coil due to relative motion between a magnet and a coil
D. All the above
12
185The Sl unit of inductance, the henry, can
be written as :
This question has multiple correct options
A. weber / ampere
B. volt second / ampere
C . joule / ampere ( ^{2} )
D. ohm second
12
186In figure, there is a conducting ring having resistance ( R ) placed in the plane
of paper in a uniform magnetic field ( B_{0} ) If the ring is rotating in the plane of paper about an axis passing through
point ( boldsymbol{O} ) and perpendicular to the plane
of paper with constant angular speed ( omega ) in clockwise direction, then
A. point ( O ) will be at higher potential than ( A )
B. the potential of point ( B ) and ( C ) will different
c. the current in the ring will be zero
D. the current in the ring will be ( 2 B_{0} omega r^{2} / R )
12
187A transformer core is laminated to
A. reduce hysteresis loss
B. reduce eddy current loss
c. reduce copper loss
D. reduce all of the above loss
12
188In the magnet and coil experiment, the magnet and the coil are moved in the same direction with same speed, the
emf induced in the coil is
A. Maximum
B. Minimum
c. Either (1) or (2)
D. zero
12
189An equilateral triangular conducting
frame is rotated with angular velocity ( omega )
in uniform magnetic field ( B ) as shown.
Side of triangle is ( l ). Choose the correct
options
This question has multiple correct options
A. ( V_{a}-V_{c}=0 )
B. ( v_{a}-V_{c}=frac{B omega l^{2}}{2} )
c. ( _{V_{a}-V_{b}}=frac{B omega l^{2}}{2} )
D. ( V_{c}-V_{b}=-frac{B omega l^{2}}{2} )
12
190A ( 100 m H ) coil carries ( 1 A ) current.
Energy stored in its magnetic field is.
A. 0.15
J ( 5.1 .5 . )
B. ( 0.05 J )
( c .0 .5 J )
D. ( 1 . )
12
191A rectangular coil has 60 turns and its length and width is ( 20 mathrm{cm} ). and ( 10 mathrm{cm} ) respectively. The coil rotates at a speed
of 1800 rotation per minute in a
uniform magnetic field of ( 0.5 T ) about its one of the diameter. Calculate
maximum induced emf will be
12
192The value if power ( boldsymbol{P}_{2} ) is
A. ( 10000 W )
B. ( 975 W )
( c .25 W )
D. ( 200 W )
12
1931,2,3 and 4 are the four stages of ( a ) rotating armature coil placed between the poles of a filed magnet.
(a) In which stage / stages will the emf be maximum?
(b) Represent graphically the relation between induced emf and angle of
rotation of the coils in stages 1,2,3 and
4
12
194A small magnet M is allowed to fall
through a fixed horizontal conducting ring R. Let ( g ) be the acceleration due to gravity. The acceleration of M will be This question has multiple correct options
A. ( g when it is above R and moving towards R
c. g ) when it is below ( R ) and moving away from ( R )
12
195A uniform magnetic field of induction ( boldsymbol{B} )
is confined to a cylindrical region of radius ( R ). The magnetic field is
increasing at a constant rate of ( boldsymbol{d B} / boldsymbol{d t T} )
( s^{-1} . ) An electron placed at the point ( P ) on the periphery of the field, experiences an acceleration:
( ^{mathbf{A}} cdot frac{1}{2} frac{e R}{m} frac{d B}{d t} ) toward left
B. ( frac{1}{2} frac{e R}{m} frac{d B}{d t} ) toward right
c. ( frac{e R}{m} frac{d B}{d t} ) toward left
D. zero
12
196What will be the self inductane of a coil
of 100 turns if a current of ( 5 A ) produces
a magnetic flux ( 5 times 10^{-5} ) Wb?
( mathbf{A} cdot 1 m H )
в. ( 10 mathrm{mH} )
( c cdot 1 mu H )
D. ( 10 mu H )
12
197The polarity of induced emf is given by
A. Ampere’s circuital law
B. Biot-Savant’s law
C. Lenz’s law
D. Remlng’s right hand rule
E. Flemhg’s left hand rule
12
198A metal disc of radius R rotates with an
angular velocity, ( omega=1 r a d / s ) about an
axis perpendicular to its plane passing through its centre in a magnetic field of induction B acting perpendicular to the plane of the disc. The induced e.m.f. between the rim and axis of the disc is:
A ( . B R^{2} )
B ( cdot 2 B^{2} R^{2} )
( c cdot B R^{3} )
D. ( B R^{2} / 2 )
12
199When the plane of the armature of an
a.c generator is parallel to the field, in which it is rotating
A. both the flux linked and induced emf in the coil are zero
B. the flux linked with it is zero, while induced emf is maximum
c. flux linked is maximum while induced emf is zero
D. both the flux and emf have their respective maximumm values
12
200What is eddy current? Mention two
applications of eddy current.
12
201A bar magnet is moved along the axis of a copper ring placed far away from the magnet. Looking from the side of the magnet, an anti-clockwise current is
found to be induced in the ring. Which
of the following may be true? This question has multiple correct options
A. The south pole faces the ring and the magnet moves towards it
B. The north pole faces the ring and the magnet moves towards it.
c. The south pole faces the ring and the magnet moves away from it.
D. The north pole faces the ring and the magnet moves away from it.
12
202The phenomenon of electromagnetic
Induction is :
A. The process of charging a sphere
B. The process of producing magnetic field in a coil
C. The process of producing induced current in a coil whenever there is a relative motion between the coil
and the magnet
D. The process of producing cooling effect
12
203The induced voltage across a stationary conductor in a stationary magnetic field is
A. zero
B. reversed in polarity
c. increased
D. decreased
12
204The magnetic field ( B=2 t^{2}+4 t^{2} )
(where ( t= ) time ) is applied perpendicular to the plane of a circular wire of radius ( r ) and resistance ( R ). If all
the units are in SI the electric charge that flows through the circular wire during ( t=0 s ) to ( t=2 s ) is
A ( cdot frac{6 pi r^{2}}{R} )
в. ( frac{24 pi r^{2}}{R} )
c. ( frac{32 pi r^{2}}{R} )
D. ( frac{48 pi r^{2}}{R} )
12
205The conductor AD moves to the right in a uniform magnetic field directed into
the paper:
( (x) )
This question has multiple correct options
A. The free electrons in AD will move towards A
B. D will acquire a positive potential with respect to A
C. If ( D ) and ( A ) are joined by a conductor externally, a current will flow from A to D in AD
D. The current in AD flows from lower to higher potential
12
206At the instant when the current in an
inductor is increasing at a rate of ( mathbf{0 . 0 6 4 0} boldsymbol{A} / boldsymbol{s}, ) the magnitude of the self-
induced emf is ( 0.0160 V . ) If the inductor
is a solenoid with 400 turns, what is the
average magnetic flux through each turn when the current is ( 0.720 A ? )
12
207A magnet is taken towards a conducting ring in such a way that a constant current of ( 10 m A ) is induced in
it. The total resistance of the ring is
( 0.5 Omega . ln 5 s, ) the magnetic flux through
the ring changes by
( mathbf{A} cdot 0.25 m W b )
B. ( 25 m ) Wb
( mathbf{c} .50 m W b )
D. ( 15 mathrm{m} mathrm{Wb} )
12
208A coil with an area of ( 0.50 m^{2} ) and a
resistance of 7 ohms is completely in a changing magnetic field. If the current in the coil is 2.0 Amps,
what is the rate of change of the magnetic field?
A. ( 3.5 T / s )
в. ( 7 T / s )
c. ( 14 T / s )
D. ( 28 T / s )
12
209Th circular arc (in ( x-y ) plane) shown in
figure rotates (about ( z- ) axis ) with a
constant angular velocity ( omega . ) Time in a
cycle for which there will be induced
emf in the loop is:
A ( cdot frac{pi}{2 omega} )
B. ( frac{pi}{omega} )
c. ( frac{2 pi}{3 omega} )
D. ( frac{3 pi}{2 omega} )
12
210A loop of area ( 0.5 m^{2} ) is placed in a
magnetic field of strength ( 2 T ) in
direction making an angle of ( 30^{circ} ) with the field. The magnetic flux linked with the loop will be
A ( cdot frac{1}{2} W b )
в. ( sqrt{frac{3}{2}} W b )
c. ( 2 mathrm{Wb} )
D. ( frac{sqrt{3}}{2} W b )
12
211541
negligible resistance and radius ( a ). It is
hinged at the center of the ring and
direction with a uniform angular
velocity ( omega . ) There is a uniform magnetic
field of strength ( B ) pointing inward and
( r ) is a stationary resistance. Then
This question has multiple correct options
A. current through ( r ) is zero
B. current through ( r ) is ( left(2 B omega a^{2}right) / 5 r )
c. direction of current in external resistance ( r ) is from
center to circumference
D. direction of current in external resistance ( r ) is from
circumference to center
12
212In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes
are
A. friction and windage losses
B. copper losses
c. hysteresis and eddy current losses
D. none of the above
12
213In the circuit shown (fig), the coil has inductance and resistance. When X is
joined to ( Y ), the time constant is ( tau ) during the growth of current. When the
steady state is reached, heat is
produced in the coil at a rate P. ( X ) is now joined to Z. After joining ( X ) and ( Z )
A. the total heat produced in the coil is ( P tau )
B. the total heat produced in the coil is ( frac{1}{2} P tau )
( c . ) the total heat produced in the coil is ( 2 P tau )
D. the data given are not sufficient to reach a conclusion
12
21443. A rectangular loop of sides a and b is placed in xy plane.
A very long wire is also placed in xy plane such that side
of length a of the loop is parallel to the wire. The distance
between the wire and the nearest edge of the loop is d.
The mutual inductance of this system is proportional to
(a) a
(b) b
(c) 1/d
(d) current in wire
12
21577. An inductor coil stores 32 J of magnetic field energy
and dissipates energy as heat at the rate of 320 W when
a current of 4 amp is passed through it. Find the time
constant of the circuit when it is formed across an ideal
battery.
(a) t= 0.2 sec
(b) t= 0.32 sec
(c) T=0.5 sec
(d) t= 1 sec
12
216The current flowing in the circuit is
( mathbf{A} cdot 2.5 A )
B. ( 5 A )
( c cdot 1 A )
( mathbf{D} cdot 2 A )
12
217A proton of mass ‘m’ moving with a
speed ( v(<<c, ) velocity of light in vacuum) completes a circular orbit in time 'T' in a uniform magnetic field. If
the speed of the proton is increased to ( sqrt{2} v, ) what will be time needed to
complete the circular orbit?
A ( cdot sqrt{2} T )
в. T
c. ( frac{T}{sqrt{2}} )
D. ( frac{T}{2} )
12
218A proton (mass ( m ) ) accelerated by a
potential difference ( V ) files through a
uniform transverse magnetic filed ( boldsymbol{B} )
The field occupies a region of space by
width ‘ ( d^{prime} . ) If ( ^{prime} alpha^{prime} ) be the angle of deviation
of proton from initial direction of motion
(see figure), the value of ( sin alpha ) will be
A ( cdot frac{B}{2} sqrt{frac{e d}{m V}} )
B. ( e V sqrt{frac{B d}{2 m}} )
( ^{c} cdot frac{B}{2} sqrt{frac{e}{2 m V}} )
D ( cdot B d sqrt{frac{e}{2 m V}} )
12
219What determines the frequency of a.c.
produced in a generator?
A. The number of rotations of the coil in one second.
B. the speed of rotation of the coil
( c cdot ) both ( A & B )
D. None of the above
12
220Work done by all forces in ring in 0 to
( left(frac{n}{omega}right) ) time interval is
( A )
в. ( frac{1}{8} frac{left(B_{0} Q Rright)^{2}}{m} )
c. ( frac{1}{4} frac{left(B_{0} Q Rright)^{2}}{m} )
D. ( frac{1}{2} frac{left(B_{0} Q Rright)^{2}}{m} )
12
221In a transformer, coefficient of mutual
inductance between primary and secondary coil is ( 0.2 mathrm{H} ). When current changes by 5 Na in the primary, then:
the induced era in the secondary will be
A. ( 0.5 mathrm{v} )
B. 1
( c cdot 1.5 v )
D. 2.0
12
222Draw a neat diagram of AC dynamo and represent the current in it in the
external circuit by a graph.
12
223Figure shows a square loop of side ( 5 mathrm{cm} )
being moved towards right at a
constant speed of ( 1 mathrm{cm} / mathrm{sec} ). The front
edge just enters the ( 20 mathrm{cm} ) wide
magnetic field at ( t=0 . ) Find the
induced emf in the loop at ( t=2 s ) and
( t=10 s )
12
224An equilateral triangle frame PQR of
mass ( mathrm{M} ) and side a is kept under the
influence of magnetic force due to inward perpendicular magnetic field B and gravitational field as shown in the
figure.The magnitude and direction of current in the frame so that the frame
remains at rest is
( A )
[
I=frac{2 M g}{a B} ; text { anticlockwise }
]
в.
[
I=frac{2 M g}{a B} ; text { clockwise }
]
( c )
[
I=frac{M g}{a B} ; text {anticlockwise}
]
( D )
[
I=frac{M g}{a B} ; text { clockwise }
]
12
225What does an electric generator
generate?
A. current
B. Magnetism
c. Gravity
D. Light
12
electromagnetic induction.
12
227A small generator is called a
A. AC generator
B. DC generator
c. Dynamo
D. All
12
228What amount of power is generated in
that resistance?
( P=frac{2 v^{2} B^{2} d^{2} R}{left(R+frac{2 rho d}{S}right)^{2}} )
( P=frac{2 v^{2} B^{2} d^{2} R}{left(R+frac{rho d}{S}right)^{2}} )
( mathbf{C} cdot p=frac{v^{2} B^{2} d^{2} R}{left(R+frac{2 rho d}{S}right)^{2}} )
( P=frac{v^{2} B^{2} d^{2} R}{left(R+frac{rho d}{S}right)^{2}} )
12
229toppr
generated across the coil during one
cycle is
( A )
B.
( c )
( D )
12
230The area of the coil must be.
A . ( 1.8 m^{2} )
B. ( 18 m^{2} )
( c cdot 8 m^{2} )
D. none of these
12
231A cyclist riding a bicycle fitted with dynamo to a tyre gets bright light from the bulb connected when he s fast. this
is because
A. magnet becomes powerful, when wheel rotates faster and current flows fast
B. current flows easly when cycle goes down
c. more magnetic lines of force change with respect to the coil and leading more current
D. coil become hot due to friction and produces more current
12
232A coil of cross-sectional area ( boldsymbol{A} ) having
( boldsymbol{n} ) turns is placed in a uniform magnetic
field ( B ). When it is rotated with an
angular velocity ( omega, ) the maximum e.m.f.
induced in the coil will be
( mathbf{A} cdot n B A omega )
В ( cdot frac{3}{2} n B A omega )
( c .3 n B A omega )
D. ( frac{1}{2} n B A )
12
233A machine is run such that electrical
current is input and as a result rotation is achieved in the rotor. If current is
turned off and rotation is forced in the
machine
A. current is produced
B. Rotor motion faces resisting force
c. Machine acts as a generator
D. All of the above
12
234Two concentric coils each of radius
equal to ( 2 pi mathrm{cm} ) are placed at right
angles to each other. 3 ampere and 4 ampere are the currents flowing in each coil respectively. The magnetic
induction in ( w e b e r / m^{2} ) at the centre of
the coils will be
( left(mu_{0}=4 pi times 10^{-7} w b / A . mright) )
A ( cdot 10^{-5} )
B . ( 12 times 10^{-5} )
C ( .7 times 10^{-5} )
D. ( 5 times 10^{-5} )
12
235allu
4. A conducting wire frame is placed in a magnetic field
which is directed into the paper. The magnetic field is
increasing at a constant rate. x
The directions of induced
current in wires AB and CD are x A x
(a) B to A and D to C
(b) A to B and C to D X BX
(c) A to B and D to C
(d) B to A and C to D
12
236Find the inductance ( L ) of a solenoid of
length I whose windings are made of material of density D and resistivity ( rho ) The winding resistance is ( mathrm{R} ) :
A ( cdot frac{mu_{0}}{4 pi l} cdot frac{R_{m}}{rho D} )
в. ( frac{mu_{0}}{4 pi R} cdot frac{l_{m}}{rho D} )
c. ( frac{mu_{0}}{4 pi l} cdot frac{R^{2} m}{rho D} )
D. ( frac{mu_{0}}{2 pi R} cdot frac{l_{m}}{rho D} )
12
237Two coils have self-inductance ( boldsymbol{L}_{mathbf{1}}=mathbf{4} )
( boldsymbol{m} boldsymbol{H} ) and ( boldsymbol{L}_{2}=mathbf{1} boldsymbol{m} boldsymbol{H} ) respectively. The
currents in the two coils are increased
at the same rate. At a certain instant of
time both coils are given the
same power. If ( i_{1} ) and ( i_{2} ) are the currents
in the two coils, at that instant of time
respectively, then the value of ( left(i_{1} / i_{2}right) ) is
A ( cdot frac{1}{8} )
в. ( frac{1}{4} )
( c cdot frac{1}{2} )
D.
12
238In one second, a current of 10 A changes through a coil. The induced emf is ( 10 v ) then, self-inductance of the coil is
A . २
B. 5H
c. ( 1 mathrm{H} )
D. 0.5H
12
239AUUU 2015
22. A metallic rod of length
‘l’ is tied to a string of
rotate with angular speed
O on a horizontal table
with one end of the string
fixed. If there is a vertical magnetic field ‘B’ in the region,
the e.m.f. induced across the ends of the rod is
3 Bol2
4 Bol?
2
(a)
(b)
=
2
5 Bol
(d) 2 Bor
(JEE Main 2013)
12
240The self inductance of a coil having 500 turns is 50 mH. The magnetic flux through the cross-sectional area of the coil while current through it is 8 mA is found to be
A ( cdot 4 times 10^{-4} W b )
в. ( 0.04 W b )
c. ( 4 mu W b )
D. ( 40 m W b )
12
241The co-efficient of mutual induction
between primray and secondary coil is
2H. Calculate induced e.m.f. if current of
4A is cut off in ( 2.5 times 10^{-4} ) seconds.
12
242An electrical generator works on the principle of electromagnetic induction
A. True
B. False
12
243A rectangular coil of single turn, having
area ( A, ) rotates in a uniform magnetic
field B with an angular velocity ( omega ) about an axis perpendicular to the field. If
initially the plane of the coil is perpendicular to the field, then the average induced emf when it has
rotated through ( 90^{circ} ) is:
( mathbf{A} cdot frac{omega B A}{pi} )
в. ( frac{omega B A}{2 pi} )
c. ( frac{omega B A}{4 pi} )
D. ( frac{2 omega B A}{pi} )
12
244( mathbf{A} )
D.C. generator is based on the
principle of
A. magnetic effect ofcurrent
B. lighting effect ofcurrent
c. electrochemical induction
D. electromagnetic induction
12
245( x )
cnanges Its pıtch so that It IS rIyıng
( 100 m / s ) in an area of the Earth’s
magnetic field that is perpendicular to
the plane and equal to ( 5.010^{5} T )

What is the emf induced between the
wing tips? Assume that the plane was previously flying parallel to the earths magnetic field.
A. ( 0.12 mathrm{v} )
B. 0.20
c. ( 1.2 v )
( D )

12
246Give reasons for the following. Split rings are used instead of slip rings to construct DC dynamo.12
247A thin semicircular conducting ring of
radius ( mathrm{R} ) is falling with its plane vertical
in a horizontal magnetic field B. At the
position MNQ, the speed of the ring is ( mathbf{v} ) and the potential difference across the
ring is
A. zero
B ( cdot frac{1}{2} B v pi R^{2} ) and ( mathrm{M} ) is at higher potential
( mathrm{c} . pi R B v ) and ( mathrm{Q} ) is at higher potential
D. ( 2 R B v ) and ( Q ) is at higher potential
12
248Find the induced emf about ends of the
rod in each case.
(ii)
12
249( A ) and ( B ) are two concentric circular
conductors of centre ( boldsymbol{O} ) and carrying
currents ( I_{1} ) and ( I_{2} ) as shown in the
1 : 2 and ratio of the flux densities at ( O )
due to ( A ) and ( B ) is ( 1: 3, ) then the value of
( boldsymbol{I}_{1} / boldsymbol{I}_{2} ) is:
12
250In an AC generator, maximum number of lines of force pass through the coil when the angle between the plane of coil and lines of force is12
251A ( 10 m ) long horizontal wire extends
from North East to South West. It is
falling with a speed of ( 5.0 m s^{-1}, ) at right angles to the horizontal component of the earth’s magnetic field, of ( 0.3 x ) ( 10^{-4} W b / m^{2} . ) The value of the induced
emf in wire is:
A ( cdot 2.5 times 10^{-3} V )
В. ( 1.1 times 10^{-3} V )
c. ( 0.3 times 10^{-3} V )
D. ( 1.5 times 10^{-3} V )
12
252Complete the following sentence:
The current is induced in a closed
circuit only if there is
A. change in number of magnetic field lines linked with the circuit.
B. no change in number of magnetic field lines linked with the circuit
C. change in number of gravitational field lines linked with the circuit.
D. no change in number of gravitational field lines linked with the circuit.
12
253Which one of the following can produce maximum induced emf?
A. 50 ampere DC
B. 50 ampere, ( 50 H z ) AC
c. 50 ampere, ( 500 mathrm{Hz} ) АС
D. 100 ampere DC
12
254A thin copper wire of length ( 100 mathrm{m} ) is wound as a solenoid of length ( l ) and radius ( r . ) Its self-inductance is
found to be L. Now if the same length of wire is wound as a solenoid of length ( l )
but of radius ( r / 2, ) then its self-
inductance will be :
A . ( 4 L )
B. 2L
( c cdot L )
D. L/2
12
255State whether given statement is True or False
A device which receives and then
transmits electromagnetic signal in an artificial satellite is called transponder.
A. True
B. False
12
256What energy conversion takes place in
a generator?
A. mechanical energy into magnetic energy.
B. mechanical energy into chemical energy.
C. mechanical energy into electric energy.
D. electrical energy into mechanical energy
12
257The conducting rod ( a b ), as shown in figure makes contact with metal rails
( c a ) and ( d b . ) The apparatus is in a uniform
magnetic field of ( 0.800 T, ) perpendicular to the plane of the figure. In what
direction does the current flow in the
rod?
( A cdot b ) to ( a )
B. a to
( c . ) a to b and then b to a
D. a to
12
258Assertion
When number of turns in a coil is
doubled, coefficient of self-inductance
of the coil becomes 4 times.
Reason
This is because ( L alpha N^{2} )
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
259An electromagnetic field exists only when there is
A. an increasing current
B. decreasing current
c. voltage
D. current
12
260A circular loop of radius ( boldsymbol{R} ), carrying
current ( I ), lies in ( x-y ) plane with its
center at the origin. The total magnetic
flux through ( x-y ) plane is
This question has multiple correct options
A. directly proportional to ( l )
B. directly proportional to ( R )
c. inversely proportional to ( R )
D. zero
12
261Two identical circular loops of metal wire are lying on a table without
touching each other. Loop – ( A ) carries a
current which increases with time. In
response, the loop-B
A. remains stationary
B. is attracted by the loop ( A )
c. is repelled by the loop ( A )
D. rotates about its ( C M ) with ( C M ) fixed
E. none of these
12
262The essential difference between an AC
generator and a DC generator is that:
A. AC generator has an electromagnet while a DC generator has permanent magnet.
B. DC generator will generate a higher voltage.
C. AC generator will generate a higher voltage.
D. AC generator has slip rings while DC generator has a commutator.
12
263( boldsymbol{y}=boldsymbol{x}^{4}, ) is moving with velocity ( boldsymbol{V}=boldsymbol{V}_{0} boldsymbol{i} )
in a non-uniform magnetic field ( vec{B}= )
( boldsymbol{B}_{0}left(1+left(frac{boldsymbol{y}}{boldsymbol{L}}right)^{beta}right) hat{boldsymbol{k}}, ) as shown in figure. If
( V_{0}, B_{0}, L ) and ( beta ) are positive constants
and ( Delta phi ) is the potential difference
developed between the ends of the wire,
then the correct statement(s) is/are?
This question has multiple correct options
A ( cdot|Delta phi|=frac{4}{3} B_{0} V_{0} L ) for ( beta=2 )
B. ( |Delta phi| ) remains same if the parabolic wire is replaced by a straight wire, ( y=x, ) initially, of length ( sqrt{2} l )
C ( cdot|Delta phi|=frac{1}{2} B_{0} V_{0} L ) for ( beta=0 )
D. ( |Delta phi| ) is proportional to the length of wire projected on y-axis
12
264Read the following statements and answer whether the given statement is true or false.

The number of magnetic lines of force passing through a surface is called magnetic flux linked with that surface.
A. True
B. False

12
265The magnetic flux linked with a coil is changing with time ( t(text { second }) ) according to ( phi=6 t^{2}-5 t+1 . ) Where ( phi ) is in ( mathrm{Wb} )
At ( t=0.5 mathrm{S}, ) the induced current in the
coil is

The resistance
of the circuit is ( 10 Omega )
A . 1 A
B. 0.1A
c. ( 0.1 mathrm{mA} )
D. 10A

12
perpendicular to a constantmagnetic
field of magnitude ( 1 mathrm{T} ) as shown in figure. One end of a resistanceless rod is
hinged at thecentre of ring 0 and other
end is placed on the ring. Now rod is rotated with constant angular velocity ( 4 mathrm{rad} / mathrm{s} ) by some external agent and circuit is connected as shown in the
figure, initially switch is open andcapacitor is uncharged. If switch S
is closed at ( t=0, ) then calculate heat
( operatorname{loss}(operatorname{in} mu mathrm{J}) ) from the resistor ( boldsymbol{R}_{1} ) from ( mathrm{t} )
( =0 ) to the instant when voltage across the capacitor becomes half of steady state voltage. (Assume plane of ring to be horizontal and friction to be absent
at all the contacts)
12
267Electromagnetic induction is not used
in
A. Transformer
B. Room heater
c. Ac generator
D. Choke coil
12
268Which of the following statements is
not correct?
A. Whenever the amount of magnetic flux linked with a circuit changes, an emf is induced in the circuit.
B. The induced emf lasts so long as the change in magnetic flux continues.
C. The direction of induced emf is given by Lenz’s law.
D. Lenz’s law is a consequence of the law of conservation of momentum.
12
269BN
59. The magnetic induction at P, for the arrangement shown
in the figure, when two similar
short magnets of magnetic
moment M are joined at the
middle so that they are
mutually perpendicular will
be
(b) Ho 3M
4T
²
(a) Ho M√3
41 d3
(c) Ho MV5
41 ď
(d) M2M
41 d3
12
270The laws of electromagnetic induction have been used in the construction of a
A. galvanometer
B. voltmeter
c. electric motor
D. electric generator
12
271Calculate the induced emf in the loop if
the current in both the wires is
changing at the rate ( boldsymbol{d} boldsymbol{i} / boldsymbol{d} boldsymbol{t} )
12
272The number of turns in a coil of wire of
fixed radius is 600 and its self
inductance is 108 mH. The self
inductance of a coil of 500 turns will be
A. 74 mH
B. 75 mH
c. ( 76 mathrm{mH} )
D. 77 mH
12
273A coil having an area ( A_{0} ) is placed in a
magnetic field which changes from ( boldsymbol{B}_{mathbf{0}} )
to ( 4 B_{0} ) in time interval t. The e.m.f.
induced in the coil will be
A ( cdot 3 A_{0} B_{0} / t )
в. ( 4 A_{0} B_{0} / t )
c. ( 3 B_{0} / A_{0} t )
D ( cdot 4 A_{0} / B_{0} t )
12
274What is back emf in a DC motor?12
275Two coils of self inductances ( 6 m H ) and
( 8 m H ) are connected in series and are
adjusted for highest co-efficient of coupling. Equivalent self inductance ( L )
for the assembly is approximately
( mathbf{A} cdot 50 m H )
в. ( 36 m H )
( mathrm{c} cdot 28 m H )
D. ( 18 m H )
12
276The inductance is measured in
A. ohm
c. henery
D. none of these
12
277In which of the following cases does the electromagnetic induction occur?
This question has multiple correct options
A. A current is started in a wire held near a loop of wire.
B. The current is stopped in a wire held near a loop of wire
C. A magnet is moved through a loop of wire.
D. A loop of wire is held near a magnet
12
278The current in a coil changes from ( 1 m A ) to ( 5 m A ) in 4 milli second. If the
coefficient of self-induction of the coil is
( 10 m H ) the magnitude of the “self-
induced” emf is:
A . ( 10 mathrm{mV} )
B. ( 5 mathrm{mV} )
c. ( 2.5 mathrm{mV} )
D. ( 1 mathrm{mV} )
12
2791. The inductance between A and
D is
(a) 3.66 H (b) 9 H
(c) 0.66 H (d) 1H
(AIEEE 2002)
12
280U
TO
69. A bar magnet was pulled away from a hollow coil A as she
in figure. As the south pole came out of the coil, the
magnet next to hollow coil B experienced a magnetic force
Up
Left
Right
Down
I NORDS
(a) to the right
(c) upward
(b) to the left
(d) equal to zero
12
281A generator has an e.m.f. of 440 volt and internal resistance of 400 ohm. Its
terminals are connected to a load of
4000 ohm. The voltage across the load
is:
A . 220volt
B. 440volt
c. ( 200 v o l t )
D. 400volt
12
282Figure as shown a rod ( P Q ) of length
( 20.0 mathrm{cm} ) and mass ( 200 mathrm{g} ) suspended through a fixed point ( O ) by two threads
of length ( 20.0 mathrm{cm} ) each. A magnetic field
of strength ( 0.500 T ) exists in the vicinity
of the wire ( P Q ) as shown in the figure.
The wires connecting with ( P Q ) with the battery are loose and exert no force on
( P Q )
(a) Find the tension in the threads when
the switch ( S ) is open.(b) A current of
( 2.0 A ) is established when the switch ( S )
is closed. Find the tension in the thread.
12
283The net magnetic flux through any closed surface, kept in a uniform magnetic field is?
A. zero
в. ( frac{mu_{o}}{4 pi} )
c. ( 4 pi mu_{o} )
D. ( frac{4 mu_{o}}{pi} )
12
284Magnitude of e.m.f. produced in a coil when a magnet is inserted into it does
not depend upon:
A. Number of turns in the coil
B. Speed of the magnet
c. Magnetic strength of magnet
D. Temperature of coil
12
285A wooden stick of length ( 3 l ) is rotated
about an end with constant angular velocity ( omega ) in a uniform magnetic field ( B ) perpendicular to the plane of motion. If the upper one-third of its length is coated with copper, the potential difference across the whole length of the stick is
( A )
[
frac{9 B omega l^{2}}{2}
]
в.
[
frac{4 B omega l^{2}}{2}
]
c.
[
frac{5 B omega l^{2}}{2}
]
D.
[
frac{B omega l^{2}}{2}
]
12
286f cross section area and length of a long solenoid are increased 3 times then its
self-inductance will be changed how
many times-
A.
B. 2
( c cdot 3 )
( D )
12
287At large distances from source ( vec{E} ) and ( vec{B} )
are in phase and the decrease in their magnitude is comparatively slower with distance r as per
A ( cdot r^{-1} )
B.
( c cdot r^{-3} )
D ( cdot r^{2} )
12
288A loop of area ( 4 m^{2} ) is placed flat in the
x-y plane.There is a constant magnetic field ( 4 hat{j} ) in the region. Find the flux through the loop
A . 2 units
B. 4 units
c. 6 units
D. 0 units
12
289Which of the following statement is
correct?
This question has multiple correct options
A. when the magnetic flux linked with conducting loop is zero then emf induced is always zero
B. when the emf induced in conducting loop is zero, then the magnetic flux linked with the loop must be zero
C. transformer works on mutual induction
D. all of these
12
290A constant current i is maintained in a
solenoid. Which of the following
quantities will increase if an iron rod is inserted in the solenoid along its axis? This question has multiple correct options
A. Magnetic field at the centre
B. Magnetic flux linked with the solenoid
c. self-inductance of the solenoid
D. Rate of Joule heating
12
291A frame ( C D E F ) is laced in a region
where a magnetic field ( vec{B} ) is present. ( mathbf{A} )
rod of length one metre moves with
constant velocity ( 20 m / s ) and strength
of magnitude field is one tesia. The
power spent in the process is (take
( R=0.2 Omega ) and all other wires and rod
have zero resistance)
( mathbf{A} cdot 1 k W )
( mathbf{B} cdot 2 k W )
( mathbf{c} .3 k W )
( mathbf{D} cdot 4 k W )
12
292The back emf in a DC motor is
maximum when
A. the motor has picked up maximum speed.
B. the motor has just started moving.
C. the speed of motor is still on increase.
D. the motor has just been switched off.
12
293Figure shows a square loop of resistance ( 1 Omega ) of side ( 1 m ) being moved towards right at a constant speed of 1 ( boldsymbol{m} / boldsymbol{s} ). The front edge enters the ( boldsymbol{3} boldsymbol{m} )
wide magnetic field ( (B=1 T) ) at ( t=0 )
Draw the graph of current induced in
the loop as time passes. (Take anticlockwise direction of current as
positive)
[
x
]
12
294From which of the following case, the
current in the loop will not be induced?
A. The loop is moved in the direction of the magnet.
B. The magnet is moved in the direction of the loop.
C. The loop and magnet are moved in the opposite direction with the same speed.
D. The loop and magnet are moved in one direction with the same speed.
12
295A square metal loop of side ( 10 mathrm{cm} ) and
resistance ( 1 Omega ) is moved with a
constant velocity partly inside a uniform magnetic field of ( 2 W b m^{-2} )
directed into the paper, as shown in the
figure. The loop is connected to a
network of five resistors each of value
( 3 Omega ). If a steady current of 1 m ( A ) flows in
the loop, then the speed of the loop is
A ( cdot 0.5 mathrm{cms}^{-1} )
B. ( 1 mathrm{cms}^{-1} )
( mathrm{c} cdot 2 mathrm{cms}^{-1} )
D. ( 4 mathrm{cms}^{-1} )
12
296When a conducting ring is moved in a magnetic field then the total charge induced in it depends on
A. initial magnetic flux
B. final magnetic flux
c. the rate of change of magnetic flux
D. the total change in magnetic flux
12
297Explain in detail the principle, construction and working of a single phase AC generator.12
298A conducting rod of length Lis falling with velocity ( V ) in a uniform horizontal magnetic field B normal to the rod. The induced emf between the ends the rod
will be :
( A cdot 2 B V l )
B. zero
c. вlv
D. ( frac{B V l}{2} )
12
299If the number of turns and length of the long solenoid are doubled without
changing the area, then its self-
inductance ( L ) will be:
A . same
B. 2 times
c. 3 times
D. 4 times
12
What is ( y )
support. A uniform magnetic field of
( 0.4 T ) is directed perpendicular and into
the plane of the spring-rod system. At
( t=0, ) the rod is released with the
springs extended by ( 20 c m . ) If the spring
constant of each spring is ( 2 N m^{-1} )
then
This question has multiple correct options
A. the maximum value of emf induced across the rod is ( 64 m V )
B. the induced emf across the rod is reduced to zero in ( frac{pi}{8} ) S after releasing the rod.
C. the induced emf across the rod reaches maximum first time in ( frac{pi}{8} mathrm{S} ) after releasing the rod
D. the maximum value of induced emf is ( 32 m V )
12
301A wire as a parabola ( y=4 x^{2} ) is located
in a uniform magnetic field of inductance B perpendicular to the XY plane. At t=0 a connection starts
translation wise from the parabola apex
with constant acceleration ( alpha ). The
induced emf in the loop, thus formed, as a function of y is:
A ( e=sqrt{2 alpha} cdot B y )
( y )
в. ( e=B y sqrt{frac{alpha}{2}} )
c. ( e=frac{B y sqrt{a}}{2 sqrt{2}} )
D. ( e=frac{B y sqrt{alpha}}{4} )
12
302Assertion
When two coils are wound on each
other, the mutual induction between
the coils is maximum.
Reason
Mutual induction does not depend on
the orientation of the coils.
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
303Read the following statements and answer whether the given statement is true or false.
An electric generator works on the principle of electromagnetic induction
A. True
B. False
12
304A very long cylindrical wire of radius ( mathrm{R} )
carries a current ( boldsymbol{I}_{mathbf{0}} ) uniformly
distributed across the cross-section of
the wire, calculate the magnetic flux
through a rectangle that has one side of length w s running down the centre of the wire and another side of length ( R ),
shown in figure
A ( cdot frac{mu_{0} I_{0} times w R}{4 pi} )
B. ( frac{mu_{0} I_{0} w}{4 pi} )
с. ( frac{mu_{0} I_{0} R}{4 pi w} )
D. None of these
12
305Derive expression for self inductance of a long air-cored solenoid of length ( L )
cross- sectional area ( A ) and having number of turns N.
12
306A flat coil, ( C, ) of ( n ) turns, area ( A ) and
resisitance ( R ) is placed in a uniform
magnetic field of magnitude B. The plane of the coil is initially perpendicular to B. If the coil is rotated by an angle about the axis ( mathrm{XY} ), charge of amount Q flows through it. if the coil rotates about XY with a constant
angular velocity ( omega, ) the emf induced in
¡t.
This question has multiple correct options
A. is zero
B. changes nonlinearly with time
c. has a constant value ( =mathrm{BAn} omega )
D. has a maximum value ( = ) BAn
12
307A conduction loop of area ( 5 mathrm{cm}^{2} ) is
placed in a magnetic field which varies sinusoidally with time as ( B= )
( 0.2 sin 300 t . ) The normal to the coil
makes an angle of ( 60^{circ} ) with the field. The emf induced at ( t=(pi / 900) ) s is?
A ( .7 .5 times 10^{-3} mathrm{v} )
B. zero
c. ( 15 times 10^{-3} v )
D. ( 20 times 10^{-3} mathrm{V} )
12
308A coil of 100 turns and 5 square
centimeter is placed in a magnetic field
( mathrm{B}=0.2 mathrm{T} . ) The normal to the plane of the coil makes an angle of 60 with the direction of the magnetic field. The magnetic flux linked with the coil is :
A ( cdot 5 times 10^{-3} mathrm{wb} )
B. ( 5 times 10^{-5} mathrm{wb} )
( c cdot 10^{-2} w b )
D. ( 10^{-4} mathrm{wb} )
12
309What is an electromagnetic?12
310A magnetic field directed along ( Z ) axis varies as ( mathrm{B}=mathrm{BO} times mathrm{aB}=mathrm{BOxa} ) directed along
( X ) axis, the induced emf (in volts) in the
loop is
A . 3
B . 2
( c .5 )
D. 6
12
311A bar magnet moves toward two
identical parallel circular loops with a
constant velocity ( v ) as shown in figure
This question has multiple correct options
A. Both the loops will attract each other
B. Both the loops will repel each other
C. The induced current in ( A ) is more than that in ( B )
D. The induced current is same in both the loops
12
312A wire loop that encloses an area of ( 20 mathrm{cm}^{2} ) has a resistance of ( 10 Omega ). The
loop is placed in a magnetic field of ( 2.4 T ) with its plane perpendicular to the field. The loop is suddenly removed from
the field. How much charge flows past a given point in the wire?
( mathbf{A} cdot 12 times 10^{-4} C )
B. ( 10^{-1} C )
c. ( 4.8 times 10^{-4} C )
D. ( 2.4 times 10^{-3} C )
12
313Voltage in the secondary coil of a transformer does not depend upon:
A. frequency of the source
B. voltage in the primary coil
c. ratio of number of turns in the two coils
( D . ) both ( (b) ) and ( (c) )
12
314A square loop is placed in ( x-y ) plane
as shown in figure. Magnetic field in the region is ( vec{B}=-B_{0} x hat{k} . ) The induced
current in the loop is anticlockwise.
Reason
f inward magnetic field from such a loop increases, then current should be
anticlockwise
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
315X
X
1
X
X
X
X
X
34. A square non-conducting loop,
X X X X
20 cm, on a side is placed in a
(x x x x x x
magnetic field. The centre of side
(X x XOX X X
AB coincides with the centre of
magnetic field. The magnetic field
xxxx
is increasing at the rate of 2 T/s. The
potential difference between B and
D C
C is
(a) 30 m V
(b) zero
(c) 10 mV
(d) 20 mV
X
X
X
X
X
X
X
X
X
12
316toppr
Q туре уо
inductance to determine the height of the liquid level in the tank. The inductance of the tank changes from a
value of ( L_{0} ) corresponding to a relative permeability of 1 when the tank is
empty to value ( L_{f} ) corresponding to a
relative permeability ( boldsymbol{X}_{m} ) (relative permeability of liquid) when the tank is full. The appropriate electronic circuit can determine the inductance
correct upto 5 significant figures and thus the effective relative permeability of the combined air and liquid within the rectangular has height ( D ). The
height of the liquid level in the tank is ( d ) Ignore the fringing effects. Assume tank is fitted with ( boldsymbol{H} boldsymbol{g} boldsymbol{X}_{boldsymbol{H} boldsymbol{g}}=boldsymbol{2} . boldsymbol{9} times mathbf{1 0}^{5} )
Express ( d ) as a function of ( L ), inductance corresponding to a certain liquid height
( boldsymbol{L}_{0}, boldsymbol{L}_{f} ) and ( boldsymbol{D} )
A ( cdot d=frac{left(L-L_{0}right) D}{L_{f}-L_{0}} )
в. ( _{d}=frac{L D}{L_{f}-L_{0}} )
c. ( _{d=} frac{left(L-L_{0}right) D}{L_{f}} )
D. None of these
12
317The inductive reactance of a coil of
( 0.2 H ) inductance at a frequency of
( mathbf{6 0} boldsymbol{H} boldsymbol{z} ) is:
A . ( 7.54 Omega )
в. ( 0.754 Omega )
c. ( 75.4 Omega )
D. ( 7.54 times 10^{-3} Omega )
12
318Pick up the correct statements:
This question has multiple correct options
A. The changing (with time) magnetic field need not be in existence at the location of induced electric field.
B. A uniform magnetic field increasing at constant rate, induces an electric field which is constant and non
conservative
C. Non zero force exerted by uniform and constant magnetic field on a moving charged particle does no work but always changes momentum of the particle.
D. All the above statements are wrong.
12
319A coil having resistance ( 20 Omega ) and inductance ( 2 H ) is connected to a
battery of emf ( 4.0 % ). Find (a) the current
at ( 0.20 s ) after the connection is made
and
(b) the magnetic field energy in the
coil at the instant
12
320In an a.c. generator the speed at which the coil rotates is doubled. How would
this affect the frequency of output
voltage?
A. frequency is doubled
B. frequency is halvedd
c. frequency remains same
D. cant say
12
321Assertion
The coil in the resistance boxes are
Reason
Thick wire is required in resistance box.
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
322Interpret ( mathrm{K}^{prime}-mathrm{K} )12
323The split-ring type commutator is used in generators to:
A. Convert AC to DC
B. Convert DC to ACC
c. Induce emf
D. Induce magnetism
12
324Ampere. A “S” shaped conducting rod AB consisting of two semicircles each of
radius ( r ) is placed in such a way that the
centre ( C ) of the conducting wire is at a
distance ( 2 r ) from the end of the wire.The
rod ( A B ) moves with velocity of ( 5 m s^{-1} )
along the direction of the current flow as shown in the figure. If the line joining
the ends of the rod makes an angle ( 60^{circ} )
with the wire then,
This question has multiple correct options
A. the emf induced between the ends of the rod is ( (ln 4) )
( mu V )
B. the end ( A ) is at higher potential than end ( B ).
c. the end ( A ) is at lower potential than end ( B ).
D. the emf induced between the ends of the rod is ( (ln 3) )
( mu V )
12
325A conducting rod ( P Q ) of length ( l=2 m )
is moving at a speed of ( 2 m s^{-1} ) making
an angle of ( 30^{circ} ) with its length.
uniform magnetic field ( B=2 T ) exists
in a direction perpendicular to the plane of motion. Then
( mathbf{A} cdot V_{P}-V_{Q}=8 V )
B. ( V_{P}-V_{Q}=4 V )
C ( . V_{Q}-V_{P}=8 V )
( mathbf{D} cdot V_{Q}-V_{P}=4 V )
12
3267. The figure shows four wire loops, with edge lengths of
either L or 2L. All four loops will move through a region
of uniform magnetic field B (directed out of the page) at
the same constant velocity. Rank the four loops according
to the maximum magnitude of the e.m.f. induced as they
move through the field, greatest first
(a) (x = £j)(&q=&)
(c) Ę > Ed > & > Ey (d) x < £; <& < En
12
327The magnitude of the induced electric field in the orbit at any instant of time during the time interval of the magnetic
field change, is
A ( cdot frac{B R}{4} )
в. ( frac{B R}{2} )
c. ( B R )
D. ( 2 B R )
12
328Assertion
An electric motor converts electrical
energy to mechanical energy.
Reason
The working of the motor is based on
mutual induction.
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
329A millivoltmeter is connected in parallel to an axle of the train running with a speed of ( 180 mathrm{km} / ) hour. If the vertical component of earth’s magnetic field is ( 0.2 times 10^{-4} W b / m^{2} ) and the distance
between the rails is ( 1 mathrm{m} ), then the
reading of voltmeter will be :
A ( cdot 10^{-2} ) volt
B. ( 10^{-4} ) volt
c. ( 10^{-3} ) volt
D. 1 volt
12
330describe briefly any one way of
inducing e.m.f.
12
331Find the induced emf. Will the induced
emf be time dependent?
12
332n a coil of resistance ( 100 Omega ), a current
is induced by changing the magnetic flux through it as shown in the figure.
The magnitude of change in flux through the coil is:
A ( .275 mathrm{Wb} )
В. ( 200 mathrm{Wb} )
( c .225 W b )
D. ( 250 mathrm{Wb} )
12
333YSICS
dqE
ILLUSTRATION 23.6 What is the mutual inductance of a sys
of coaxial cables carrying current in opposite direction
shown in figure. Their radii are a and b, respectively.
putran the anace of
12
334Read the following statements and answer whether the given statement is true or false.
S.I. unit of magnetic flux is weber. It is a vector quantity
A. True
B. False
12
335Explain the underlying principle and working of electric generator by drawing
a labelled diagram. What is the function of brushes?
12
336Which of the following units denotes the dimension ( frac{M L^{2}}{Q^{2}} ) where ( Q ) denotes the electric charge?
A ( cdot W b / m^{2} )
в. henry( (H) )
c. ( H / m^{2} )
D. weber ( (W b) )
12
337Assertion
An AC generator is which converts mechanical energy into electrical energy (alternating emf). It works on the principle of electromagnetic induction the magnet generates an emf (current)
in the coil.
Reason
The property of coil by which an emf is induced in it when the current flowing through it changes is mutual inductance
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
338Find the inductance of a solenoid of
length ( l_{0}, ) made of Cu windings of mass
m. The winding resistance is equal to ( R )
The diameter of solenoid ( <<l . rho_{0} ) is resistivity of Cu and ( rho ) is density of the
Cu.
( ^{text {A }} cdot frac{mu_{0} R m}{2 pi l_{0} rho rho_{0}} )
в. ( frac{mu_{0} R m}{4 pi l_{0} rho rho_{0}} )
c. ( frac{mu_{0} R m}{3 pi l_{0} rho rho_{0}} )
D. ( frac{2 mu_{0} R m}{3 pi l_{0} rho rho_{0}} )
12
339A coil of wire is placed in a changing magnetic field. If the number of turns in the coil is decreased, the voltage induced across the coil will
A. increase
B. decrease
c. remain constant
D. be excessive
12
connected to a resistance ( R ) and two
ideal inductors ( L_{1} ) and ( L_{2} ) through a
switch ( S ) as shown. There is no mutual
inductance between the two inductors.
The switch ( S ) is initially open. At ( t=0 )
the switch is closed and current begins
to flow. Which of the following options is/are correct?
This question has multiple correct options
A ( cdot ) At ( t=0, ) the current through the resistance ( R ) is ( frac{V}{R} )
B. After a long time, the current through ( L_{2} ) will be ( frac{V}{R} frac{L_{1}}{L_{1}+L_{2}} )
C. After a long time, the current through ( L_{1} ) will be ( frac{V}{R} frac{L_{2}}{L_{1}+L_{2}} )
D. The ratio of the currents through ( L_{1} ) and ( L_{2} ) is fixed at all times ( (t>0) )
12
341State Fleming’s right hand rule and give examples. Demonstrate the same with the help of an experiment.12
342A conductor of uniform resistance (per
unit length) bent in the form of an
equilateral triangle of side a. It is
enclosing on inward magnetic field ( vec{B}=B_{0} cos ^{2} omega t(-hat{k}) . ) Then
This question has multiple correct options
A ( cdot ) During ( 0<t<frac{pi}{2 omega} ) an clockwise current is induced in
the coil.
B. During ( 0<t<frac{pi}{omega} ) an anticlockwise current is induced
in the coil
C . During ( frac{pi}{2 omega}<t<frac{pi}{omega} ) an anticlockwise current flows
through it
D. During ( frac{pi}{omega}<t<frac{3 pi}{2 omega} ) a clockwise current flows through
it
12
343The current does not rise immediately
in a circuit containing inductance
A. because of induced emf
B. because of high voltage drop
c. because of low power consumption
D. because of joule heating
12
34413. A coil of wire having finite inductance and resistance
has a conducting ring placed coaxially within it. The
coil is connected to a battery at time t = 0, so that a time-
dependent current 1/(t) starts flowing through the coil.
If I (t) is the current induced in the ring. and B(t) is the
magnetic field at the axis of the coil due to 1 (t), then as
a function of time (t > 0), the product 12 (t) B(t)
(a) Increases with time
(b) Decreases with time
(c) Does not vary with time
(d) Passes through a maximum
12
345S.I. unit of Magnetic flux is:
A. ampere-meter
B. ampere ( m^{2} )
C. weber
D. weber ( / mathrm{m}^{2} )
12
346Two conducting rings ( P ) and ( Q ) of radi and ( r ) and ( 2 r ) rotate uniformly in opposite directions with centre of mass
velocities ( 2 mathrm{v} ) and ( mathrm{v} ) respectively on a conducting surface S. There is a uniform magnetic field of magnitude B perpendicular to the plane of the rings.
The potential difference between the
highest points of the two rings is
( A cdot(a) ) zer
( B cdot(b) 4 B v )
( c cdot(c) 8 ) Bv
D. (d)16 Bv
12
347State whether following statements are True or False:
(a) An electric motor converts mechanical
energy into electrical energy
(b) An electric generator works on principle of electromagnetic induction
(c) The field at the center of a long circular
coil carrying current will be parallel straight lines
(d) A wire with a green insulation is usually the live wire of an electric supply
12
348In electromagnetic induction, the induced E.M.F is independent of
A. Change of flux
B. Time
c. Tesla
D. weber
12
349Calculate velocity at time12
350A metal disc of radius ( a ) rotates with a
constant angular velocity ( omega ) about its axis. The potential difference between the center and the rim of the disc is ( boldsymbol{m}= ) mass of electron, ( boldsymbol{e}= ) charge on
electron)
( ^{mathrm{A}} cdot frac{m omega^{2} a^{2}}{e} )
B. ( frac{1 m omega^{2} a^{2}}{2} )
( ^{mathrm{c}} cdot frac{e omega^{2} a^{2}}{2 m} )
D. ( frac{e omega^{2} a^{2}}{m} )
12
351What is the direction of force on the loop if ( frac{d i}{d t} ) is positive12
352A magnetic field ( B=2 t+4 t^{2} ) (where
( t=text { time }) ) is applied perpendicular to
the plane of a circular wire of radius ( r )
and resistance ( R ). If all the units are in
( S I, ) the electric charge that flows
through the circular wire during ( t=0 s )
to ( t=2 s ) is:
( mathbf{A} cdot frac{6 pi r^{2}}{R} )
В. ( frac{20 pi r^{2}}{R} )
( ^{mathrm{c}} cdot frac{32 pi r^{2}}{R} )
D. ( frac{48 pi r^{2}}{R} )
12
353A long solenoid of diameter 0.1 m has
( 2 times 10^{4} ) turns per metre.At the centre of
the solenoid, a coil of 100 turns and
radius ( 0.01 m ) is placed with its axis coinciding with the solenoid axis.The
current in the solenoid reduces at a
constant rate to ( 0 A ) from ( 4 A ) in 0.05 s.
If the resistance of the coil is ( 10 pi^{2} Omega )
the total charge flowing through the coil during this time is.
( mathbf{A} cdot 32 pi mu C )
B. ( 16 mu C )
c. ( 32 mu C )
D. ( 16 pi mu C )
12
354What is the Si unit of magnetic flux, is it vector or scalar quantity?12
355A square loop of side ( b ) is rotated in a
constant magnetic field ( B ) at angular
frequency ( omega ) as shown in figure. What is
the emf induced in it?
( mathbf{A} cdot b^{2} B omega sin omega t )
( mathbf{B} cdot b B omega sin ^{2} omega t )
( mathbf{C} cdot b B^{2} omega cos omega t )
D. ( b^{2} B omega )
12
356A varying current in a coil change from
( 10 A ) to 0 in 0.5 sec. If the average emf
induced in the coil is ( 220 V ), the self
inductance of the coil is :
A . ( 5 H )
в. ( 6 H )
( c .11 H )
D. ( 12 H )
12
357n mutual induction
A: when current in one coil increases, induced current in neighbouring coil flows in the opposite direction
B: When current in one coil decreases,
induced current in neighbouring coil flows in the opposite direction
A. A is true, B is false
B. A and B are false
c. A and B are true
D. A is false, B is true
12
358If a spark is produced on removing the load from an AC circuit then the
element connected in the circuit is
A. high resistance
B. high capacitance
c. high inductance
D. high impedance
12
359Which of the following statement is
correct?
A. AC generator generates a higher voltage
B. DC generator generates a higher voltage
C. AC generator has a permanent magnet whereas a DC generator has an electromagnet
D. There is a split-ring commutator in a DC generator but not in an AC generator
12
360In a coil of resistance ( 10 Omega ), the induced
current developed by changing magnetic flux through it, is shown in figure as a function of time. The magnitude of change in flux through the coil in Weber is-
12
361In a motor, a rotor is fitted with the
armature that has current of 10 A. The
rotor rotates with angular speed of 3 rad/s.Magnetic field of magnitude 2 T varies in direction is such a way that it
is always perpendicular to the loop area If the rotor coil has ( N ) number of turns
and area of each loop is ( 0.45 m^{2} ) then
find the value ( N . ) Given that motor
consumes 2106 W power and there are
no losses.
12
362Explain ( e . f . ) due to a uniformly charged
plane sheet
12
363A conducting loop (as shown) has total
resistance ( R ). A uniform magnetic field
( B=gamma t ) is applied perpendicular to
plane of the loop where ( gamma ) is a constant
and ( t ) is time. The induced current
flowing through loop is:
( A )
B. ( frac{left(b^{2}-a^{2}right) gamma}{R} )
c. ( frac{left(b^{2}-a^{2}right) gamma t}{R} )
D. ( frac{left(b^{2}+a^{2}right) gamma}{R} )
12
364In a magnetic field of ( 0.05 T ) area of coil
changes from ( 101 mathrm{cm}^{2} ) to ( 100 mathrm{cm}^{2} )
without changing the resistance which
is ( 2 Omega . ) The amount of charge that flow during this period is
A ( .2 .5 times 10^{-6} mathrm{C} )
В. ( 2 times 10^{-6} C )
( mathbf{c} cdot 10^{-6} C )
D. ( 8 times 10^{-6} C )
12
365A current carrying infinitely long wire is kept along the diameter of a circular wire loop, without touching it. The correct statement(s) is(are)
This question has multiple correct options
A. The emf induced in the loop is zero if the current is constant
B. The emf induced in the loop is finite if the current is constant
c. The emf induced in the loop is zero if the current decreases at a steady rate.
D. The emf induced in the loop is finite if the current decreases at a steady rate
12
366In figure, the wires ( P_{1} Q_{1} ) and ( P_{2} Q_{2} ) are
made to slide on the rails with same
speed of ( 5 c m s^{-1} . ) In this region, a
magnetic field of ( 1 T ) exists. The electric
current in the ( 9 Omega ) resistance is
This question has multiple correct options
A. zero if both wires slide toward left
B. zero if both wires slide in opposite directions
C. ( 0.2 m A ) if both wires move toward left
D. ( 0.2 m A ) if both wires move in opposite directions
12
367If length of a solenoid is increased then
what change should be made on no. of turns to keep self inductance constant-
( A ). increase
B. remain same
c. decrease
D. none of these
12
368A horizontal metal wire is carrying an electric current from the north to the
south. Using a uniform magnetic field, it is to be prevented from falling under gravity. The direction of this magnetic field should be towards the
A . east
B. west
c. north
D. south
12
369What is self inductance of a coil when a
charge of current from 0 to 2 A in 0.05 second induces an emf of ( 40 mathrm{V} ) in it?
A . ( 1 mathrm{H} )
B. 2H
( c . ) зн
D. 44
12
370When the normal to a coil points in the direction of magnetic field (B), then flux is
A. a scalar quantity
B. a vector quantity
c. neither scalar nor vector
D. uncertain
12
371Read the following statements and answer whether the given statement is true or false.

The induced e.m.f. depends only on the
no of turns of the coil:
A. True
B. False

12
372Which of the following devices works on the principle of electromagnetic induction?
A. Ammeter
B. Voltmeter
c. Generator
D. Galvanometer
12
373The direction of the induced e.m.f. is
determined by :
A. Fleming’s left hand rule
B. Fleming’s right hand rule
c. Maxwell’s right hand screw rule
D. Ampere’s rule of swimming
12
374Assertion
The back emf in a dc motor is
maximum when the motor has just been switched on.
Reason
When motor is switched on it has
maximum speed.
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
375Assertion
Time-dependent magnetic field generates electric field
Reason
Direction of electric field generated
from time variable magnetic field does
obey Lenz’s 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. Assertion is incorrect but Reason is correct
12
376Self inductance of a long solenoid is directly proportional to(Where ( L ) is the length of solenoid)
A. ( L )
B . ( L^{2} )
c. ( 1 / L )
D. ( 1 / L^{2} )
12
377An induced emf has
A. A direction same as field direction
B. A direction opposite to the field direction
C. No direction of its own
D. Non of these
12
378( 10 c m ) and ( 100 c m ) are placed on a
horizontal plane as shown in the Figure.
Outer loop is connected to a source of
unknown emf through a key K. If a
current of ( 2 A ) flows in the inner loop as
shown aside, when the key k is closed at
time ( t=0 s, ) then the emf of the source
sending a current ( I ), should be
[Take resistance of both wire per length
( left.operatorname{as} 10^{-4} Omega m^{-1}right) )
of unknow
( mathbf{A} cdot 4 V )
B. ( 4 t V )
( mathbf{c} cdot 04 mathrm{t}^{2} mathbf{V} )
D. ( left(0.4 t^{2}+4 t+4right) V )
12
379Magnetic flux ( phi ) linked with a stationary loop of resistance ( R ) vaires with time ( t )
as ( phi=a t(T-t) . ) Amount of heat
generated in loop during time interval ( boldsymbol{T} )
is
( ^{mathbf{A}} cdot frac{a T}{3 R} )
( ^{mathbf{B}} cdot frac{a^{2} T^{2}}{3 R} )
c. ( frac{a^{2} T^{2}}{R} )
D. ( frac{a^{2} T^{3}}{3 R} )
12
380A conducting rod of length I and mass ( mathrm{m} ) is moving down a smooth inclined plane of inclination ( boldsymbol{theta} ) with constant
velocity ( v . ) A current ( i ) is flowing in the
conductor in a direction perpendicular to paper inward. A vertically upward magnetic field ( vec{B} ) exists in space. Then,
magnitude of magnetic field ( vec{B} ) is:
A ( cdot frac{m g}{i l} sin theta )
B. ( frac{m g}{i l} tan theta )
c. ( frac{m g cos theta}{i l} tan theta )
D. ( frac{m g}{text {ilsint}} )
12
381A horizontal magnetic field B is produced across a narrow gap between the two square iron pole pieces.
closed square loop of side a, mass ( mathrm{m} )
and resistance ( R ) is allowed to fall with
the top of the loop in the field. The loop
attains a terminal velocity equal to:
A ( cdot frac{R m g}{B^{2} a^{2}} )
B. ( frac{mu_{0}}{4 pi} frac{R m g}{B a^{2}} )
c. ( frac{m g B}{R a^{2}} )
D. ( frac{mu_{0}}{4 pi} frac{R m B}{B a^{2}} )
12
382The total magnetic induction at point 0
due to curved portions and straight portion in the following figure, will be
A ( cdot frac{mu_{0} i}{2 pi r}[pi-phi+tan phi )
в. ( frac{mu_{0} i}{2 pi r} )
c. ( frac{mu_{0} i}{pi r}[pi-phi+tan phi )
D.
12
383toppr
the rails is ( 1 m . ) A conducting rod of
mass ( 0.5 k g ) can slide on the rails
frictionlessly. The rod is tied at
midpoint to a light string passing over a smooth pulley fixed to the edge of the
table. A mass of 0.5kg tied to the other
end of the string hangs vertically as shown in the Figure. A uniform magnetic field of ( 0.5 T ) can be applied in
vertically downward direction. If the system is released from rest, then, point out incorrect statements from the
following:
I be the acceleration due to gravity]
This question has multiple correct options
A. When the magnetic field is put on, the acceleration of the system increases from ( frac{g}{3} ) to ( frac{g}{2} )
B. Due to induction, the change in the acceleration of the system is same as that obtained by increasing the mass of the rod by ( 0.5 k g ) in the absence of the magnetic field.
c. Due to induction, the change in the acceleration of the system is same as that obtained by decreasing the mass of the rod by ( 0.25 mathrm{kg} ) in the absence of magnetic field
D. When the magnetic field is put on, the acceleration of the system decreases from ( frac{g}{2} ) to ( frac{g}{3} )
12
true or false.

Energy stored in an inductor ( =frac{1}{2} L V^{2} )
A. True
B. False

12
385Ine varıatıon or anoae current ın a
triode valve corresponding to a change
in grid potential at three different
values of the plate potential is shown in
the given figure. The mutual
conductance of triode is
( mathbf{A} cdot 5 times 10^{-3} m h o )
B . ( 2.5 times 10^{-3} ) mho
C. ( 7.5 times 10^{-3} ) mho
D. ( 9.5 times 10^{-3} ) mho
12
386A copper wire of length ( l ) is bent into a
semicircle. It is moved with a velocity ( boldsymbol{v} ) in a region where magnetic field is uniform and perpendicular to the plane of the wire. If the strength of the field is
( B ) then emf induced is
( mathbf{A} cdot B l v )
в. ( quad B frac{l}{pi} v )
c. ( _{B} frac{2 l}{pi} v )
D. none of these
12
387A simple pendulum with bob of mass ( m ) and conducting wire of length L swings
under gravity through an angle ( 2 theta ). The
earth’s magnetic field component in the direction perpendicular to swing is B. The maximum potential difference
induced across the pendulum is?
12
388Match the statements in Column ( A )12
389Two ends of an inductor of inductance ( L )
are connected to two parallel
conducting wires. A rod of length ( l ) and
mass ( m ) is given velocity ( v_{0} ) as shown.
The whole system is placed in
perpendicular magnetic field ( B ). Find the maximum current in the inductor.
( ^{A} cdot frac{m v_{0}}{L} )
в. ( sqrt{frac{m}{L}} v_{0} )
c. ( frac{m v_{0}^{2}}{L} )
D. None of these
12
390Define coefficient of self inductance
and write its unit.
12
391An angular conductor is moving with
velocity ( v ) along its angular bisector in a
perpendicular magnetic field ( (B) ) as
shown in the figure. The induced potential difference between its free
ends will be
( A )
[
2 B v l sin frac{theta}{2} frac{theta}{2}
]
B. ( 2 B v l )
c. ( 2 B v l sin theta )
D. zero
12
392ILLUSTRATION 24.3 Suppose you want the current amplitude
in a pure inductor in a radio receiver to be 250 uA when the
voltage amplitude is 3.60 V at a frequency of 1.60 MHZ
(corresponding to the upper is 3.60 V AM broadcast band).
What inductive reactance is needed? What inductance is
required?
12
393State Faraday’s law of electromagnetic induction. Apply the law to obtain an expression for the induced emf in a conducting rod of length ( a ) rotating about its one end with angular velocity
( omega ) in uniform magnetic field B.
12
394If coil is placed perpendicular to field lines then number of lines passing
through coil are :
( A ). minimum
B. maximum
c. zero
D. may be max. or min
12
395Two coils ( A ) and ( B ) having turns 300 and 600 respectively are placed near each other, on passing a current of 3.0 ampere in ( A ), the flux linked with ( A ) is 1.2
( x 10^{-4} ) weber and with ( B ) it is ( 9.0 times 10^{-5} )
weber. The mutual induction of the
system is:
12
to two ideal voltmeters ( V_{1} & V_{2} )
Assume that a voltmeter reads ( Delta V= )
( -int_{a}^{b} vec{E} cdot d vec{ell} ) between its terminals. A time varying magnetic field ( B(t) ) exists in a circular region of radius a and it is
directed into the plane of the figure
( B(t)=B_{0} t ) where ( B_{0} ) is a positive
constant of proper dimensions and t is
the time. The emf induced in the circuit
is :
( A cdot 2 pi a^{2} B_{0} )
В ( cdot pi a^{2} B_{0} )
c. ( frac{a^{2} B_{0}}{2} )
D・ ( pi a^{2} B_{0} )
12
397State whether true or false:
A dynamo converts electric energy into mechanical energy.
A. True
B. False
12
as on
the same direction, while in 3 is in the
opposite direction. Match the following
table
Table 1 Table – 2
(a) When the current in 1 is
(p) current in 1 will increased increased i
(b) When the current in 2 is
(q) current in 2 will increase increased
(r)Current in 3 will
(c) When the current in 3 is increase
increased
( A cdot a-r ; b-r ; c-p, q )
B. ( a-p ; b-p ; c-q )
( mathrm{C} cdot mathrm{a}-mathrm{q} ; mathrm{b}-mathrm{q} ; mathrm{c}-mathrm{r} )
D. ( a-r ; b-q ; c-p )
12
399toppr
insulated from each other. The entire
loop lies in the plane (of the paper). A
uniform magnetic field ( B ) point into the
plane of the paper. At ( t=0, ) the loop
diameter as axis with a constant
angular velocity ( omega ) in the magnetic field Which of the following options is/are
correct?
This question has multiple correct options
A. The amplitude of the maximum net ( e m f ) induced due to both the loops is equal to the amplitude of maximum ( e m f ) induced in the smaller loop alone
B. The rate of change of the flux is maximum when the plane of the loops is perpendicular to plane of the paper
c. The ( e m f ) induced in the loop is proportional to the surn of the areas of the two loops
D. The net ( e m f ) induced due to both the loops is proportional to cos ( omega t )
12
400A conductor ( A B ) of length ( l ) moves in ( x-y ) plane with velocity ( overrightarrow{boldsymbol{v}}=boldsymbol{v}_{0}(hat{boldsymbol{i}}-hat{boldsymbol{j}}) cdot boldsymbol{A} )
magnetic field ( vec{B}=B_{0}(hat{i}+hat{j}) ) exists in the region. The induced emf is
A . zero
в. ( 2 B_{0} ) lv ( _{0} ),
c. ( B_{0} l v_{0} )
D. ( sqrt{2} B_{0} l v_{0} )
12
401Principle behind electric generator is
A. when a straight conductor is moved in the electric field, then current is induced in the conductor
B. when a circular loop is moved in electric field, then current is induced in the conductor.
C. when a straight conductor is moved in a magnetic field, the current is induced in the conductor.
D. none
12
402A helicopter rises vertically with a speed of ( 100 mathrm{m} / mathrm{s} ). If helicopter has length ( 10 mathrm{m} ) and horizontal component
of earth’s magnetic field is ( 5 times )
( 10^{-3} W b / m^{2}, ) then the induced emf
between the tip of nose and tail of helicopter is:
A. ( 50 v )
B. 0.5 ( v )
( c cdot 5 v )
D. 25 V
12
403State Lenz’s law.12
404A coil of insulating wire is connected to battery. If it is moved towards a galvanometer then its point gets
deflected because
A. the coil behaves like a magnettet
B. induced current is produced in the coil
C. the number of turns in the galvanometer coil remains constant
D. none of the above
12
405A small straight condctor PQ is lying at right angles to an infinite current
carrying conductor ( X Y ). If the conductor PQ is displaced on metallic rails parallel to the conductor ( X Y ), then the
direction of induced emf in PQ will be:
A. from Q to P
B. from P to Q
c. vertically downwards
D. vertically upwards
12
406The mutual inductance ( M_{12} ) of a coil 1
with respect to coil 2
A. increases when they are brought nearer
B. depends on the current passing through the coilss
c. increases when one of them is rotated about an axis
D. both (a) and
(b) are correct
12
407Find the average of the squares of emf induced over a long period.12
408An e.m.f. of 5 volt is produced by a self inductance, when the current changes at a steady rate from 3 A to 2 A in 1 millisecond. The value of self
inductance is
A . zero
в. 5 н
c. 5000 н
D. 5 mH
12
409rectangular conductor ( L M N O ) is placed in a uniform magnetic field of ( 0.5 T . ) The field is directed
perpendicular to the plane of the conductor. When the arm ( M N ) of length ( 20 mathrm{cm} ) is moved towards left with
velocity of ( 10 m s^{-1} ) calculate the emf
induced in the arm. Given the
resistance of the arm to be ( 5 Omega ) assuming that other arms are of regligible resistance) find the value of
the current in the arm
( left.begin{array}{l}mathbf{X}_{mathrm{L}} mathbf{X}^{overrightarrow{mathbf{B}}} mathbf{X} & mathbf{X} times mathbf{X} \ mathbf{X} \ mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} \ mathbf{X} & mathbf{X} & mathbf{X} & mathbf{X} \ mathbf{X}^{mathbf{o}} & mathbf{X} & mathbf{X} & mathbf{X}end{array}right] underset{mathbf{X}}{mathbf{X}}_{mathbf{X}} mathbf{X}_{mathbf{X}} mathbf{X}_{mathbf{X}} mathbf{X} )
12
410A current carrying wire produces a magnetic field in its surrounding space. The S.I. unit of magnetic flux density is
A . Henry
B. Tesla
c. ( A M^{2} )
D. A-m
12
411In the process of electromagnetic induction, the magnitude of the induced emf depends on:
Select the correct options from the following This question has multiple correct options
A. The number of turns of the coil
B. The magnetic flux linked with the coil
c. The rate of change of magnetic flux linked with the coi
D. Area of the coil
12
412A current ( I ) ampere flows along an infinitely long straight thin walked tube, then the magnetic induction at any point inside the tube is
A . infinite
B. zero
c. ( frac{mu_{0}}{4 pi} frac{2 i}{r} ) tesla
D ( frac{2 i}{r} ) tesla
12
413Give any two applications of Faraday’s law of Induction in daily life.12
414The magnetic field in a region is given by ( vec{B}=B_{0}left(1+frac{x}{a}right) hat{k} . ) A square loop of edge length ( d ) is placed with its edge
along the ( x ) – and ( y ) -axes. The loop is
moved with a constant velocity ( overrightarrow{boldsymbol{v}}=boldsymbol{v}_{mathbf{0}} hat{boldsymbol{i}} )
The emf induced in the loop is
A ( cdot frac{v_{0} B_{0} d^{2}}{a} )
B. ( frac{v_{0} B_{0} d^{3}}{a^{2}} )
( mathbf{c} cdot v_{0} B_{0} d )
( mathbf{D} cdot 2 v_{0} B_{0} d )
E . zero
12
415A circular loop of radius ( 2 mathrm{cm} ), is placed in a time varying magnetic field with rate of ( 2 T / )sec. Then induced electric
field in this loop will be:
( mathbf{A} cdot mathbf{0} )
в. ( 0.002 mathrm{V} / mathrm{m} )
c. ( 0.01 V / m )
D. ( 2 V / m )
12
416A metal conductor of length 1 m rotates
vertically about one of its ends at angular velocity 5 radians per second. If
the horizontal component of earths
magnetic field is ( 0.2 times 10^{-4} T, ) then the
e.m.f. developed between the two ends of
the conductor is
A. depends on the nature of the metal used
B. depends on the intensity of the radiation
c. depends both on the intensity of the radiation and the metal used
D. is the same for all metal and independent of the intensity of the radiation.
12
417Two spherical bobs, one metallic and
the other of glass, of the same size are allowed to fall freely from the same height above the ground. Which of the two would reach earlier and why?
12
418Define the unit of self inductance.12
419For what angle ( theta ) does the induced emf
have the largest amplitude?
12
420A wire loop is rotated in a uniform
magnetic field about an axis perpendicular to the field. The direction
of the current induced in the loop
reverse once each
A . quarter revolution
B. half revolution
c. full revolution
D. two revolution
12
uniformly distributed over its
circumference is hanging by a
insulated thread with the help of a
small smooth ring (not rigidly fixed with bigger ring). A time varying magnetic
field ( B=B_{0} sin omega t ) is switched on at ( t )
( =0 ) and the ring is released at the
same time.The average magnetic
moment of Ring in time interval 0 to
is
A ( cdot frac{B_{0} q^{2} R^{2}}{2 pi m} )
B. ( frac{B_{0} q^{2} R^{2}}{4 pi m} )
c. ( frac{B_{0} q^{2} R^{2}}{pi m} )
D. zer
12
422Stepping up of voltage by a factor of 100, reduce the current by a factor of
A . 10
B. 100
c. leaves the current unchanged
D. increase the current by a factor of 100
12
423Two identical conducting rings ( A ) and ( B )
of radius ( R ) are rolling over a horizontal
conducting plane with same speed ( v ) but in opposite direction. A constant magnetic field ( B ) is present pointing
into the plane of the paper. Then the
potential difference between the highest points of the two rings is
( A )
в. ( 2 B v R )
c. ( 4 B v R )
D. none of these
12
424The voltage applied to a purely inductive coil of self inductance
( 15.9 m H ) is given by the equation ( V= )
( 100 sin 314 t+75 sin 942 t+ )
( 450 sin 1570 t )
Find the equation of current wave.
12
425What is to be used to convert an AC
generator into DC generator?
A. split-ring type commutator must be used
B. slip rings and brushes must be used
C. a stronger magnetic field has to be used
D. a rectangular wire loop has to be used
12
426The current in the resistance ( R ) as a
function of time.
12
427
X
X
x
X
X
x
X
x
X
X
x
|| X
X
xxx xxxx
X
x
23. A conductor of length I and mass m x
can slide without any friction along
the two vertical conductors connected
at the top through a capacitor (figure).
A uniform magnetic field B is set up 1
to the plane of
12
428An electric generator converts mechanical energy into
energy.
12
429A coil has 200 turns and area of ( 70 mathrm{cm}^{2} )
The magnetic field perpendicular to the plane of the coil is ( 0.3 W b / m^{2} ) and take
( 0.1 sec ) to rotate through ( 180^{circ} . ) The value of the induced e.m.f. will be
A. ( 8.4 mathrm{v} )
B. 84
c. 42 v
D. 4.2 v
12
430The induction coil works on the
principle of
A. Self-induction
B. Mutual induction
c. Ampere’s rule
D. Fleming’s right hand rule
12
43127. Figure shows a copper rod moving with velocity v parallel
to a long straight wire carrying current=100 A. Calculate
the induced emf in the rod, where y = 5 ms, a=1 cm,
b= 100 cm.
(a) 0.23 m V
(b) 0.46 mV
(c) 0.16 mV
(d) 0.32 mV
12
432The electric field of an electromagnetic
wave in free space is given by ( vec{E} 10 cos left(10^{7} t ! k xright) hat{j} V / m ) where ( t ) and ( x )
are in seconds and metres respectively. It can be iferred that
(i) the wavelength ( % ) is ( 188.4 mathrm{m} )
(ii) the wave number ( k ) is 0.33 rad/m
(iii) the wave amplitude is ( 10 mathrm{V} / mathrm{m} )
(iv) the wave is propagating along ( +x ) direction
Which one of the following pairs of
statements is correct?
A . (iii) and (iv)
B. (i) and (ii)
c. (ii) and (iii)
D. (i) and (iii)
12
433The property of a conductor which enables to induce an EMF due to change
of current in the same coil is
12
434EMF developed by generator depends
upon:
A. size of magnet
B. length of rotating wire
D. none of these
12
435A coil having 100 turns is kept in a uniform magnetic field of induction 0.5
T. If its area changes from ( 0.3 m^{2} ) to 0.1
( m^{2} ) in 10 s, then the emf induced is
( mathbf{V} )
( A cdot 2 )
B. 1
( c cdot 4 )
D.
12
436The horizontal component of earth’s magnetic field at a place is ( 3 times 10^{-4} T ) and the dip is ( tan ^{-1}left(frac{4}{3}right) cdot A ) metal rod of length ( 0.25 m ) is placed in ( N-S )
direction and is moved at a constant
speed of ( 10 mathrm{cm} s^{-1} ) towards the east
The emf induced in the rod will be
A ( .1 mu V )
B. ( 5 mu V )
c. ( 7 mu V )
D. ( 10 mu V )
12
437A uniform rod of mass ( 6 M ) and length
( 6 l ) is bent to make an equilateral
hexagon. Its mutual inductance about an axis passing through the centre of mass and perpendicular to the plane of hexagon is
( A cdot 5 m l^{2} )
В ( .6 m l^{2} )
( mathrm{c} cdot 4 m l^{2} )
( mathbf{D} cdot 12 m l^{2} )
12
438The magnitude of the induced emf in a coil of inductance ( 30 m H ) in which the
current changes from ( 6 A ) to ( 2 A ) in ( 2 s )
is:
A ( .0 .06 mathrm{V} )
в. ( 0.6 mathrm{V} )
c. ( 1.06 V )
D. ( 6 V )
12
439A closed coil with a resistance R is
placed in a magnetic field. The flux linked with the coil is ( phi ). If the magnetic
field is suddenly reversed in direction, the charge that flows through the coil will be:
A. ( frac{phi}{2 R} )
в. ( frac{phi}{R} )
c. ( _{2} frac{phi}{R} )
D. zero
12
440An electric bulb has a rated power of ( 50 W ) at ( 100 V . ) If it is used on an ( A C )
source ( 200 V, 50 H z, ) a choke has to be
used in series with it. This choke should
have an inductance of
( mathbf{A} cdot 0.01 m H )
в. ( 1 m H )
( c .0 .1 H )
D. ( 1.1 H )
12
441A conductor is moving with the velocity v in the magnetic field and induced current is I. If the velocity of conductor becomes double, the induced
current will be
A. ( 0.5 I )
B. 1.5 ( I )
( c cdot 2 I )
D. 2.5 I
12
442What is the magnetomotive force ( (m m f) ) of a wire with 8 turns carrying three amperes of current?
A. 2,400 At
B. 240 At
( c cdot 24 mathrm{At} )
D. 2.4 At
12
443The magnetic flux linked with a coil of
( N ) turns of area of cross-section ( A ) held
with its plane parallel to the field ( B ) is
A. ( frac{N A B}{2} )
в. ( N A B )
c. ( frac{N A B}{4} )
D. 0
E . ( 2 N A B )
12
444состолор
12. A square coil ACDE with its plane vertical is released
from rest in a horizontal
uniform magnetic field B of
length 2L (figure). The X X X XE
acceleration of the coil is
(a) less than e for all the time 22 X X X X
till the loop crosses the X X X X
magnetic field completely
(b) less than g when it enters
the field and greater than g when it comes out of the
field
(c) g all the time
(d) less than g when it enters and comes out of the field
but equal to g when it is within the field
12
445Current in a circuit falls from ( 5.0 A ) to
( 0.0 A ) in 0.1 sec. If an average emf of
( 200 V ) is induced, give an estimate of the self-inductance of the circuit.
12
446Which of the following does not have the same dimensions as the Henry?
A. ( frac{text { joule }}{(text { ampere })^{2}} )
B. ( frac{text { tesla }-m^{2}}{(text { ampere })^{2}} )
c. ohm-second
D. ( frac{1}{text { Farad-second }} )
12
447(a) A rod of length ( l ) is moved
horizontally with a uniform velocity’ ( v ) ‘ in a direction perpendicular to its length through a region in which a uniform magnetic field is acting vertically downward. Derive the expression for the emf induced across the ends of the rod.
(b) How does one understand this
motional emf by invoking the Lorentz force acting on the free charge carriers
of the conductor? Explain.
12
448A square loop of side ( 20 mathrm{cm} ) is initially
kept ( 30 mathrm{cm} ) away from a region of uniform magnetic filed of ( 0.1 mathrm{T} ) as shown
in the figure. It is then moved towards
the right with a velocity of ( 10 mathrm{cm} mathrm{s}^{-1} ) till
it goes out of the field. plot a graph
showing the variation of
(i) magnetic flux ( (phi) ) through the loop
with time(t).
(ii) induced emf ( (varepsilon) ) in the loop with
time t.
(iii) induced current in the loop, if it has
resistance of ( 0.1 Omega )
12
449An alternating potential ( V=V_{0} sin omega t )
is applied across a circuit. As a result, the current ( boldsymbol{I}=boldsymbol{I}_{0} sin left(boldsymbol{omega} boldsymbol{t}-frac{boldsymbol{pi}}{2}right) ) flows
in it. The power consumed in the circuit per cycle is:
A . zero
в. ( 0.5 I_{0} V_{0} )
с. ( 0.707 I_{0} V_{0} )
D. ( 1.414 I_{0} V_{0} )
12
450To measure the field ( B ) between the
poles of an electromagnet, a small test loop of area ( 1 mathrm{cm}^{2} ), resistance ( 10 Omega ) and 20 turns is pulled out of it. A galvanometer shows that a total charge of ( 2 mu C ) passed through the loop. The
value of ( B ) is
A . ( 0.001 T )
в. ( 0.01 T )
( c .0 .17 )
D. ( 1.0 T )
12
451The normal drawn to the surface of a
conductor makes an angle ( theta ) with the direction of field ( vec{B}, ) the flux ( phi ) passing through the area ( vec{A} ) is given by
A. ( phi=A B sin theta )
в. ( _{phi}=frac{B}{A} )
c. ( phi=B A )
D. ( phi=B A cos theta )
12
452Which of the following best describe the electromagnetic induction?
A. the ability of a changing magnetic field to induce a voltage in a conductor
B. the ability of a conductor to generate a magnetic field
C. the ability of a static magnetic field to induce a voltage in a conductor
D. the ability of a permanent magnet to induce a voltage in a coil
E. the ability of a conductor to induce a magnetic field
12
453A conducting circular loop is placed in a uniform magnetic field ( B=0.020 T )
with its plane perpendicular to the field. Somehow, the radius of the loop starts
shrinking at a constant rate of ( 1 mathrm{mm} / mathrm{s} ) Find the induced current in the loop at
an instant when the radius is ( 2 mathrm{cm} )
12
454Reactance of a coil is ( 157 Omega ). On
connecting the coil across a source of frequency ( 100 H z ), the current lags
behind e.m.f. by ( 45^{circ} . ) The inductance of
the coil is
A ( .0 .25 H )
в. ( 0.5 H )
( c .4 H )
D. ( 314 H )
12
455The wire is found to vibrate in the third
harmonic. The maximum emf induced
is
( A )
B.
[
frac{3(A B) omega}{k}
]
( c )
[
frac{2(A B) omega}{k}
]
( D )
[
frac{(A B) omega}{k}
]
12
456Assertion
An electric field ( vec{E} ) is induced in a
closed loop where magnetic flux is varied.The induced ( overrightarrow{boldsymbol{E}} ) is not a
conservative field
Reason The line integral ( vec{E} . overrightarrow{d l} ) around the closed loop is nonzero
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
457The magnitude of the force required to
move the conducting rod at constant
speed ( 5 c m / s ) at the same instant ( t= )
( 2 s, ) is equal to
B. ( 0.12 N )
c. ( 0.08 N )
D. ( 0.64 N )
12
458Check the incorrect statement: When a
magnet is moved into a coil the
strength of the current depends on:
A. The number of turns in the coil
B. The speed with which the magnet moves
c. The resistance of the coil
D. None of the above
12
459The figure shows a square loop ( L ) of side
( 5 c m ) which is connected to a network of
resistances. The whole setup is moving
towards right with a constant speed of
( 1 mathrm{cm} s^{-1} . ) At some instant, a part of Lis
in a uniform magnetic field of ( 1 T )
perpendicular to the plane of the loop. If
the resistance of ( L ) is ( 1.7 Omega ), the current
in the loop at that instant will be close
to
A . ( 115 mu A )
в. 170 иА
( c cdot 60 mu A )
D. ( 150 mu A )
12
460Consider the situation shown. The wire
AB is sliding on fixed rails with a constant velocity. If the wire ( A B ) is replaced by semi-circular wire, the magnitude of induced e.m.f will
A. increase
B. decrease
c. remain the same
D. increase or decrease depending on whether the semicircle buldges towards the resistance or away from it
12
461Find the maximum emf induced12
462The self inductance of two solenoids ( A )
( & mathrm{B} ) having equal length are same. If the number of turns in two solenoids ( A & B )
are 100 and 200 respectively. The ratio
of radii of their cross-section will be
A . 2: 1
B. 1: 2
c. 1: 4
D. 4: 1
12
463An electron moves on a straight line
path ( Y Y^{prime} ) as shown in figure. A coil is
kept in the right such that ( Y Y^{prime} ) is in the
plane of the coil. At the instant when the
electron gets closest to the coil (neglect self-induction of the coil),
A. the current in the coil flows clockwise
B. the current in the coil flows anticlockwise
c. the current in the coil is zero
D. the current in the coil does not change the direction as the electron crosses point ( O )
12
464along a diameter of a conducting ring of
radius ( 0.1 m ) and lies on ( x ) -y plane. There
is a magnetic field ( vec{B}=(50 T) hat{K} . ) The
ring rotates with an angular velocity
( omega=20 r a d s^{-1} ) about its axis. An
external resistance of ( 10 Omega ) is connected
across the center of the ring and rim.
The current through external resistance
is:
( mathbf{A} cdot frac{1}{4} )
B. ( frac{1}{2} )
( c cdot frac{1}{3} )
D. zero
12
465A thin semicircular conducting the ring
( (P Q R) ) of radius ( ^{prime} r^{prime} ) is falling with its
plane vertical in a horizontal magnetic
field ( B ), as shown in figure. The potentia difference developed across the ring
when its speed is ( v ), is
A. Zero
B. ( B v pi r^{2} / 2 ) and ( P ) is at higher potential
( mathrm{c} . pi r B v ) and ( R ) is at higher potential
D. ( 2 r B v ) and ( R ) is at higher potential
12
466The direction of torque produced due to
induced current is
A . counter-clockwise
B. clockwise
C. lateral to produce precession
D. none of these
12
467A train is moving from south to north with a velocity of ( 90 mathrm{km} / mathrm{h} ). The vertical component of earth’s
magnetic induction is ( 0.4 times ) ( 10^{-4} W b / m^{2} . ) If the distance between
the two rails is ( 1 m, ) what is the induced
e.m.f. in its axle?
A. ( 1 m V )
B. ( 0.1 m V )
( mathrm{c} .10 mathrm{mV} )
D. ( 100 m V )
12
468On making a coil of copper wire of length I and coil radius ( r, ) the value of self inductance is obtained as ( L ). If the
coil of same wire, but of coil radius r/2, is made, the value’ of self inductance will be- –
A . 2L
B. 4L
( c cdot L / 2 )
( D cdot L / 3 )
12
469Write an expression of magnetic flux density ‘B’ at a point in end-on position or an axial position of a magnetic dipole. (Derivation not required.)12
470Energy in a current carrying coil is stored in the form of
A . electric field
B. magnetic field
c. dielectric strength
D. heat
12
471( A, B ) and ( C ) are the three coils of
conductor having different number of
turns, wound around a soft iron ring as
shown in the figure. Ends of coils ( B ) and
( C ) are connected to the galvanometers.
The observation that can be made when
ends of coil ( A ) are connected to an A.C.
source is
A. Same electric current is induced in ( B ) and ( C )
B. No electric current is induced in ( B ) and ( C )
c. Induced electric current is more in ( B ) than in ( C )
D. Induced electric current is less in ( B ) than in ( C )
12
472a) Redraw the above diagram.
b) This diagram represents
c) Label the parts of the diagram
d) Mention the working principle of the
device denoted by this diagram.
12
473The magnetic field ( B=2 t^{2}+4 t^{2} )
(where ( t= ) time ) is applied perpendicular to the plane of a circular wire of radius ( r ) and resistance ( R ). If all
the units are in SI the electric charge that flows through the circular wire during ( t=0 s ) to ( t=2 s ) is
A ( cdot frac{6 pi r^{2}}{R} )
в. ( frac{24 pi r^{2}}{R} )
c. ( frac{32 pi r^{2}}{R} )
D. ( frac{48 pi r^{2}}{R} )
12
474Dynamo converts:
A. electric energy into magnetic energy
B. magnetic energy into potential energy
C. mechanical energy into electrical energy
D. no energy
12
475A conducting loop of radius ( R ) is has a
( B ) -field directed through it at a
downward angle as shown. Determine
the amount of flux in the loop.
( mathbf{A} )
( B )
( mathbf{c} cdot B pi R^{2} sin theta )
( mathbf{D} cdot B pi R^{2} cos theta )
12
476A material of ( 0.25 mathrm{cm}^{2} ) cross sectional
area is placed in a magnetic field of strength ( (H) 1000 A m^{-1} . ) Then the
magnetic flux produced is:
[Susceptibility of material is 314 and
Permeability of free space, ( mu_{0}=4 pi times )
( 10^{-7} H m^{-1} )
A . ( 8.33 times 10^{-8} mathrm{Wb} )
В. ( 1.84 times 10^{-6} mathrm{Wb} )
( mathbf{c} cdot 9.87 times 10^{-6} mathrm{Wb} )
D. ( 3.16 times 10^{-8} mathrm{Wb} )
12
477A solenoid is connected to a source of
constant e.m.f. for a long time. A soft iron piece is inserted into it. Then, which of the following is/are correct? This question has multiple correct options
A. Self-inductance of the solenoid gets increased
B. Flux linked with the solenoid increases; hence, steady state current gets decreased
C. Energy stored in the solenoid gets increased
D. Magnetic moment of the solenoid gets increased
12
478Self inductance ( L ) of long solenoid is
being proportional to the number of
turns ( N ) as-
A . ( N )
В. ( N^{2} )
c. ( N^{3} )
D. ( N^{4} )
12
479Which of the following can’t increase
the voltage produced by the generator?
A. Using a powerful electromagnet to make the magnetic field stronger in place of a permanent magnet.
B. By winding the coil round a soft iron core to increase the strength of magnetic field.
C. By using a coil with more turns.
D. Changing the material of the coil.
12
480The Sl unit of magnetic field induction
is
A. Tesla
B. weber
c. weber/m
D. weber. m
12
481In the given figure current from ( A ) to ( B ) in
the straight wire is decreasing.

The direction of induced current in the
loop is
A . clockwise
B. anticlockwise
c. changing
D. nothing can be said

12
482An ac generator consists of a coil of 200 turns, ( 100 mathrm{cm} ) in diameter. If the coil
rotates at 500 rpm in a magnetic field of ( 0.25 mathrm{T} ), then the maximum induced
emf
A . 20.6 ( v )
B. 51.7
c. 4.1
D. None of the above
12
483The value of magnetic field induction which is uniform is 2 T. What is the
flux passing through a surface of area ( 1.5 m^{2} ) perpendicular to the field?
12
4844. When the current changes from +2 A to -2 A in 0.05 s,
an emf of 8 V is induced in a coil. The coefficient of self-
induction of the coil is
(a) 0.1 H
(b) 0.2 H
(c) 0.4 H
(d) 0.8 H (AIEEE 2003)
12
485Derive an expression for the force on current carrying in a magnetic field.12
486The figure shows a small circular coil of area A suspended from a point 0 by a string of length I in a uniform magnetic induction B in the horizontal direction. If
the coil is set into oscillations likes
simple pendulum by displacing it a
small angle ( theta_{0} ) as shown, find emf induced in the coil as a function of time.
Assume the plane of the coil is always in the plane of string.
12
487Assertion (A) : The net magnetic flux coming out of a closed surface is always zero. Reason
(R) : Unlike poles of equa strength exist together
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
c. A is true, But R is false
D. A is false, But R is true
12
488The value of coefficient of mutual
induction for the arrangement of two coils shown in the figure will be :
A. zero
B. Maximum
c. Negative
D. Positive
12
489Give a few applications of Faradays law of induction in daily life.12
490What is electromagnetic induction?12
491Explain the work of an Electric
Generator with diagram.
12
492The number of turns in the coil of an ( A C )
generator ar e100 and its cross-
sectional area is ( 2.5 m^{2} . ) The coil is
revolving in a uniform magnetic field of strength ( 0.3 T ) with the uniform angular velocity of 60 rad/s. The value of maximum value produced is ( mathbf{k V} )
A . 1.25
в. 4.50
c. 6.75
D. 2.25
12
493Magnetic flux has the dimension
( mathbf{A} cdot M L^{2} A^{-2} )
B ( cdot M L^{2} T^{-2} A^{-1} )
( mathbf{C} cdot M T^{-2} A^{-1} )
D. ( M L^{2} T^{-2} A^{-2} )
12
494When the flux linked with a coil
changes:
A. current is always induced
B. an emf and a current are always induced
c. an emf is induced but a current is never induced
D. an emf is always induced and a current is induced when the coil is a closed one
12
495Two rail tracks are ( 1 m ) apart and insulated from each other and
insulated from ground. A milli-voltmeter is connected across the rail-tracks.
When a train travelling at ( 180 mathrm{km} / mathrm{h} )
passes through what will be the reading in milli-voltmeter? Given : horizontal
component of earth’s field ( sqrt{3} times 10^{-4} T )
and dip at the place ( 60^{circ} )
A. ( 1.5 mathrm{mV} )
B. ( 15 mathrm{mV} )
c. ( frac{15}{sqrt{3}} m V )
D. ( frac{1.5}{sqrt{3}} m V )
12
496Two circular coils are placed adjacent
to each other. Their planes are paralle
and currents through them ( i_{1} ) and ( i_{2} ) are
in same directions. Choose the correct
options
This question has multiple correct options
A. When ( A ) is brought near ( B ), current ( i_{2} ) will decrease
B. When ( A ) is brought near ( B ), current ( i_{2} ) will increase
C. When current ( i_{1} ) is increased, current ( i_{2} ) will decrease
D. When current ( i_{1} ) is increased, current ( i_{2} ) will increase
12
497A conducting circular loop of area ( 1 mathrm{nm} ) is placed compulsary with a long, straight wire at a distance of current
which changes from 10 A to zero in 0.1
s. Find the average emf induced in the
loop in 0.1 s.
12
498A square metal wire loop of side ( 10 mathrm{cm} )
and of resistance ( 2 Omega ) moves with
constant velocity in the presence of a uniform magnetic field of induction ( 4 mathrm{T} )
perpendicular and into the plane of the loop. The loop is connected to a network
of resistance as shown in the Figure. If
the loop should have a steady current of ( 2 mathrm{mA} ), the speed of the loop must be (in ( left.mathrm{cm} mathrm{s}^{-1}right): )
4
B.
( c )
)
12
499A copper rod of length ( l ) is rotated about one end, perpendicular to the uniform
magnetic field ( B ) with constant angular velocity ( omega . ) The induced emf between
two ends of the rod is:
A ( cdot frac{1}{2} B omega l^{2} )
в. ( B omega l^{2} )
c. ( frac{3}{2} B omega l^{2} )
D . ( 2 B omega l^{2} )
12
500A dynamo is used to supply electric current to a small electric bulb, If the
number of turns in the coil of
this dynamo is doubled, then the voltage in the bulb.
A. will decrease
B. Remains unchanged
c. will be doubled
D. Will increase by a factor between 1 and 2
12
501A conducting rod ( mathrm{AB} ) moves parallel to
X-axis in a uniform magnetic field,
pointing in the positive X-direction. The
end ( A ) of the rod gets
A. positively charged
B. negatively charged
c. neutral
D. first positively charged and then negatively charged
12
502The working of magnetic braking of trains is based on
B. Eddy current
c. Alternating current
D. Pulsating current
12
503A closely wound flat circular coil of 25
turns of wire has diameter of ( 5 mathrm{cm} )
which carries current of 4 amperes, the flux density at the centre of a coil will be
A ( cdot 1.256 times 10^{-3} ) tesla
В. ( 1.679 times 10^{-5} ) tesla
c. ( 1.512 times 10^{-5} ) telsa
D. ( 2.28 times 10^{-4} ) telsa
12
504A square conducting coil of area ( = )
( 100 mathrm{cm}^{2} ) is placed normally inside a
uniform magnetic field of ( 10^{3} W b m^{-2} ) The magnetic flux linked with the coil is
Wh.
A . 10
B . ( 10^{-5} )
( c cdot 10^{5} )
D. 0
12
505For a coil having ( boldsymbol{L}=2 boldsymbol{m} boldsymbol{H}, ) current
flow through it is ( I=t^{2} e^{-t} ) then the time
at which emf become zero: –
( mathbf{A} cdot 2 s )
B . ( 1 s )
c. ( 4 s )
D. ( 3 s )
12
506The induced emf developed across the
rod must be
A. ( 4.5 mathrm{V} ) with b at higher potential
B. 1.5 V with a at higher potential
c. 1.5 V with b at higher potential
D. 4.5 V with a at higher potential
12
507Two coils, ( A ) and ( B ), are lined such that
emf ( epsilon ) is induced in ( B ) when the current
in ( A ) is changing at the rate ( I ). If ( i ) current
is now made to flow in ( mathrm{B} ), the flux linked
with ( A ) will be :
A. ( (epsilon / I) i )
i
B. ( epsilon i I )
c. ( (epsilon I) )
D. ( i I / epsilon )
12
508A metallic rod of length ( l^{prime} ) is tied to a
string of length ( 2 l ) and made to rotate
with angular speed ( omega ) on a horizontal table with one end of the string fixed. If
there is a vertical magnetic field ( B^{prime} ) in the region, the e.m.f. induced across the
ends of the rod is:
A ( cdot frac{3 B omega l^{2}}{2} )
в. ( frac{4 B omega l^{2}}{2} )
c. ( frac{5 B omega l^{2}}{2} )
D. ( frac{2 B omega l^{2}}{2} )
12
509An a.c. generator consists of a coil of
10,000 turns and of area ( 100 mathrm{cm}^{2} . ) The
coil rotates at an angular speed of 140 rpm in a uniform magnetic field of
( 3.6 times 10^{-2} mathrm{T} . ) Find the maximum value
of the emf induced.
12
510toppr ( t )
emf induced with time
( s )
12
511A horizontal straight conductor when placed along south-north direction falls under gravity; there is
A. an induced current from south-to-north direction
B. an induced emf current from north-to-south direction
c. no induced emf along the length of the conductor
D. an induced emf along the length of the conducto
12
512( A B C ) is an equilateral triangle with ( O ) as its centre, ( vec{F}_{1}, vec{F}_{2} ) and ( vec{F}_{3} ) represent three forces acting along the sides ( A B, B C ) and ( A C ) respectively. If the
total torque about ( O ) is zero then the
magnitude of ( vec{F}_{3} ) is?
A ( frac{F_{1}+F_{2}}{2} )
( mathbf{B} cdot 2left(F_{1}+F_{2}right) )
( c cdot F_{1}+F_{2} )
D. ( F_{1}-F_{2} )
12
513If the resistances of values ( R_{1} ) and ( R_{2} )
are connected on both ends as shown in
figure, current ( I, ) flowing through
resistance ( R_{1} ) is given by
( A )
[
frac{B l R_{2}left(v_{1} r_{2}-v_{2} r_{1}right)}{R_{1} R_{2}left(r_{1}+r_{2}right)+r_{2} r_{1}left(R_{1}+R_{2}right)}
]
B.
[
frac{B l R_{2}left(v_{1} r_{2}+v_{2} r_{1}right)}{R_{1} R_{2}left(r_{1}+r_{2}right)+r_{2} r_{1}left(R_{1}+R_{2}right)}
]
( c )
[
frac{B l R_{2}left(v_{1} r_{2}-v_{2} r_{1}right)}{R_{1} R_{2}left(r_{1}-r_{2}right)+r_{2} r_{1}left(R_{1}+R_{2}right)}
]
D.
[
frac{B l R_{2}left(v_{1} r_{2}-v_{2} r_{1}right)}{R_{1} R_{2}left(r_{1}+r_{2}right)-r_{2} r_{1}left(R_{1}+R_{2}right)}
]
E . nont
12
514Explain Faradays law of induction with the help of activity.12
51542. A wire of fixed length is wound in such a way that it forms
a solenoid of length ‘l’ and radius ‘r’. Its self-inductance is
found to be L. Now if same wire is wound in such a way
that it forms a solenoid of length 1/2 and radius r/2, then
the self-inductance will be
(a) 2L
(b) L
(c) 4L
(d) 8 L
12
516Describe the coil and magnet experiment to demonstrate electromagnetic induction.12
517A lossless coaxial cable has a
capacitance of ( 7 times 10^{-11} mathrm{F} ) and an
inductance of ( 0.39 mu H . ) Calculate
characteristic impedance of the cable.
A . 65
B. 75
( c cdot 66 )
D. 77
12
518A straight conductor ( 0.1 mathrm{m} ) long moves in a uniform magnetic field 0.1 T. The velocity of the conductor is ( 15 mathrm{m} / mathrm{s} ) and is directed perpendicular to the field. The emf induced between the two ends
of the conductor is:
A . ( 0.10 mathrm{v} )
B. 0.15 ( v )
c. ( 1.50 v )
D. 15.00
12
519Two coils are placed close to each other. The mutual inductance of the pair of
coils depend upon:
A. the currents in the two coils
B. the rates at which currents are changing in the two coils
c. relative position and orientation of the two coils
D. the materials of the wires of the coil
12
520Two coils ( X ) and ( Y ) are placed in a
circuit such that a current changes by
( 3 A ) in coil ( X ) and magnetic flux changes of ( 1.2 ~ W b ) occurs in ( Y ). The
value of mutual inductance of the coils
is :
( mathbf{A} cdot 0.2 H )
в. ( 0.4 mathrm{H} )
c. ( 0.6 H )
D. ( 3.6 H )
12
521A straight coaxial cable of negligible active resistance is receiving energy
from a constant voltage source ( V ) Current consumed is ( I ). Find the energy
flux across the cross-section. Assume
conductive sheath to be thin.
12
522When the number of turns per unit length in a solenoid is doubled then its
coefficient of self induction will become
A . half
B. double
c. four times
D. unchanged
12
523Who gave the principle of Electromagnetic Induction?
A. Volta
B. Ampere
D. orested
12
524A square loop of side a is rotating about
its diagonal with angular velocity ( omega ) in
perpendicular magnetic field ( overline{boldsymbol{B}}, ) figure It has 10 turns. The e.m.f. induced is?
A. ( B a^{2} ) sinwt
B. ( B a^{2} )coswt
D. ( 10 B a^{2} omega ) sinw
12
525Which of following can induce the maximum induced voltage?
A. 1 amp dc.
B. 1 amp 1 Н ( z ).
c. 1 amp 100 н ( z )
D. 20 amp dc.
12
526Discuss with theory the method of inducing emf in a coil by changing its orientation with respect to the direction of the magnetic field.12
527A semi-circular conducting ring acb of radius ( R ) moves with constant speed ( v )
in a plane perpendicular to uniform
magnetic field ( B ) as shown in figure. Identify the correct statement
A ( cdot V_{a}-V_{c}=B R v )
В. ( V_{b}-V_{c}=B R v )
c. ( V_{a}-V_{b}=0 )
D. None of these
12
528The area of a coil is ( 500 c m^{2} ) and the
number of turns in it is ( 2000 . ) It is kept
perpendicular to a magnetic field of induction ( 4 times 10^{-5} W b / m^{2} . ) The coil is
rotated through 180 in 0.1 second. If
the resistance of the total circuit is ( 20 Omega )
then the value of the induced charge
flowing in the circuit will be :
A ( cdot 1 times 10^{-4} C )
В. ( 2 times 10^{-4} mathrm{C} )
c. ( 3 times 10^{-4} C )
D. ( 4 times 10^{-4} C )
12
529Gauss is unit of which quantity?
A. ( H )
в. ( B )
( c cdot phi )
D. ( I )
12
530The magnetic field inside a ( 2 m H )
inductor becomes 0.8 of its maximum
value in ( 20 mu s ) when the inductor is
joined to battery. Find resistance of the circuit.
A . ( 160 Omega )
B. ( 80 Omega )
( c .320 Omega )
D. ( 240 Omega )
E. none of these
12
531A metallic ring is attached to the wall of the room.When the north pole of magnet is brought near the ring, the induced current in the ring is:
A . zero
B. in clockwise direction
c. in anti-clockwise direction
D. infinite
12
532Which of the following determines the direction of magnetic field due to a current carrying conductor?
A. Faraday’s law of electromagnetic induction
B. Fleming’s left hand rule
c. Lenz’s law
D. Maxwell’s cork screw rule
12
533A rectangular loop carrying a current
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 a steady current lis established in the wire as shown in the
figure, the loop will:
A. rotate about an axis parallel to the wire
B. move away from the wire
C. remain stationary
D. move towards the wire
12
534An inductor may store energy in
A. its electric field
B. its coils
c. its magnetic field
D. both in electric and magnetic fields
12
535A coil and a magnet moves with their constant speeds ( 5 m / )sec and ( 3 m / )sec
respectively, towards each other, then induced emf in coil is ( 16 m V . ) If both
moves in the same direction, then
induced emf in the coil:
( mathbf{A} cdot 15 m V )
в. ( 4 m V )
c. ( 64 m V )
D. zero
12
536A square of side L meters lies in the ( x-y )
plane in a region where the magnetic field is given by ( overline{boldsymbol{B}}=boldsymbol{B}_{0}(mathbf{2} hat{boldsymbol{i}}+boldsymbol{3} hat{boldsymbol{j}}+ )
( 4 hat{k}) T, ) where ( B_{0} ) is constant. The magnitude of flux passing through the
square is:
( mathbf{A} cdot 8 B_{0} L^{2} W b )
B. ( 12 B_{0} L^{2} W b )
c. ( 4 B_{0} L^{2} W b )
D. ( sqrt{4 times 29} B_{0} W b )
12
537In shown fig. the circular loop of wire is
moved with velocity towards the infinite
current carrying wire. Then
A. No current is induced in loop
B. Current is induced in loop clockwise
c. Current is induced in loop anticlockwise
D. Extra charges are induced on the wire loop
12
538A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An emf is induced in the loop if
( A ). it is translated
B. it is rotated about its axis
c. it is kept untouched for several minutes
D. it is cut into two pieces
12
539A long solenoid with 20 turns per ( c m )
has a small loop of area ( 2.0 mathrm{cm}^{2} ) placed inside the solenoid normal to its axis. If
the current carried by the solenoid changes steadily from ( 2.0 A ) to ( 4.0 A ) in
( 0.1 mathrm{sec}, ) calculate the induced emf in
the loop while the current is changing.
12
540Flux associated with coil of unit area
placed int he magnetic field of
induction ( B ) is doubled in ( 0.2 s . ) The emf
induced in the coil is:
A . ( 5 V )
B. ( 10 B V )
( mathrm{c} .5 B V )
D. ( 10 V )
12
541Describe the working of AC electric generator with diagram:12
542If strength of magnetic field ( bar{B}=2 hat{i}+ ) ( hat{boldsymbol{j}}-hat{boldsymbol{k}} ) and area vector is ( overline{boldsymbol{A}}=mathbf{3} hat{boldsymbol{i}}-hat{boldsymbol{j}} )
then find the magnetic flux link with
area vector
A. 4 weber
B. 6 weber
c. 7 weber
D. 5 weber
12
figure. The ring has a narrow gap f width
( delta ) in its circumference. The cross-
sectional area of the solenoid is ( a ). The
solenoid has a uniform internal field of
magnitude ( B(t)=B_{0}+beta t, ) where ( beta> )
0. Assume that no charge can flow
across the gap, the face(s) accumulating an excess of positive
charge is/are
( mathbf{A} cdot F_{1} )
B . ( F_{2} )
c. ( F_{1} ) and ( F_{2} )
D. difficult to conclude as data given are insufficient
12
544Energy in a current carrying coil is stored in the form of
A . electric field
B. magnetic field
c. dielectric strength
D. heat
12
5456. A coil having n turns and resistance R ohm is connected
with a galvanometer of resistance 4R ohm. This
combination is moved in time t second from a magnetic
field W, weber to W, weber. The induced current in the
circuit is
W2 – W
n(W2-W)
(a) –
5 Rnt
(b)-
5Rt
(c)

W2-W
Rnt
n(W2-W)
(d) –
(AIEEE 2004)
12
546A generator or dynamo works on the principle:
A. Heating effect of electric current
B. Electromagnetic induction
c. chemical effect of electric current
D. All of the above
12
547toppr
voltage with time in the coil?
( A )
B.
( c )
D.
12
548The magnitude of the earths magnetic
field at a place is ( B_{0} ) and the angle of
dip is ( delta . A ) horizontal conductor of length
lying along the magnetic north-south moves eastwards with a velocity ( v . ) The emf induced across the conductor is:
A . zero
B. ( B_{0} v l sin delta )
c. ( B_{0} l v )
D. ( B_{0} l cos delta )
12
549( mathrm{cm} ) and having a resistance of 0.2 ohm
is allowed to slide over two paralle
thick metallic rails with uniform
velocity of ( 0.2 mathrm{m} / mathrm{s} ) as shown in the
figure. The rails are situated in a
horizontal plane. If the horizontal
component of earth’s magnetic field is
( 0.3 times 10^{-4} mathrm{T} ) and a steady state current
of ( 3 mu A ) is induced through the rod. The
angle of dip will be :
A ( cdot tan ^{-1}left(frac{3}{4}right) )
B. ( tan ^{-1}left(frac{1}{sqrt{3}}right) )
( mathbf{c} cdot tan ^{-1}(sqrt{3}) )
D ( tan ^{-1}left(frac{1}{3}right) )
12
550A rectangular loop of sides ( a ) and ( b ) is
placed in ( boldsymbol{x}-boldsymbol{y} ) plane. A uniform but
time varying magnetic field of strength ( vec{B}=20 t hat{i}+10 t^{2} hat{j}+50 hat{k} ) is present in
the region. The magnitude of induced
emf in the loop at time ( t ) is :
A. ( 20+20 t )
B . 20
( c .20 t )
D. zero
12
551A uniform circular loop of radius ( a ) and resistance ( R ) is placed perpendicular to
a uniform magnetic field ( B ). One half of
the loop is rotated about the diameter
with angular velocity ( omega ) as shown in
figure. Then, the current in the loop is:
This question has multiple correct options
A. zero, when ( theta ) is zer
B. ( frac{pi a^{2} B omega}{2 R}, ) when ( theta ) is zero
c. zero, when ( theta=pi / 2 )
( stackrel{pi a^{2} B omega}{2 R}, ) when ( theta=frac{pi}{2} )
12
552If a loop in a basic dc generator suddenly begins rotating at a faster speed, the induced voltage
A. remains unchanged
B. reverses polarity
c. increases
D. decreases
12
553If the speed of rotation of armature coil is increased in an AC generator
A. Magnitude of current increases
B. Frequency of current increases
c. Both 1 and 2
D. Magnitude of current increases, frequency decreases
12
554When the magnetic flux associated with a coil changes an emf is induced in the circuit. State Faraday’s law of electromagnetic induction.12
555(c) Vo-Vp = 8 V (U P
21. A wire is sliding as shown in figure. The angle between
the acceleration and the velocity of the wire is
30°
Tes
(a) 30°
(c) 120°
(b) 40°
(d) 90°
liding onductor of length lis
ed
12
556A conducting ring of radius ( r ) is rolling without slipping with a constant angular velocity ( omega ) (figure). If the
magnetic field strength is ( B ) and is directed into the page then the emf induced across ( P Q ) is
A. ( B omega r^{2} )
в. ( frac{B omega}{2} )
c. ( 4 B omega r^{2} )
D. ( frac{B omega}{4} )
12
557The coefficient of self induction of a coil
is given by
( ^{text {A }} cdot L=left(-frac{d I}{d t}right) )
B. ( L=-frac{e d I}{d t} )
c. ( _{L}=frac{d I}{e d t} )
D. ( L=frac{d I}{d t} e^{2} )
12
558Two circular conducting loops of radii
( R_{1} ) and ( R_{2} ) are laying concentrically in
the same plane. If ( boldsymbol{R}_{1}>boldsymbol{R}_{2} ) then the
mutual inductance (M) between them
will be proportional to:
A ( cdot frac{R_{1}}{R_{2}} )
в. ( frac{R_{2}}{R_{1}} )
c. ( frac{R_{1}}{R_{2}^{2}} )
D. ( frac{R_{2}^{2}}{R_{1}} )
12
559When the plane of the rectangular coil is parallel to the direction of the magnetic field in a dynamo, then
A. Induced current will be zero
B. Induced current is maximum
c. AC is produced.
D. DC is produced.
12
560Find the emf induced as a function of
time it is zero at ( t=0 ) and is increasing
in positive direction
12
561According to Faraday’s law, the total charge induced in a conductor that is moved in a magnetic field depends up
on:
A. Initial magnetic flux
B. Final magnetic flux
c. Rate of change of magnetic flux
D. change in magnetic flux
12
562ance
к
14. An equilateral triangular loop ADC having some resistance
is pulled with a constant velocity v out of a uniform
magnetic field directed into the paper (figure). At time
1 = 0, side DC of the loop is at edge of the magnetic field
x x x x x x
x x x x x x
xxxx, x
xxxxx
xxxx
xxxxx
x
The induced current (i) versus time (t) graph will be as
(а) 11
(b)
(c) і
15 Eicure ohоua опашана Тали
12
563A coil is placed in transverse magnet
field of 0.02 T. If this coil starts
shrinking at a rate of ( 1 mathrm{mm} / mathrm{sec}, ) while
its radius remains ( 4 mathrm{cm}, ) then what is
the value of induced emf?
( A cdot 2 mu V )
B . ( 2.5 mu V )
( c .5 mu V )
D. ( 8 mu V )
12
564A rectangular coil of 300 turns has an
average area of ( 25 mathrm{cm} times 10 mathrm{cm} . ) The coil
rotates with a speed of 50 cps in uniform magnetic field of strength ( 4 times ) ( 10^{-2} T ) about an axis perpendicular to
the field. The peak value of the induced emf is ( (text { in } v o l t) )
A. ( 300 pi )
B. 3000 ( pi )
( c .3 pi )
D. ( 30 pi )
12
565In the figure shown, a T-shaped conductor moves with constant angular
velocity ( omega ) in a plane perpendicular, to uniform magnetic field ( vec{B} ). The potential
difference ( V_{A}-V_{B} ) is
A. zero
в.
[
frac{1}{2} B omega l^{2}
]
c. ( 2 B omega l^{2} )
D. Bomega ( l^{2} )
12
566The armature of a DC motor has ( 20 Omega )
resistance. It draws a current of 1.5
amp when run by ( 200 V ) DC supply. The value of back emf induced in it will be
( mathbf{A} cdot 150 V )
в. ( 170 V )
( mathbf{c} cdot 180 V )
D. ( 190 V )
12
567An electric circuit is composed of three
conducting rods ( M O, O N ) and ( P Q ) as
shown in figure. The resistance of the
rods per unit length is ( lambda ). The rod ( P Q )
slides, as shown in the figure, at a constant velocity ( v, ) keeping its tilt
angle relative to ( O N ) and ( N=M O )
fixed ( 45^{circ} . ) At each instance, the circuit
is closed. The whole system is embedded in a uniform magnetic field
( B, ) which is directed perpendicularly into the page. Compute the timedependent induced electric current induced in the rods?
12
568The loop shown moves with a velocity ( v )
in a uniform magnetic field of
magnitude ( B ), directed into the paper. The potential difference between points
( P ) and ( Q ) is ( e . ) Then
This question has multiple correct options
B. ( e=B l v )
C. ( P ) is positive with respect to ( Q )
D. ( Q ) is positive with respect to ( P )
12
569Draw a neat diagram of the following
and label the parts.
DC dynamo
12
570A conducting circular loop is placed in a uniform magnetic field, ( B=.025 ) T with its plane perpendicular to the loop The radius of the loop is made to shrink at a
constant rate of ( 1 mathrm{mms}^{-1} ). The induced
e.m.f. when the radius is ( 2 mathrm{cm} ), is
( mathbf{A} cdot 2 pi mu V )
в. ( pi mu V )
c. ( frac{pi}{2} mu V )
D. ( 2 mu V )
12
571(a) Obtain an expression for the energy stored in a solenoid of self-inductance
( L^{prime} ) when the current though it grows from zero to ( ^{prime} I^{prime} )
(b) A square loop MNOP of side ( 20 mathrm{cm} ) is placed horizontally in a uniform magnetic field acting vertically downwards as shown in the figure. The loop is pulled with a constant velocity of ( 20 mathrm{cm} s^{-1} ) till it goes out of the field
(i) Depict the direction of the induced current in the loop as it goes out of the field. For how long would the current in the loop persist?
(ii) Plot a graph showing the variation of magnetic flux and induced emf as a function of time.
[
x times x times x times x times x
]
12
572A wheel with 10 spokes each of length ‘ ( L )
( mathrm{m} ) is rotated with a uniform angular velocity ‘ ( omega ) ‘ in a plane normal to the
magnetic field ‘ ( B ) ‘. The emf induced between the axle and the rim of the
wheel.
A ( cdot frac{1}{2} N omega B L^{2} )
B. ( frac{1}{2} omega B L^{2} )
( mathrm{c} cdot omega b L^{2} )
D. ( N omega B L^{2} )
12
573Area of a long solenoid is doubled.So how many times we have to increase its
length to keep its self inductance
constant-
A.
B. 2
( c cdot 3 )
( D )
12
574yual diape
( P Q R S^{prime} ) of dimensions, ( l times l ) is placed
inside a constant and uniform Magnetic Field ( vec{B}=B_{0}left(frac{1}{sqrt{2}} hat{i}+frac{1}{sqrt{2}} hat{j}right) ) as shown
in the figure such that it’s sides are
initially parallel to the ( X ) and ( Y ) axes. Which of the following is the value for the “magnetic flux” associated with the
square loop initially (as in the figure above)?
A ( cdot theta_{S}=frac{B_{0}}{sqrt{2}} l^{prime} )
В . ( theta_{s}=B_{0} l )
c. ( theta_{mathrm{s}}=0 )
D. ( theta_{S}=sqrt{2} B_{0} l^{2} )
12
575Two identical circular loops of ( A & B ) of metal wire are lying on a table without touching each other. Loop A carries a current which increases with time. In
response, the loop B:
A. Remains stationary
B. Is attracted by the loop ( A )
C. Is repelled by the loop ( A )
D. Rotates about its CM, with CM fixed
12
576Which of the following statements can
induced current in Electromagnetic
Induction?
A. Induced current flows such that it increase the total
value of current
B. Induced current flows such that it reduces the total value of current
C. Induced current flows such that direction of magnetic field produced from induced current opposes change in external magnetic field
D. Induced current flows such that direction of magnetic field produced from induced current opposes external magnetic field
12
577Assertion: When number of turns in a
coil is doubled, coefficient of self inductance of the coil becomes 4 times.
Reason: This is because ( boldsymbol{L} propto boldsymbol{N}^{2} )
A. Both Assertion and Reason are true and Reason is the correct explanation of Assertion
B. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
c. Assertion is true but Reason is false
D. Assertion is false but Reason is true
12
578A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is
(i) pushed into the coil
(ii) withdrawn from inside
the coil (iii) held stationary inside the coil.
12
579Force which is required to maintain the
velocity of the rod at that instant.
12
580A dynamo converts:
A. electrical energy into mechanical energy
B. electrical energy into heat energy
C. mechanical energy into electrical energy
D. heat energy into electrical energy
12
581Two parallel rails with negligible
resistance are ( 10.0 mathrm{cm} ) apart and are
connected by a ( 5.00 Omega ) resistor. The
circuit also contains two metal rods
having resistance of ( 10.0 Omega ) and ( 15.0 Omega )
sliding along the rails. The rods are
pulled away from the resistor at a
constant speeds ( 8.00 m / s ) and ( 4.00 m / s ) respectively. A uniform magnetic field
( 0.010 T ) is applied perpendicular to the
plane of the rails. Determine the current
in the ( 5.00 Omega ) resistor.
12
582A current of ( 2 A ) is passed through a coil
of 1000 turns to produce a flux of
( 0.5 mu W b . ) Self inductance of the coil
A ( .2 .5 times 10^{-4} H )
В. ( 2.5 times 10^{-5} H )
c. ( 2.5 times 10^{-6} H )
D. ( 2.5 times 10^{-7} H )
12
583Consider the time interval ( t=0 ) to ( t= )
( mathbf{2 . 0 s} )
The magnetic field is perpendicular to
the plane of the loop.
12
584Assertion
An electric motor will have maximum
efficiency when back emf becomes equal to half of applied emf.
Reason
Efficiency of electric motor depends only on magnitude of back emf.
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
585x x
X
x
x x
x
X
x
x
(d) current Hows in anticlockwise wirection
31. A metallic ring of radius r with a uniform metallic spe
of negligible mass and length ris rotated about its a
with angular velocity o in a perpendicular uniform
magnetic field B as shown in figure. The central end of
the spoke is connected to the rim of the wheel through
resistor R as shown. The X X X X X
resistor does not rotate, its one
end is always at the center of
the ring and the other end is X
always in contact with the
ring. A force F as shown is
needed to maintain constant X
angular velocity of the wheel.
F is equal to (the ring and the X X X X X
spoke has zero resistance)
B²wr²
8R
B²wr3
C2R
4R
A conducting ring
+
X
x
x
(a)
(b)
Bor2
2R
B²wr3
(d) AR
32
12
586When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage
A . increases
B. decreases
c. remains constant
D. reaches zero
12
587( ln operatorname{an} A C ) Generator, if the number of
turns for the armature coil is doubled
keeping all other specifications to be the same, which of the following applies to the voltage generated
A. Peak Voltage will remain the same but the rms value of Voltage generated double
B. Peak Voltage will double but the rms value of Voltage generated will remain the same
c. Both the peak Voltage and the rms value of Voltage generated will double.
D. Both the peak Voltage and the rms value of Voltage generated will reduce to half the original value
12
588Assertion
Electromotive force is a force which
help the electrons to flow and produce
current.
Reason
Electromotive force is independent of
the voltage across the cell
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
589A long solenoid has 1000 turns. When a
current of ( 4 A ) flows through it, the
magnetic flux linked with each turn of
the solenoid is ( 4 times 10^{-3} ) Wh. The self-
inductance of the solenoid is:
A. 4 н
в. 3 н
( c .2 H )
D. 1
12
590The magnetic fields through two identical rings made of copper and wood are changing at the same rate. The induced electric field in copper ring will be :
A. more than that in the wooden ring
B. less than that in the wooden ring
c. finite and that in the wooden ring will be zero
D. same as that in the wooden ring
12
591( = )
( b )
( b )
( b )
12
592coils which lie in a uniform magnetic
field. Plane of the coils is perpendicular
to the magnetic field as shown in figure.
The coil is connected to a current
integrator which measures the total
charge passing through it. The coil is
turned through ( 180^{circ} ) about the
diameter. The charge passing through the coil is
( ^{mathbf{A}} cdot frac{N B A}{R} )
B. ( frac{sqrt{3} N B A}{2 R} )
c. ( frac{N B A}{sqrt{2} R} )
D. ( frac{2 N B A}{R} )
12
593Fleming’s right hand is also called as
A. generator rule
B. dynamo rule
c. system rule
D. none
12
594The dimensional formula for magnetic flux is
A ( cdotleft[M L^{2} T^{-2} A^{-1}right] )
B ( cdotleft[M L^{3} T^{-2} A^{-2}right] )
c. ( left[M^{0} L^{-2} T^{-2} A^{-2}right] )
D・ ( left[M L^{2} T^{-1} A^{2}right] )
12
595In a DC generator,the induced e.m.f in the armature is
A. DC
B. AC
c. Fluctuating DC
D. Both AC and DC
12
596In a magnetic field of ( 0.05 T ) area of coil
changes from ( 101 c m^{2} ) to ( 100 c m^{2} )
without changing the resistance which is ( 2 Omega . ) The amount of charge that flow during this period is
A ( cdot 2.5 times 10^{-6} C )
B . ( 2 times 10^{-6} C )
c. ( 10 times 10^{-6} C )
D. ( 8 times 10^{-6} C )
12
597The electric flux through a certain area of dielectric is ( 8.76 times 10^{3} t^{4} ). The
displacement current through the area
is ( 12.9 p A ) at ( t=26.1 m s . ) Find the
dielectric constant of the material.
A ( .2 times 10^{-8} )
B. ( 4 times 10^{-8} )
c. ( 8 times 10^{-8} )
D. ( 2 times 10^{-7} )
12
598An emf will not be inducted in the coil, if ?12
599A loop of area ( 1 m^{2} ) is placed in a
magnetic field ( B=2 T ), such that plane
of the loop is parallel to the magnetic
field. If the loop is rotated by ( 180^{circ}, ) the
amount of net charge passing through any point of loop, if its resistance is
( 10 Omega ) is :
A. ( 0.4 C )
B. ( 0.2 C )
( c .0 .8 C )
D. ( 0 C )
12
600To convert mechanical energy into
electrical energy, one can use
A. DC dynamo
B. AC dynamo
c. motor
D. (A) & (B)
12
601Two parallel rails of a railway track
insulated from each other and with the
ground are connected to a millivoltmeter. The distance between
the rails is one metre. A train is
traveling with a velocity of ( 72 k m / h )
along the track. The reading of the millivoltmeter ( (text { in } boldsymbol{m} boldsymbol{V}) ) is :
(Vertical component of the earths
magnetic induction is ( left.2 times 10^{-5} Tright) )
A. 144
в. 0.72
c. 0.4
D. 0.2
12
602State True or False:
Dynamo output can be coupled to a transformer.
A. True
B. False
12
603To measure the field ( B ) between the
poles of an electromagnet, a small test loop of area ( 1 mathrm{cm}^{2} ), resistance ( 10 Omega ) and 20 turns is pulled out of it. A galvanometer shows that a total charge of ( 2 mu C ) passed through the loop. The
value of ( B ) is
A . ( 0.001 T )
в. ( 0.01 T )
( c .0 .17 )
D. ( 1.0 T )
12
604A conducting slider of resistance
( R(10 Omega), ) mass ( 50 g & ) length10cm is
kept on a U-shaped frame as shown in
figure. There is uniform magnetic field
( (B=0.1 T) ) perpendicular to plane of
frame. The slider is attached to a spring ( (K=0.5 N / m) . ) The slider is displaced
by an amount ( A_{0} & ) released. Time in
which its amplitude become ( A_{0} / e ) is
A . ( 9000 s )
B. 10000 s
c. ( 12000 s )
D. 15000 s
12
605If ( 0.1 J ) of energy is stored for the flow of current of ( 0.2 A ) in an inductor, then its
inductance value is:
A ( .5 H )
в. ( 0.5 H )
( mathrm{c} cdot 5 m H )
D. ( 50 H )
E . ( 50 mathrm{mH} )
12
606A solenoid has 2000 turns wound over a
length of ( 0.3 m . ) The area of its cross section is ( 1.2 times 10^{-3} m^{2} . ) Around its
cross section a coil of 300 turns is
wound. If an initial current of ( 2 A ) is
reversed in ( 0.25 s, ) the emf induced in
the coil is equal to
A ( cdot 6 times 10^{-4} V )
В. ( 4.8 times 10^{-2} V )
c. ( 2.4 times 10^{-2} V )
D. ( 48 k V )
12
607In the figure shown ABCDEFGH is a
square conducting frame of side ( 2 m )
and resistance ( 1 Omega / m . ) A uniform magnetic field B is applied perpendicular to the plane and pointing
inwards. It increases with time at a
constant rate of ( 10 T / s . ) Then: ( (A B=B C )
( =C D=B H=1 m) )
rhis question has multiple correct options
A. current in DH arm is zero
B. power consumed as heat in the circuit 200 watt
C. heat produced in DH and BF arm is zero
D. current in AG and CB arm is equal and its magnitude ( 5 A )
12
608( ln ) an ( A C ) generator, the rate of change of
magnetic flux through the coil is maximum when the angle between the
plane of the coil and the lines of force is
A . ( 0^{circ} )
B. ( 60^{circ} )
( c cdot 30^{circ} )
D. ( 90^{circ} )
12
609A thin circular ring of area ( A ) is held perpendicular to a uniform magnetic field of induction B. A small cut is made
in the ring and a galvanometer is
connected across the ends such that
the total resistance of the circuit is ( mathrm{R} ).
When the ring is suddenly squeezed to
zero area, the charge flowing through
the galvanometer is
A. ( frac{B R}{A} )
в. ( frac{B A}{R} )
c. ABR
D. ( frac{B^{2} A}{R^{2}} )
12
610What replacement is required to
convert an AC generator to DC generator
?
A. Armature with coil
c. Slip rings with split rings
D. All of the above
12
611A metal rod moves at a constant
velocity in a direction perpendicular to its length. A constant uniform magnetic field exists in space in a direction perpendicular to the rod as well as its velocity. Select the correct statement(s) from the following:
A. The entire rod is at the same electric potentia
B. There is an electric field in the rod
c. The electric potential is highest at the center of the rod and decrease toward its ends
D. The electric potential is lowest at the center of the rod and increases toward its ends
12
612Two metallic rings of radius ( R ) are
rolling on a metallic rod. A magnetic
field of magnitude ( B ) is applied in the
region. The magnitude of potential
difference between points ( A ) and ( C ) on
the two rings (as shown), will be:
( A )
в. ( 4 B omega R^{2} )
( mathbf{c} cdot 8 B omega R^{2} )
( D cdot 2 B omega R^{2} )
12
613Eddy currents are produced in a
metallic conductor when
A. The magnetic flux linked with it changes
B. It is placed in a changing magnetic field
C. It is placed in a magnetic field.
D. Both A and B
12
614If radius of long solenoid is reduced to half of original without changing other physical factor,then its self inductance
will change-
A. ( 1 / 3 ) times
B. ( 1 / 2 ) times
c. ( 1 / 5 ) times
D. ( 1 / 4 ) times
12
constant angular velocity ( boldsymbol{omega}=frac{1}{sqrt{L C}} )
with the help of an external agent. A
uniform magnetic field B exists in
space and is directed into the plane of
the figure. (circuit part remains at rest
(left part is at rest) ). Then,
This question has multiple correct options
A the rms value of current in the circuit is ( frac{pi B a^{2}}{R sqrt{2 L C}} )
B. the rms value of current in the circuit is ( frac{pi B a^{2}}{2 R sqrt{L C}} )
c. the maximum energy stored in the capacitor is ( frac{pi^{2} B^{2} a^{4}}{8 R^{2} C} )
D. the maximum power delivered by the external agent is ( frac{pi^{2} B^{2} a^{4}}{4 L C R} )
12
616One conducting U tube can slide inside another as shown in figure, maintaining electric contacts between the tubes. The
magnetic field B is perpendicular to the plane of the figure. If each tube moves
towards the other at a constant speed ( v )
then the emf induced in the circuit in
terms of ( mathrm{B}, l ) and ( mathrm{v} ) where ( l ) is the width of
each tube, will be
A . -Blv
в. Вlv
c. 2 вlv
D. zero
12
617Match column I and column II and
select the correct answer using the codes given below:
12
618(4)
2.0 X10
J
1
The four wire loops shown in figure have vertical edge
lengths of either L, 2L, or 3L. They will move with the
same speed into a region of uniform magnetic field B
directed out of the page. Rank them according to the
maximum magnitude of the induced emf greatest to least.
BO
1
2
3
(a) 1 and 2 tie, then 3 and 4 tie
(b) 3 and 4 tie, then 1 and 2 tie
(c) 4, 2, 3,1
(d) 4 then 2 and 3 tie, and then 1
12
619As shown in above figure, a uniform
magnetic field B, direction of magnetic
field is outward of the plane of the page.
Calculate the potential difference
between point a and b if metal rod is
pulled upward with constant velocity.
A .
B. ( frac{1}{2} v B L ), with point a at the higher potential
C ( cdot frac{1}{2} v B L, ) with point ( b ) at the higher potential
D. vBL, with point a at the higher potential
E. vBL, with point b at the higher potential
12
620Analyse the first pair and complete the
second pair
[
text { Battery: } overbrace{^{2}}{mid sqrt{mathrm{TIME}} longrightarrow} quad text { DC Generator: }
]
12
621Assertion
The coil in the resistance boxes are
Reason
Thick wire is required in resistance box.
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
622The flux linked with a coil changes with
time according to the equation ( phi=a t^{2} ) ( +b t+c . ) Then Sl unit of a is
A. volt
B. Volt/sec
c. volt.sec
D. weber
12
623A pair of adjacent coil has a mutual
inductance of ( 1.5 mathrm{H} ). If the current in
one coil changes from 0 to ( 20 A ) in 0.5
sec, what is the change of flux linkage with the other coil?
12
624Refer to the figure. When does the the
galvanometer (G) deflect?
A. The magnet is pushed into the coil
B. The magnet is rotated into the coil
c. The magnet is stationary at the centre of the coil.
D. The number of turns in the coil is reduced
12
625When a wire loop is rotated in a magnetic field, the direction of induced emf changes in every
A. one revolution
B. ( frac{1}{2} ) revolution
c. ( frac{1}{4} ) revolution
D. 2 revolution
12
626In the given figure, a bar magnet is quickly moved towards a conducting loop having a capacitor. Predict the
polarity of the plates ( A ) and ( b ) of the capacitor.
12
627If we use a powerful electromagnet in place of permanent magnet in a
generator, then:
A. voltage produced by the generator increases
B. current produced by the generator increases.
c. Both A and B are true
D. No effect on current or voltage occurs.
12
628A dynamo consists of
A. a horse-shoe magnet
B. an armature coil
C . two slip rings
D. all of these
12
629If the turns ratio of a transformer is 2
and the impedance of primary coil is 250 W then the impedance of secondary coil will be
A . ( 1000 Omega )
B. 500 ( Omega )
( c cdot 250 Omega )
D. 125 ( Omega )
12
63019. The network shown in the figure is a part of a compla
circuit. If at a certain W h o novom
instant the current i is 5 12 15 V 5 mH B
A and is decreasing at the rate of 10° A/s then V-V.
(a) 5V (b) 10 V (c) 15 V (d) 20 V
12
631In a DC generator, induced emf in the armature is
A. DC
B. AC
c. fluctuating DC
D. both ( A C ) and ( D C )
12
632Explain why an induced current must flow in such a direction so as to oppose
the change producing it
12
633A solenoid coil is wound on a frame of
rectangular cross section. If all the linear dimension of the frame are
increased by a factor of two and the number of turns per unit length of the coil remains the same, the self-
inductance increases by a factor of
A .4
B. 8
c. 12
D. 16
12
634Which end of the inductor, ( a ) or ( b ), is at a
higher potential?
12
635What is an AC generator? Obtain an expression for the sinusoidal emf induced in the coil of ac generator,
rotating with a uniform angular speed in a uniform magnetic field.
12
636Lenz’s law is a consequence of the law of conservation of
A. charge
B. mass
c. energy
D. momentum
12
637The magnetic flux in a coil of 100 turns increases by ( 12 times 10^{3} ) Maxwell in 0.2
second due to the motion of a magnet. The emf induced in the coil will be
( A cdot 6 v )
B. ( 0.6 v )
c. ( 0.06 v )
D. 60 V
12
638Consider the time interval ( t=2.0 s ) to
( boldsymbol{t}=mathbf{4} . mathbf{0} boldsymbol{s} )
The magnetic field is perpendicular to
the plane of the loop.
12
6393. Two coils are placed close to each other. The mutual
inductance of the pair of coils depends upon
(a) the currents in the two coils.
(b) the rates at which currents are changing in the two
coils.
(c) the relative position and orientation of the two coils
(d) the material of the wire of the coils (AIEEE 2003)
12
640The self inductance of a motor of an
electric fan is ( 10 H . ) In order to impart
maximum power at ( 50 H z ), it should be
connected to a capacitance of :
A ( .4 mu F )
в. ( 8 mu F )
( mathrm{c} cdot 1 mu F )
D. ( 2 mu F )
12
641The uniform magnetic field perpendicular to the plane of a conducting ring of radius a changes at
the rate of ( alpha, ) then
This question has multiple correct options
A. all the points on the ring are at the same potential
B. the emf induced in the ring is ( pi a^{2} alpha )
C. electric field intensity ( E ) at any point on the ring is zero
( mathbf{D} cdot E=(a alpha) / 2 )
12
642Crosses represent uniform magnetic
field directed into the paper. A conductor XY moves in the field towards
right side. Find the direction of induced
current in the conductor. Name the rule
you applied. What will be the direction of current if the direction of field and
the direction of motion of the conductor
both are reversed?
12
643The average induced emf in the circuit
is
( mathbf{A} cdot 0.2 V )
B. ( 0.1 V )
( mathbf{c} cdot 1 V )
D. ( 10 V )
12
644toppr
The space between the conductors is
filled with air. The inner and outer
conductors are carrying currents of
equal magnitudes and in opposite directions

Then the variation of magnetic field
with distance from the axis is best
plotted as:
4
3
( c )
2

12
645A short magnet is allowed to fall from
rest along the axis of a horizontal conducting ring. The distance fallen by the magnet in one second may be
( A cdot 5 m )
в. ( 6 m )
( c .4 m )
D. None of these
12
646Match the following:
Quantity Formula
1) Magnetic c flux with
a) ( -N frac{d phi}{d t} )
2)
Induced emf
b) ( mu_{r} mu_{0} n_{1} n_{2} pi r_{1}^{2} l )
3) Force on a charged particle
( cdots ) moving in a electric and
c) ( B A cos theta )
magnetic field
( f a ) 4) Mutual inductance of
solenoid d)
[
q(bar{E}+bar{v} times bar{B})
]
( A cdot 1-c, 2-d, 3-b, 4-a )
B. ( 1-c, 2-a, 3-d, 4-b )
( mathbf{C} cdot 1-mathbf{b}, 2-mathbf{a}, mathbf{3}-mathbf{c}, mathbf{4}-mathbf{d} )
D. ( 1-a, 2-b, 3-d, 4-c )
12
647While 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. ( frac{1}{4} ) times the original valu
D. Unaffected
12
648An inductor may store energy in:
A. its electric field
B. its coil
C . its magnetic field
D. both electric and magnetic fields
12
649A triangular loop is placed in a dot ( Theta ) magnetic field as shown in figure. The
direction of induced current is
clockwise in the loop if magnetic field is
12
650What is a generator state the principle
on which generators work
12
651A conducting ring of radius ( r ) and
resistance ( boldsymbol{R} ) rolls on a horizontal
surface with constant velocity ( v ). The
magnetic field ( B ) is uniform and is
normal to the plane of the loop. Choose
the correct option.
A. The induced emf between ( O ) and ( Q ) is ( B r v )
B. ( _{text {An induced current } I}=frac{2 B v r}{R} ) flows in the clockwise
direction
Conduced current ( I=frac{2 B v r}{R} ) flows in the
anticlockwise direction
D. No current flows
12
652What will be the magnitude of e.m.f. induced in a 200 turns coil with cross
section area ( 0.16 m^{2} ? ) The magnetic field through the coil changes from 0.10 Wb ( m^{-2} ) to ( 0.30 mathrm{Wb} ), at a uniform rate over a
period of ( 0.05 mathrm{s} )
A . ( 128 v )
B. 130v
( c cdot 118 v )
D. 1320
12
653Which of the following statement is
correct regarding induced electric field (symbols have their usual meanings)? This question has multiple correct options
A. Work done in moving a test charge in an induced electric field can be zero
B. Induced electric field is non-conservative is nature
C. Induced electric lines of force form closed loops
D. Induced e.m.f. in the loop in ( varepsilon=oint vec{E} . overline{d iota}=-frac{d phi}{d t} )
12
at the rate of ( 10^{2} mathrm{m} / mathrm{s} ). A constant and
uniform magnetic field of induction ( 10^{3} W b / m^{2} ) acts perpendicular to the plane of the coil. The radius of the coil when the induced e.m.f. in the coil is ( 1 mu )
( v, ) is
( ^{A} cdot frac{2}{pi} mathrm{cm} )
в. ( frac{3}{pi} mathrm{cm} )
c. ( frac{4}{pi} mathrm{cm} )
D. ( frac{5}{pi} mathrm{cm} )
12
655A square wire loop of ( 10.0 mathrm{cm} ) side lies
at right angles to a uniform magnetic field of 7 T. A 10 V light bulb is in series with the loop as shown in figure. The magnetic field is decreasing steadily to zero over a time interval ( Delta t . ) For what
value if ( Delta t(text { in } m s), ) the bulb will shine
with full brightness?
12
656Determine the magnetic flux through
the smaller loop as a function of ( x )
A ( cdot frac{mu_{0} i R^{2} pi r^{2}}{x^{3}} )
B. ( frac{mu_{0} i R^{2} pi r^{2}}{2 x^{3}} )
c. ( frac{2 mu_{0} i R^{2} pi r^{2}}{x^{3}} )
D. ( frac{sqrt{2} mu_{0} i R^{2} pi r^{2}}{x^{3}} )
12
657A rectangular loop PQRS, is being pulled
with constant speed into a uniform
transverse magnetic fieldby a force (as shown). E.m.f. induced in side PS
and potential difference between points
Pand S respectively are (Resistance of the ( operatorname{loop}=r) )
A ( cdot ) zero, ( frac{F r}{B ell} )
B. Zero, zero
c. zero, ( frac{F r}{6 B ell} )
D. ( frac{F r}{6 B ell}, frac{F r}{6 B ell} )
12
658A square loop of side ( a ) and a straight
long wire are placed in the same plane as shown in figure. The loop has a
resistance ( boldsymbol{R} ) and inductance ( boldsymbol{L} ). The
frame is turned through ( 18^{circ} ) about the
axis ( O O^{prime} . ) What is the electric charge
that flows through the loop?
( ^{mathbf{A}} cdot frac{mu_{0} I a}{2 pi R} ln left(frac{2 a+b}{b}right) )
в. ( frac{mu_{0} I a}{2 pi R} ln left(frac{b}{b^{2}-a^{2}}right) )
c. ( frac{mu_{0} I a}{2 pi R} ln left(frac{a+2 b}{b}right) )
D. None of these
12
659A long solenoid with length ( l ) and a
radius ( R ) consists of ( N ) turns of
wire,Neglecting the end effects, find the self-inductance.
B . ( mu_{0} N pi R^{2} / l )
c. ( mu_{0} N^{2} pi R^{3} l )
D. ( mu_{0} N^{3} pi R^{2} l )
12
660A conducting wire in the shape of ( Y )
with each side of length ( l ) is moving in a uniform magnetic field B, with a uniform speed v as shown in the figure.
The induced emf at the two ends ( X ) and
Y of the wire will be
A. zero
в. 2Blv
( c . ) 2Blv ( sin (theta / 2) )
D. 2Blv ( cos (theta / 2) )
12
661Flux ( Phi ) (in weber) in a closed circuit of
resistance 10 ohm varies with time ( t ) (in
sec) according to the equation ( Phi=6 t^{2}- )
( 5 t+1 . ) What is the magnitude of the
induced current at ( t=1 ) sec?
A . ( 0.5 A )
в. ( 0.6 A )
( c .0 .7 A )
D. ( 0.8 A )
12
662The Sl unit of inductance, the henry, can
be written as:
A. Weber ampere ( ^{-1} )
B. Volt-s ampere-
c. Joule ampere-
D. ohm ( s^{-1} )
12
663A system ( S ) consists of two coils ( A ) and
B. The coil ( A ) have a steady current ( I )
while the coils ( B ) is suspended near by
as shown in figure. Now the system is
heated as to raise the temperature of
A. the two coils show attraction
B. the two coils show repulsion
C. there is no change in the position of the two coils
D. induced currents are not possible in coil ( B )
12
664A coil of inductance ( L ) is carrying a
steady current I what is the nature of its stored energy?
A. Magnetic
B. Electrical
c. Both magnetic and electrical
D. Heat
12
665A commutator changes the direction of current in the coil of
A. a DC motor
B. a DC motor and an AC generator
c. a DC motor and a DC generator
D. an Ac generator
12
666The horizontal component of the earth’s magnetic field at a place is ( 3 times 10^{-4} T )
and the dip is ( theta=tan ^{-1}(4 / 3) . ) A metal
rod of length ( 0.25 mathrm{m} ) placed in the north south position is moved at a constant speed of ( 10 mathrm{cm} / mathrm{s} ) towards the east. The
e.m.f induced in the rod will be:
A. zero
B. ( 1 mathrm{mV} )
( c cdot 5 m v )
D. 10 mv
12
667A 10 V battery connected to ( 5 Omega )
resistance coil having inductance ( 10 mathrm{H} ) through a switch drives a constant
current in the circuit. The switch is
suddenly opened and the time taken to open it is 2 ms. The average emf
induced across the coil is
A ( cdot 4 times 10^{4} )
B ( .2 times 10^{4} )
( c cdot 2 times 10^{2} )
D. ( 1 times 10^{4} )
12
668Deflection in the galvanometer
A. Towards right
B. Left
c. No defection
D. None of these
12
669Current is induced in a coil by
electromagnetic induction when:
A. Only the coil moves in a magnetic field.
B. Only the magnet moves towards the coil.
C. Coil and the magnet move with respect to each other
D. None of the above
12
670A coil of self inductance ( 2 cdot 5 H ) and
resistance ( 20 Omega ) is connected to a
battery of emf 120V having internal
resistance of ( 5 Omega ). Find the current in the
12
671The figure given shows the variation of
an alternating emf with time. What is the average value of the emf for the
A . 100
B. 200
( c .300 )
D. 400
12
672If the coil of the generator starts rotating faster then:
A. voltage produced by the generator increases.
B. current produced by the generator increases.
c. Both A and B
D. No effect on the value of current and voltage
12
67374. In the given figure two concentric cylindrical region in
which time varying magnetic field is present as shown.
From the center to radius R
magnetic field is perpendicular
into the plane varying as dB/dt =
2ko and in a region from R to 2R
magnetic field is perpendicular
out of the plane varying as dB/
3RB
dt = 4ko. Find the induced emf
across an arc AB of radius 3R.
(a) 6Rºko
(b) 5Rľke
(c) 7Rºke
(d) none of these
12
674The device which converts the
mechanical energy in to electric energy is
A . D.C. motor
B. A.C. dynamo
c. Transformer
D. starter
12
675The self inductance of a coil having 400 turns is ( 10 mathrm{mH} ). The magnetic flux through the cross section of the coil corresponding to Current ( 2 mathrm{mA} ) is
( mathbf{A} cdot 4 times 10^{-5} mathbf{W} mathbf{b} )
B. ( 2 times 10^{-3} mathrm{wb} )
( c cdot 3 times 10^{-5} w b )
D. ( 8 times 10^{-3} mathrm{wb} )
12
676What will be the polarities at ( A & B ) if the direction of current is reversed in
the circuit??
12
677Strength of magnetic field is defined as
A. Number of field lines passing normally through a unit surface
B. Electric field lines passing the loop
C. Current through surface
D. Number of electrons passing a specific point per unit time
12
678Two inductance’s connected in parallel are equivalent to a single inductance of
( 1.5 H, ) and when connected in series
are equivalent to a single inductance of
( 8 H . ) The difference in their inductance
is:-
( mathbf{A} cdot 3 H )
в. ( 7.5 ~ H )
c. ( 2 H )
D. ( 4 H )
12
679A rectangular copper coil is placed in uniform magnetic field of induction
( 40 m T ) with its plane perpendicular to
the field. The area of the coil is
shrinking at a constant rate of ( 0.5 m^{2} s^{-1} ). The emf induced in the coil is
A . ( 10 mathrm{mV} )
в. ( 20 mathrm{mV} )
c. ( 80 m V )
D. ( 40 mathrm{mV} )
12
68021
UUUU
(c) A
13. The flux linked with a coil at any instant t is given by
0= 10r – 50t + 250. The induced emf at t = 3 s is
(a) 10 V
(b) 190 V
(c) -190 V
(d) -10 V (AIEEE 2006)
12
681(AILLE 200)
2. A conducting square loop of
side L and resistance R moves
in its place with a uniform
velocity v perpendicular to
one of its sides. A magnetick
induction B, constant in time and space, pointing
perpendicular and into the plane at the loop, exists
everywhere with half the loop outside the field, as shown
in the figure. The induced emf is
(a) zero
(b) RvB
(d) vBL (AIEEE 2002)
R
o VBL
rout
12
682A rectangular frame of wire abcd has
dimensions ( 32 mathrm{cm} times 8.0 mathrm{cm} ) and a total
resistance of ( 2.0 Omega . ) It is pulled out of a
magnetic field ( B=0.020 T ) by applying
a force of ( 3.2 times 10^{-5} N ) (figure). It is
found that the frame moves with
constant speed. What is constant speed
of the frame?
12
683A vertical rod of length ( l ) is moved with
constant velocity ( v ) towards east. The
vertical component of earth’s magnetic
field is ( mathrm{B} ) and angle of dip is ( theta . ) The induced e.m.f. in rod is:
A. ( B l v cot theta )
B. ( B l v sin theta )
c. ( B l v tan theta )
D. ( B l v cos theta )
12
684A domestic electrical appliance requires alternating current of ( 15 mathrm{V} ). If
( 220 mathrm{V} ) of alternating current is supplied to the house, then the device that helps in the functioning of that electrical appliance is
A. Induction coil
B. Step-up transformer
c. AC dynamo
D. Step-down transformer
12
685Two coaxial coils are very close to each
other and their mutual inductance is
( 5 m H . ) If a current 50 sin500t is passed
in one of the coils then the peak value of induced emf in the secondary coil will
be
A . ( 5000 V )
B. ( 500 V )
( mathbf{c} cdot 150 V )
D. ( 125 V )
12
686Mention any two applications of eddy
currents.
12
687Assertion
It is more difficult to push a magnet
into a coil with more loops.
Reason
Emf induced in the current loop resists
the motion of the magnet.
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
688A ( 1.0 mathrm{m} ) long metallic rod is rotated with
an angular frequency of 400 rad ( s^{-1} )
about an axis normal to the rod passing through its one end. The other end of the
rod is in contact with a circular metallic
ring. A constant and uniform magnetic field of 0.5 T parallel to the axis exists everywhere. Calculate the emf developed between the centre and the
ring.
12
689A coil of inductance 1 henry and
resistance ( 10 Omega ) is connected to an ideal
battery of emf ( 50 mathrm{V} ) at time ( t=0 )

Calculate the ratio of the rate at which
magnetic energy is stored in the coil to the rate at which energy is supplied by the battery at ( t=0.1 ) sec.
A.
в. ( frac{1}{e-1} )
( c cdot_{1-frac{1}{e}} )
( D cdot frac{1}{e} )

12
690XX
X X X X X
(u) 90
22. A rectangular loop with a sliding conductor of length l is
located in a uniform magnetic field perpendicular to the
plane of the loop (figure).
The magnetic induction is X
B. The conductor has a X
resistance R. The sides AB
and CD have resistances
R, and R2, respectively.
Find the current through X
the conductor during its
motion to the right with a
constant velocity v.
Blv(R+R)
BI?
(b)
R (R₂ + R₂)
R₂ + R, R₂
Blv(R+R)
BI?
R, R₂ + R(R₂ + R₂)
R, R₂ + R(R₂ + R₂)
X X X X X X X
X X X X X X X X X X
X X X X
mimo
XXXXXXX
(a)
A
vtola
1
12
691A circular coil has 500 turns of wire and
its radius is ( 5 mathrm{cm} ). The self inductance of
the coil is:-
A ( cdot 25 times 10^{-3} m H )
в. ( 25 m H )
c. ( 50 times 10^{-3} H )
D. ( 50 times 10^{-3} mathrm{mH} )
12
692The coefficient of mutual inductance of
the two coils is ( 5 H . ) The current through the primary coil is reduced to zero value
from ( 3 A ) in 1 millisecond. The induced
emf in the secondary coils is
A. zero
в. 1.67 Кル
c. ( 15 K V )
D. ( 600 V )
12
693The phenomenon of electromagnetic
induction is :
A. the process of charging a body
B. the process of generating magnetic field due to a current passing through a coil
C. producing induced current in a coil due to relative motion between a magnet and the coil
D. the process of rotating a coil of an electric motor
12
694Draw a labelled diagram of an electric
generator
12
695When a rectangular coil is rotated in a uniform magnetic field about an axis passing through its centre and perpendicular to the field, the induced
emf in the coil is maximum when the
plane of the coil is
A. Perpendicular to the field
B. Parallel to the field
c. Inclined at 60 with the field direction
D. Inclined at 45 with the field direction
12
696A long solenoid of radius ( R ) carries a time (t)-dependent current ( boldsymbol{I}(boldsymbol{t})= )
( boldsymbol{I}_{0} boldsymbol{t}(mathbf{1}-boldsymbol{t}) cdot mathbf{A} ) ring of radius ( 2 boldsymbol{R} ) is placed
coaxially near its middle. During the
time interval ( 0 leq t leq 1, ) the induced
current ( left(I_{R}right) ) and the induced
( boldsymbol{E} boldsymbol{M} boldsymbol{F}left(boldsymbol{V}_{boldsymbol{R}}right) ) in the ring change as:
( mathbf{A} cdot ) At ( t=0.5 ) direction of ( I_{R} ) reverses and ( V_{R} ) is zero.
B. Direction if ( I_{R} ) remains unchanged and ( V_{R} ) is zero at ( t=0.25 )
C . At ( t=0.25 ) direction of ( I_{R} ) reverses and ( V_{R} ) is maximum.
D. Direction of ( I_{R} ) remains unchanged and ( V_{R} ) is maximum at ( t=0.5 )
12
697There is a uniform (in spatial districution) magnetic filed B in a circular region of radius ( R ) as shown in
the figure whose magnitude varies uniformly a the rate ( beta ) w.r.t. time. The emf induced across the ends of a
circular concentric conducting arc of
radius ( R_{1} ) having an agle ( theta ) as shown
( left(<boldsymbol{O} boldsymbol{A} boldsymbol{O}^{prime}=boldsymbol{theta}right) ) is
( ^{mathrm{A}} cdot frac{theta}{2 pi} R_{1}^{2} cdot beta )
B. ( frac{theta}{2} R^{2} cdot beta )
c. ( frac{theta}{2 pi} R^{2} . ).
D. zero
12
698p is shown in the
20. The current through a 4.6 H inductor is shown
following graph. The induced emf during the time inte
t = 5 milli-sec to 6 milli-sec will be
(a) 10′
(b) – 23 x10 V
(c) 23 x 10’v
(d) Zero
I (Amp)
—–
5
6
(milli sec)
12
699The electrical analog of mass is
A . Diode
B. Capacitance
c. Inductance
D. Resistance
12
700The reading of ( V_{2} ) is :
( ^{mathbf{A}} cdot frac{-pi a^{2} B_{0} R_{1}}{R_{1}+R_{2}} )
( ^{mathbf{B}} cdot frac{-pi a^{2} B_{0} R_{2}}{R_{1}+R_{2}} )
с. ( frac{pi a^{2} B_{0} R_{1}}{R_{1}+R_{2}} )
D. None of these
12
701An inductor of inductance 100 m ( H ) is
connected in series with a resistance, a variable capacitance and an AC source of frequency ( 2.0 mathrm{kHz} ); The value of the
capacitance so that maximum current
may be drawn into the circuit.
( A cdot 50 mathrm{nF} )
B. 60 nF
( c cdot 63 ) nf
D. 79 nf
12
702A conducting rod ( A B ) moves parallel to the x-axis in a uniform magnetic field
pointing in the positive z direction. The
end ( A ) of the rod gets positively charged. explain.
12
703Production of electricity from magnetism is called
A . electric field
B. magnetic field lines
c. electromagnetic induction
D. magnetic induction
12
704The magnitude of the EMF in a coil depends on
A. flux density passing through it
B. density of material
c. amount of flux leakage
D. rate of change of flux linkages
12
705A solenoid of length ( 1 m ) and ( 0.05 m )
diameter has 500 turns. If a current of
( 2 A ) passes through the coil, calculate
the co-efficient of self induction of the
coil.
12
706A straight conductor ( 0.1 mathrm{m} ) long moves in a uniform magnetic field ).1T. The velocity of the conductor is ( 15 mathrm{m} / mathrm{s} ) and is directed perpendicular to the field The e.m.f. induced between the two ends
of the conductors is.
A . ( 0.10 mathrm{v} )
B. 0.15 ( v )
c. ( 1.50 v )
D. 15.00
12
707Find the speed of the connector as a
function of time if the force ( boldsymbol{F} ) is applied
( operatorname{at} t=0 )
12
708In the circuit shown in figure, a
conducting wire ( H E ) is moved with a
constant speed ( boldsymbol{v} ) toward left. The
complete circuit is placed in a uniform magnetic field ( vec{B} ) perpendicular to the plane of the circuit inward. The current
in ( boldsymbol{H} boldsymbol{K} boldsymbol{D} boldsymbol{E} ) is
A . clockwise
B. anticloclwise
c. alternating
D. zero
12
709Which is the correct formula for
calculating the power lost due to eddy currents per unit mass for a thin sheet
or wire?? Where ( P ) is the power lost per
unit mass ( (W / k g), B_{p} ) is the peak
magnetic field ( (T), d ) is the thickness of the sheet or diameter of the wire ( (boldsymbol{m}), boldsymbol{f} )
is the frequency ( (H z), k ) is a constant equal to 1 for a thin sheet and 2 for a
thin wire
( ^{mathrm{A}} cdot_{P}=frac{pi^{2} B_{p}^{2} d^{2} f^{2}}{6 k rho D} )
в. ( quad P=frac{pi^{2} B_{p}^{2} d^{2} f}{k rho D} )
( ^{mathrm{C}} P=frac{pi^{2} B_{p}^{2} d^{2} f^{2}}{6 k rho D^{3}} )
D. ( P=frac{pi^{2} B_{p}^{2} d^{2} f}{6 k rho D^{2}} )
12
710If emf induced in a coil is ( 2 V ) by
changing the current in it from ( 8 A ) to
( 6 A ) in ( 2 times 10^{-3} s, ) then the coefficient of
self induction is
A ( cdot 2 times 10^{-3} H )
в. ( 10^{-3} H )
c. ( 0.5 times 10^{-3} H )
D. ( 4 times 10^{-3} H )
12
711Self inductance of a long solenoid
depends upon following(s)This question has multiple correct options
A. number of turns
c. length of solenoid
D. none of these
12
712Why self induction is called inertia of
electricity?
12
71326 A ring of mass m, radius r having charge g uniformly
distributed over it and free to rotate about its own axis is
placed in a region having a magnetic field B parallel to
its axis. If the magnetic field is suddenly switched off, the
angular velocity acquired by the ring is
(a) QB
(b) 29B
m
m
(c) 9B
(d) none of these
2m
lenn
I nar unit length is
12
714A feature common to both ( A C ) and ( D C )
generator is
A. Split rings
B. Electrical energy is converted to mechanical energy
c. slip rings
D. Mechanical energy is converted to electrical energy
12
7151 weber is equivalent of
A ( cdot 10^{-8} ) Maxwell
1
B . ( 10^{12} ) Maxwell
c. ( 10^{8} ) Maxwel
D. ( 10^{4} ) Maxwell
12
716The magnetic field perpendicular to the plane of a conducting ring of radius ( r ) changes at the rate ( frac{d B}{d t} ) This question has multiple correct options
A ( cdot ) The emf induced in the ring is ( pi r^{2} frac{d B}{d t} )
B. The emf induced in the ring is ( 2 pi r frac{d B}{d t} )
C. The potential difference between diametrically opposite points on the ring is half of the induced emf.
D. All points on the ring are at the same potential.
12
717If area of a long solenoid is doubled,length is trippled and no. of turns are remained contant.Then its
self-inductance will be changed how many times-
A ( cdot 1 / 3 )
в. ( 2 / 3 )
( c cdot 1 / 9 )
D. ( 4 / 3 )
12
718There is no
generator.
A. ship rings
B. electromagnets
c. commulator
D. generator coil
12
719Electromagnetic induction is not used
in :
A. Transformer
B. Room heater
c. AC generator
D. Choke coil
12
720A flexible wire loop in the shape of a circle has a radius that grows linearly with time. There is a magnetic field perpendicular to the plane of the loop that has a magnitude inversely proportional to the distance from the
center of the loop, ( B(r) propto frac{1}{r} . ) How does
the emf vary with time?
A. ( E propto r^{2} )
в. ( E propto t )
( c cdot E propto sqrt{t} )
D. ( E ) is constant
12
721The magnetic flux linked with a coil is
( phi leq 8 t^{2}+3 t+5 ) Weber. The induced
emf in fourth second will be
( mathbf{A} cdot 16 V )
B. ( 139 V )
( c .67 V )
D. ( 145 V )
12
722A rod lies across frictionless rails in a
uniform magnetic field ( vec{B} ) as shown in
figure. The rid moves to the right with speed ( V . ) In order to make the induced
emf in the circuit to be zero, the
magnitude of the magnetic field should
A. not change
B. increase linearly with time
c. decrease linearly with time
D. decrease nonlinearly with time
12
723The main difference between A.C.
generator and D.C. generator is
A. carbon brushes
B. magnets
c. coil
D. commutator
12
724The diagram shows two circular loops a wire(A and B) centred on and
perpendicular to the ( x ) -axis, and
oriented with their planes parallel to
each other. The y-axis passes vertically through loop A(dashed line). There is a
current ( I_{B} ) in loop ( mathrm{B} ) as shown. Possible
actions which we might perform on loop
( mathbf{A} ) are
A. Move A to the right along x axis closer to B
B. Move A to the left along x axis away from B
C. As viewed from above, rotate A clockwise about y-axis
D. As viewed from above, rotate A anticlockwise about y axis
12
725Which one of the following can produce maximum induced e.m.f.?
A. 50 ampere DC
B. 50 ampere 50 Hz AC
c. 50 ampere 500 нz
D. 100 ampere DC
12
726A coil having 500 square loops each of side ( 10 mathrm{cm} ) is placed normal to a magnetic field which increases at the rate of ( 1 T s^{-1} . ) The induced e.m.f. is
A . 0.1
B. 5.0 V
( c cdot 0.5 v )
D. 1.0
12
727Magnetic flux linked with a stationary loop resistance ( boldsymbol{R} ) varies with respect to
time during the time period ( T ) as
follows:
( phi=a t(T-t) )
The amount of heat generated in the loop during that time (inductance of the coil is negligible) is
A ( cdot frac{alpha T}{3 R} )
В. ( frac{a^{2} T^{2}}{3 R} )
( ^{mathbf{C}} cdot frac{a^{2} T^{2}}{R} )
D. ( frac{a^{2} T^{3}}{3 R} )
12
728A wire ( 88 mathrm{cm} ) long bent into a circular loop is placed perpendicular to the magnetic field of flux density 2.5 Wb
( m^{-2} . ) Within ( 0.5 mathrm{s} ), the loop is changed
into a square and flux density is increased to ( 3.0 mathrm{Wb} mathrm{m}^{-2} ). The value of
e.m.f. induced is :
A . ( 0.018 v )
B. 0.016v
c. ( 0.020 v )
D. 0.012V
12
729Draw a labelled diagram of an ac generator. Obtain the expression for the emf induced in the rotating coil of ( mathrm{N} )
turns each of cross-sectional area ( A ), in
the presence of a magnetic field ( vec{B} ).
12
730Find the magnitude of the magnetic induction B of a magnetic field generated by a system of thin conductors (along which a current ( i ) is flowing) at a point ( A(0, R, 0), ) that is the
centre of a circular conductor of radius
( R ). The circular part is in yz plane.
12
731A device for producing electric current
is
A. Ammeter
B. Voltmeter
c. Generator
D. Galvanometer
12
732Which of the following electrical devices works on the principle of electromagnetic induction?
A. Electric fan
B. Electric bulb
C. Electric cooker
D. L.E.D.
12
733The essential difference between an AC
generator and a DC generator is that
A. AC generator has an electromagnet while a DC generator has permanent magnet.
B. DC generator will generate a higher voltage.
C. AC generator will generate a higher voltage
D. AC generator has slip rings while the DC generator has commutator
12
734A coil has a self-inductance of 0.05
henry. Find magnitude of the emf induced in it when the current flowing through it is changing at the rate
( 100 A s^{-1} )
12
735The north pole of a magnet is moved
into a coil through the end ( boldsymbol{A} ) Simultaneously the north pole of another magnet is moved into the coil through the end ( B ) as shown in the
figure. The direction of induced emf will:
A. Be in the anticlockwise direction as seen through the end ( A )
B. Be in the clockwise direction as seen through the end ( B )
c. Depend on the speed with which the two magnets are moved
D. Depend on the speed with which the magnets are moved and the strengths of the magnets
12
736A circular loop of wire is in the same
place as an infinitely long wire carrying a constant current i. Four possible motion of the loop are marked by ( mathrm{N}, mathrm{E}, mathrm{W} )
and ( mathrm{S} ) as shown.
A clockwise current is induced in the
loop when loop is pulled towards
( A )
B.
( c cdot w )
( D )
12
737Describe the construction and working
of Van de graff generator making the labelled diagram.
12
738Describe one experiment to demonstrate the phenomenon of electromagnetic induction.12
739If given arrangement is moving towards left with speed ( v, ) then potential
difference between ( B ) and ( D ) and current
in the loop are respectively.
A. BvR and non-zero
B. 2BvR and zero
c. 4 Bv ( operatorname{R} ) and non-zer
D. 4BvR and zero
12
740Two circular loops ( P ) and ( Q ) are
concentric and coplanar as shown in
figure. The loop ( Q ) is smaller than ( P . ) If
the current ( I_{1} ) flowing in loop is decreasing with time, then the current
( I_{2} ) in the ( operatorname{loop} Q )
A. flows in the same direction as that of ( P )
B. flows in the opposite direction as that of ( Q )
c. is zero
D. None of these
12
741A metal disc rotates freely, between the
poles of a magnet in the direction
indicated. Brushes ( P ) and ( Q ) make
contact with the edge of the disc and the metal axle. What current, if any,
flows through R?
A. a current from P to Q
B. a current from Q to P
c. no current, because the emf in the disc is opposed by the back emf
D. no current, because the emf induced in one side of the disc is opposed by the emf induced in the other side
E. no current, because no radial emf is induced in the
disc
12
742Assertion
The presence of large magnetic flux through a coil maintains a current in
the coil if the circuit is continuous.
Reason
Magnetic flux is essential to maintain
an Induced current 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
743The emf induced in the circuit is :
( mathbf{A} cdot 2 pi a^{2} B_{0} )
B . ( pi a^{2} B_{0} )
c. ( frac{a^{2} B_{0}}{2} )
D. ( frac{pi a^{2} B_{0}}{2} )
12
744A magnet is dropped free towards a loop of copper wire as shown in figure.
The acceleration of magnet will be :
A. Equal to g
B. Greater than ( g )
c. Less than g
D. zero
12
745Two solenoids of equal number of turns having their length and the radii in the
same ratio ( 1: 2 . ) The ratio of their self-
inductance will be
A .1: 2
B . 2: 1
c. 1: 1
D. 1: 4
12
746The mutual inductance of the system of
two coils is ( 5 m H . ) The current in the
first coil varies according to the
equation ( boldsymbol{I}=boldsymbol{I}_{o} sin boldsymbol{w} boldsymbol{t} ) where ( boldsymbol{I}_{boldsymbol{o}}=mathbf{1 0} boldsymbol{A} )
and ( W=100 pi r a d / s . ) The value of
maximum induced emf in the second
coil is
A ( .2 pi V )
в. ( pi V )
( c .5 pi V )
D. ( 4 pi V )
12
747To obtain maximum EMF from a
number of cells, they must be
connected in
A. Series
B. Parallel
c. Both (a) and (b) above
D. None of these
12
748Is this device feasible?
A. Yes
B. no
C. depends on the availability of material
D. maybe or may not be
12
749netic poooooo
45. A mutual inductor consists of two coils X and Y as shown
in figure in which one-
quarter of the magnetic
with Y, giving a mutual
Y
inductance M. What will
be the mutual inductance when Y is used as the primary?
(a) M/4
(b) M/2
(c) M
(d) 2M
12
750The average induced emf in the circuit
is
( mathbf{A} cdot 0.2 V )
B. ( 0.1 V )
( mathbf{c} cdot 1 V )
D. ( 10 V )
12
751In figure a wire perpendicular to a long straight wire is moving parallel to the later with speed ( boldsymbol{v}=mathbf{1 0 m} / boldsymbol{s} ) in the
direction of the current flowing in the
later. The current is ( 10 A ). What is the
magnitude of the potential difference between the ends of the moving wire?
A ( cdotleft(5 times 10^{-4}right) ln (10) V )
B ( cdotleft(7 times 10^{-4}right) ln (10) V )
( mathbf{c} cdotleft(2 times 10^{-4}right) ln (2) V )
D. ( left(2 times 10^{-5}right) ln (10) V )
12
752Assertion
The direction of induced emf is always
such as to oppose the change that causes it.
Reason
Conservation of energy applies to know the direction of induced emf.
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
753A circuit ( A B C D ) is held perpendicular
to the uniform magnetic field of ( boldsymbol{B}= )
( 5 times 10^{-2} T ) extending over the region
( P Q R S ) and directed into the plane of
the paper. The circuit is moving out of
the field at a uniform speed of ( 0.2 m s^{-1} )
for ( 1.5 s . ) During this time, the current in
the ( 5 Omega ) resistor is
( mathbf{A} cdot 0.6 m A ) from ( B ) to ( C )
B. ( 0.9 m A ) from ( B ) to ( C )
c. ( 0.9 m A ) from ( C ) and ( B )
D. ( 0.6 m A ) from ( C ) to ( B )
E. ( 0.8 m A ) from ( C ) to ( B )
12
754A cylindrical bar magnet is lying along the axis of a circular coil. If the magnet
is rotated about the axis of the coil then
A. emf will be induced in the coil
B. only induced current will be generate in the coil
c. no current will be induced in the coil
D. both emf and current will be induced in the coil
12
755An aircraft having a wingspan of ( 20.48 m ) flies due north at a speed of
( 40 m s^{-1} . ) If the vertical component of earth’s magnetic field at the place is ( 2 times 10^{-5} T, ) calculate the emf induced
between the ends of the wings.
12
756The value of time when the current
reverse its sign for the first time will be
A. T/2
B. T/4
c. ( T / 6 )
D. ( T / 8 )
12
757the self inductance of the primary coil.12
758A coil having ( n ) turns and resistance ( boldsymbol{R} ) ( Omega ) is connected with a galvanometer of
resistance ( 4 R Omega ). This combination is
moved in time ( t ) seconds from a
magnetic flux ( W_{1} ) to ( W_{2} ). The induced
current in the circuit is
A. ( -frac{W_{2}-W_{1}}{5 R n t} )
в. ( frac{nleft(W_{2}-W_{1}right)}{5 R t} )
c. ( -frac{left(W_{2}-W_{1}right)}{R n t} )
D. ( -frac{nleft(W_{2}-W_{1}right)}{R n t} )
12
759A magnet is dropped freely towards a
loop of copper wire as shown in figure.
The acceleration of magnet will be:
A. equal to 9
B. greater than gless than ( g )
c. less than ( g )
D. zero
12
760A conducting rod is moved with a
constant velocity ( v ) in a magnetic field. A potential difference appears across
the two ends
( mathbf{A} cdot ) if ( vec{v} | vec{l} )
B. if ( vec{v} | vec{B} )
c. if ( vec{l} mid vec{B} )
D. none of these
12
761TU) 1 MTC
, 1 W1lPold
The graph shows the variation in magnetic flux o(t) with
time through a coil. Which of the statements given below
is not correct?
(a) There is a change in the direction as well as magnitude
of the induced emf between B and D
(b) The magnitude of the induced emf is maximum
between B and C
(c) There is a change in the direction as well as magnitude
of induced emf between A and C
(d) The induced emf is zero at B
12
762When a rod of magnetic material size ( 10 c m times 0.5 c m times 0.2 c m ) is located in
magentic field of ( 0.5 times 10^{4} mathrm{A} / mathrm{m} ) then ( mathrm{a} )
magnetic moment of ( 5 A m^{2} ) is induced in it. Find out magnetic induction in rod.
12
763A magnet is moved towards a coil, first
quickly and then slowly. The induced
e.m.f. produced is:
A. Larger in first case
B. Smaller in first case
C. Equal in both cases
D. Larger or smaller, depending upon resistance of the coil
12
764Assertion
Lenz’s law violates the principle of conservation of energy.
Reason
Induced emf always opposes the change in magnetic flux responsible for
its production.
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
765In 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 ( cdot frac{2 b}{v} )
B. ( frac{2 a}{v} )
c. ( frac{(a+b)}{v} )
D. ( frac{2(a-b)}{v} )
12
uniformly distributed over its circumference is hanging by an
insulated thread with the help of a
small smooth ring (not rigidly fixed with bigger ring). A time varying
magnetic field ( B=B_{0} sin omega t ) is
switched on at ( t=0 ) and the ring is
released at the same time. The induced
EMF in loop at time ( t=2 pi / omega ) is:
A . 0
в. ( frac{B_{0} pi omega R^{2}}{2} )
( mathbf{c} cdot B_{0} pi omega R^{2} )
D. ( -frac{B_{0} pi omega R^{2}}{2} )
12
767( = )
0
0
0
12
768Two Circular cells can be arranged in any of the three following situations as shown in figure. Their mutual inductance will be Maximum in which
arrangement ?
( A cdot(A) )
B. (B)
( c cdot(c) )
D. Same in all conditions
12
769Generators uses the principle of to push electrons through
a wire.
A. electromagnetic induction
B. electromagnetic reduction
c. magnetoelectric conduction
D. electric induction
E. magnetic field contraction
12
770The conductor ( A D ) moves to the right in
a uniform magnetic field directed into the plane of the paper.
This question has multiple correct options
A. The free electron in ( A D ) will move toward ( A )
B. Dd will acquire a positive potential with respect to
c. ( A ) current will flow from ( A ) to ( D ) in ( A D ) in closed loop
D. The current in ( A D ) flows from lower to higher potential
12
771toppr ( t )
shown in figure. The graph of magnitude of induced emf in the coil is
represented by
( A )
B.
( c )
D.
12
772For the situation shown in the figure,
flux through the square loop is
( mathbf{A} cdotleft(frac{mu_{0} i a}{2 pi}right) ln left(frac{a}{2 a-b}right) )
B ( cdotleft(frac{mu_{0} i b}{2 pi}right) ln left(frac{a}{2 b-b}right) )
( left(frac{mu_{0} i b}{2 pi}right) ln left(frac{a}{b-a}right) )
( left(frac{mu_{0} i a}{2 pi}right) ln left(frac{2 a}{b-a}right) )
12
773A coil having 200 turns has a surface
area of ( 0.15 m^{2} . ) A magnetic field of
strength ( 0.2 T ) applied perpendicular to this changes to ( 0.6 mathrm{T} ) in ( 0.4 mathrm{s} ), then the induced emf in the coil is
A . 45
B. 30
c. 15
D. 60
12
774A square loop of side length ( a ) having ( n )
turns is kept in a horizontal plane. ( mathbf{A} ) uniform magnetic field ( B ) exists in vertical direction as shown in figure. Now, the loop is rotated with constant angular speed ( omega ) as shown below. Which of the following statement is correct?
( begin{array}{llllll}mathbf{X} & mathbf{X} & mathbf{X} & mathbf{X} & mathbf{X} & mathbf{X}end{array} )
A. Same emf is induced in both cases (i) and (ii)
B. Maximum emf is induced in case (i)
c. Emf induced in case
(ii) is more than (i)
D. No emf induced in case (ii)
12
775Electric charge is uniformly distributed along a long straight wire of a radius of 1 mm. The Charge per cm length of the wire is Q coulomb. Another cylindrical surface
of radius ( 50 mathrm{cm} ) and length ( 1 mathrm{m} ) symmetrically encloses the wire as shown in fig. The total flux passing through the cylindrical surface
is
A ( cdot frac{Q}{epsilon_{0}} )
в. ( frac{100 Q}{epsilon_{0}} )
c. ( frac{10 Q}{pi epsilon_{0}} )
D. ( frac{100 Q}{pi epsilon_{0}} )
12
776When the current through the electromagnet of a relay reaches a particular value
A. It breaks the circuit
B. It open the circuit by pulling in an iron contact
c. It closes the circuit by pulling in an iron contact
D. Both A or C
12
777In a coil of area ( 10 mathrm{cm}^{2} ) and 10 turns with
magnetic field directed perpendicular to the plane and is changing at the rate
of ( 10^{8} ) Gauss/second. The resistance of
the coil is ( 20 Omega ). The current in the coil
will be
A. ( 0.5 mathrm{A} )
B. 5A
( c . ) 50 A
D . ( 5 times 10^{8} A )
12
778Assertion: The induced emf and current
will be same in two identical loops of copper and aluminium, when rotated with same speed in the same magnetic field.
Reason: Mutual induction does not depend on the orientation of the coils.
A. Both Assertion and Reason are true and Reason is the correct explanation of Assertion
B. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
c. Assertion is true but Reason is false
D. Assertion and Reason both are false
12
779The self inductance of a straight conductor is.
A. zero
B. Infinity
c. Very large
D. Very small
12
780State Flemings right hand rule. For what purpose is it used?12
781X
X
X
13. A conducting wire frame is placed in a magnetic fiel
which is directed into the plane of the paper (figure). Th
magnetic field is increasing at a
constant rate. The directions of
induced currents in wires AB and X
CD are
(a) B to A and D to C
(b) A to B and C to D
x x x xь x
(c) A to B and D to C
(d) B to A and C to D
14. An equilateral triangular loop ADC having some resistance
X
xxxxx
xВx xx
X
Y
X
12
782Two identical inductance carry currents
that vary with time according to linear laws (as shown in figure). In which of
two inductance is the self induction
emf greater?
( A )
B. 2
( c . ) same
D. data are insufficient to decide
12
783Whenever, current is changed in a coil, an induced e.m.f. is produced in the same coil. This property of the coil is due to
A. mutual induction
B. eddy currents
c. self induction
D. hysteresis
12
784Two concentric and coplanar circular
coils have radii ( a ) and ( b(>>a) ) as
shown in figure. Resistance of the inner coil is ( R ) Current in the outer coil is
increased from 0 to ( i ), then find the total
charge circulating the inner coil :
( ^{text {A }} cdot frac{mu_{0} pi a^{2} i}{2 R b} )
в. ( frac{2 mu_{0} pi a^{2}}{2 R b} )
c. ( frac{mu_{0} pi a^{2} i}{4 R b} )
D. ( frac{mu_{0} pi a^{3} i}{4 R b} )
12
785toppr
capacitor ( C ) as shown in the figure.
Magnetic field ( B ) is into the plane.
Consider the following statements:
(i) Current in loop ( boldsymbol{A} boldsymbol{E} boldsymbol{F} boldsymbol{B} boldsymbol{A} ) is
anticlockwise.
(ii) Current in loop ( boldsymbol{A} boldsymbol{E} boldsymbol{F} boldsymbol{B} boldsymbol{A} ) is
clockwise
(iii) Current through the capacitor is
zero.
(iv) Energy stored in the capacitor is
( frac{1}{2} C B^{2} L^{2} V^{2} )
Which if the following options is
correct?
A. Statements (i) and (iii) are correct
B. Statements (ii) and (iv) are correct
c. Statements (i), (iii) and (iv) are correct
D. None of these
12
786Write a short note on:
1. Armature coil
2. Brushes
3. Commutator
4. Direct current
12
787A flat coil, ( C ) of ( n ) turn, area ( A ) and
resistance ( R ), is placed in a uniform
magnetic field of magnitude ( B ). The plane of the coil is initially perpendicular to ( B ). The coil is rotated by an angle ( theta ) about a diameter and
charge of amount ( Q ) flows through it. Choose the correct alternatives.
This question has multiple correct options
A ( cdot theta=90^{circ}, Q=(B A n / R) )
B . ( theta=180^{circ}, Q=(2 B A n / R) )
c. ( theta=180^{circ}, Q=0 )
12
788Fill in the blank.
Electromagnetic induction occurs in a
wire when a change occurs in
in wire.
A . current
B. intensity of the electric field
C . voltage applied
D. magnetic field intensity applied
E. resistance added to the wire
12
789The phenomenon in which an emf is induced in a conductor kept just by the side of another conductor through which varying current is passed is called
A. Magnetic effect
B. Electromagnetic induction
c. Photoelectric effect
D. Mechanical effect
12
790A circular metal plate of radius ( boldsymbol{R} ) is rotating with a uniform angular velocity ( omega ) with its plane perpendicular to a uniform magnetic field ( B ). Then the emf developed between the centre and the
rim of the plate is
A ( cdot pi omega B R^{2} )
B. ( omega B R^{2} )
( mathbf{c} cdot pi omega B R^{2} / 2 )
D. ( omega B R^{2} / 2 )
12
791A long solenoid having 200 turns per ( mathrm{cm} ) carries a current of ( 1.5 a m p . ) At the centre of it is placed a coil of 100 turns
of cross-sectional are ( 3.14 times 10^{-4} m^{2} )
having its axis parallel to the field produced by the solenoid. When the direction of current in the solenoid is
reversed within 0.05 sec, the induced
e.m.f. in the coil is
A. ( 0.48 V )
в. ( 0.048 V )
( begin{array}{ll}.0 .0048 V & V \ V V & 0.088end{array} )
D. ( 48 V )
12
792Two conducting rings of radii r and ( 2 r )
move in opposite directions with velocities ( 2 v ) and ( v ) respectively on a conducting surfaces S. There is a
uniform magnetic field of magnitude B
perpendicular to the plane of the rings. The potential difference between the
highest points of the two rings is?
( A cdot ) zero
B. 2rvB
c. 4 rv ( B )
D. 8rvB
12
793The magnetic flux through a circuit of resistance R changes by an amount ( Delta phi ) in time ( Delta t . ) Then the total quantity of electric charges ( Q ) that passes any point in the circuit during the time ( Delta t ) is represented by:
A ( cdot Q=frac{Delta phi}{R} )
в. ( Q=frac{Delta phi}{Delta t} )
c. ( Q=R cdot frac{Delta phi}{Delta t} )
D. ( Q=frac{1}{R} cdot frac{Delta phi}{Delta t} )
12
794The emf of a genetator is 12 V and its internal resistance is 1 K( Omega .0 mathrm{m} )
measuring its emf with a voltmeter of ( 5 K Omega ) the reading will be:-
A . ( 10 v )
B. 10 milli v
c. 1 milliv
( D cdot 1 v )
12
795The diagram below show a coil
connected to a centre zero
galvanometer ( G . ) The galvanometer
shows a deflection to the right when the
( N ) -pole of a powerful magnet is moved
to the right as shown. Does the direction of the current in the coil appear
clockwise or anticlockwise viewed from
this end ( A ? )
A. The direction of induced current at end ( A ) is anti clockwise
B. The direction of induced current at end ( A ) is clockwise
c. The direction of induced current at end ( A ) is firsts clockwise and then anticlockwise
D. The direction of induced current at end ( A ) cannot be determined
12
796The coefficient of self induction of two
inductor coils are ( 20 m H ) and ( 40 m H )
respectively. If the coils are connected
in series so as to support each other and the resultant inductance is ( 80 m H )
then the value of mutual inductance
between the coils will be
( mathbf{A} cdot 5 m H )
в. ( 10 m H )
c. ( 20 m H )
D. ( 40 m H )
12
797The law of electromagnetic induction has been used in the construction of
A. Generator
B. Electric motor
c. Galvanometer
D. None of these
12
798Show the variation of the emf generated
versus time as the armature is rotated
with respect to the direction of the
magnetic field.
12
799Starter is used in
A. high power electric motors
B. low power electric motors
C. transformers
D. galvanometer
12
800An electromagnetic wave has energy in
the form of
A. variable electric field
B. variable magnetic field
c. both A and B
D. none of the above
12
801The coefficients of self induction of two
inductance coils arc ( 0.01 mathrm{H} ) and ( 0.03 mathrm{H} )
respectively. When they are connected in series so as to support each other then the resultant self inductance
becomes 0.06 Henry. The value of coefficient of mutual induction will be-
A . ( 0.02 mathrm{H} )
B. 0.05
c. ( 0.01 mathrm{H} )
D. ZERO
12
802A circular loop of radius ( r, ) having ( N )
turns of a wire, is placed in a uniform
and constant magnetic field ( boldsymbol{B} ). The
normal loop makes an angle ( theta ) with the
magnetic field. Its normal rotates with an angular velocity ( omega ) such that the angle ( theta ) is constant. Choose the correct
statement from the following. This question has multiple correct options
A . emf in the loop is ( N B omega r^{2} / 2 cos theta )
B. emf induced in the loop is zero
c. emf must be induced as the loop crosses magnetic lines
D. emf must not be induced as flux does not change with time
12
803A straight wire with a resistance of ( r )
per unit length is bent to form an angle
2 ( alpha ). A rod of the same wire
perpendicular to the angle bisector (of
( 2 alpha) ) forms a closed triangular loop. This loop is placed in a uniform magnetic
field of a induction ( B ). Calculate the
current in the wires when the rod moves
at a constant speed ( V )
12
804An average emf of ( 20 mathrm{V} ) is induced in an
inductor when the current in it is
changed from ( 2.5 A ) in one direction to the same value in the opposite direction in 0.1 s. The self-inuctance of
the inductor is
A . zero
в. ( 0.2 H )
( c .0 .4 H )
D. ( 1 H )
12
80533. In the circuit shown in figure, a A H
conducting wire HE is moved
with a constant speed y toward R V
>=0
left. The complete circuit is
placed in a uniform magnetic
field B perpendicular to the plane of the circuit inward.
The current in HKDE is
(a) clockwise
(b) anticlock wise
(c) alternating
(d) zero
12
806Which rule gives the direction of induced current due to electromagnetic induction?
A. Fleming’s left hand rule
B. Maxwell’s left hand rule
c. Ampere’s rule
D. Fleming’s right hand rule
12
807The flux of magnetic field through closed conducting loop of resistance 0.4 Whanges with time according to the
equation ( phi=0.20 t^{2}+0.40 t+0.60 ) where
is time in seconds. Find
(i) the induced
emf at ( t=2 s . ) (ii) the average induced emf in ( t=0 ) to ( t=5 ) s. (iii) change passed through the loop in ( t=0 ) to ( t=5 s . ) (iv) average current in time interval ( t=0 ) to
( t=5 s )
(v) heat produced in ( t=0 ) to ( t=5 s )
12
808A long wire carries a current ( i . ) A rod of
length ( l ) is moved with a velocity ( v ) in a
direction parallel to the wire as shown in figure (a). Find the motional emf induced in the rod:
A ( cdot frac{mu_{0} i}{2 pi x} l v )
В ( cdot frac{mu_{0} i}{2 pi} v log _{e} frac{x+l / 2}{x-l / 2} )
C ( frac{mu_{0} i}{2 pi} v log _{e} frac{x-l / 2}{x+l / 2} )
D. ( frac{mu_{0} i v}{2 pi} log _{e} frac{l+x}{x} )
12
809No. of magnetic lines of force present per unit volume is called
A. Magnetic flux
B. Magnetic line of force
c. Magnetic Induction
D. None of these
12
810The current produced in a closed coil, where magnetic lines of force rapidly change within it is called:
A. direct current
B. alternating current
c. induced current
D. none of these
12
811Two coils ( A ) and ( B ) have mutual
inductance ( 2 times 10^{-2} ) henry. If the
current in the primary is ( i= )
( 5 sin (10 pi t) ) then the maximum value of
e.m.f. induced in coil ( B ) is
( mathbf{A} cdot pi ) volt
в. ( frac{pi}{2} ) volt
c. ( frac{pi}{3} ) volt
D. ( frac{pi}{4} ) volt
12
812The device used for producing electric current is called a:
A. generator.
B. galvanometer.
c. ammeter.
D. motor
12
813A jet plane is travelling towards west at a speed of ( 1800 mathrm{km} / mathrm{h} ). What is the
voltage difference developed between the ends of the wing having a span of ( 25 m, ) if the Earth’s magnetic field at the location has a magnitude of ( 5 times )
( 10^{-4} T ) and the dip angle is ( 30^{circ} )
( begin{array}{ll}text { A } & text { 0.31 }end{array} )
в. 3.1
( c cdot 5 v )
D. 10
12
814Two coils have mutual inductance
( 0.005 H . ) The current changes in the form coil according to equation, ( boldsymbol{I}= )
( I_{0} sin omega t . ) Where ( I_{0}=10 A . ) and ( omega= )
( 100 pi ) rads/s. The maximum value of
emf in the second coil is :
A . ( 12 pi )
B. ( 8 pi )
( c .5 pi )
D. ( 2 pi )
12
815Principle behind the working of electric
generator?
A. When a conductor is moved in a magnetic field then voltage is induced in the conductor
B. When a conductor is moved in a magnetic field then current is induced in the conductor
( c cdot ) both
D. none
12
816The length of side of a square coil is 50 ( mathrm{cm} ) and number of turns in it is ( 100 . ) If it
is placed at right angles to a magnetic field which is changing at the rate of 4 Tesla/s, then induced emf in the coil will
be:
A . ( 0.1 mathrm{v} )
B. 1.0
( c cdot 10 v )
D. 100
12
817The equivalent inductance of two inductor is ( 2.4 m H ) when connected in
parallel and ( 10 m H ) when connected in
series. The difference between two
inductance is (neglecting mutual induction between coils)
( mathbf{A} cdot 3 m H )
в. ( 2 m H )
( mathrm{c} .4 mathrm{mH} )
D. ( 16 m H )
12
818s nucuct
length ( L=2 m, ) and a resistance ( r= )
( 10 Omega ) is moving with velocity ( v= )
( (2 m / s) hat{i} . ) Three mutually perpendicular
sides are parallel to ( x, y ) and ( z ) axis as
shown in figure. The corner A lies
at origin at ( t=0 . ) There is a magnetic
field in the region ( (mathbf{0} leq boldsymbol{x} leq boldsymbol{L}) ) is ( overrightarrow{boldsymbol{B}}= )
( (-5 hat{k}) T ) and ( B=0, ) otherwise. Which
of the following is correct?
A. current through ( b c ) is ( 2 A ) at ( t=0.25 s )
B. current through ( f g ) is ( 1 A ) at ( t=0.25 s )
C. potential difference across ( g h ) is ( 20 V ) at ( t=0.25 s )
D. potential difference across ( d h ) is ( 5 V ) at ( t=0.25 s )
E. potential difference across ( d h ) is ( 10 V ) at ( t=0.25 )
12
819x
x
В x
9. A conducting U-tube can A x x x
slide inside another as shown X
in the figure maintaining
electrical contacts between X
the tubes. The magnetic field
X
B is perpendicular to the B X X Y C
plane of the figure. If each
tube moves towards the other at a constant speed v, then
the emf induced in the circuit in terms of B, 1, and v, where
I is the width of each tube, will be
(a) 2Bly
(b) zero
(c) – Blv
(d) Blv (AIEEE 2005)
10 The calf indiretonne of the motor of an electrin fon in
12
820As shown in the figure, a rectangular loop of a conducting wire is moving away with a constant velocity ‘v’ in a perpendicular direction from a very long straight conductor a steady conductor carrying a steady current ‘I’. When the breadth of the rectangular loop is very small compared to its distance from the straight conductor.
( A )
[
E propto frac{1}{t^{2}}
]
в. ( quad E propto frac{1}{t} )
c. ( E propto ln (t) )
D.
[
E propto frac{1}{t^{3}}
]
12
821A conductor is moved in a varying magnetic field. Name the law which determines the direction of current
induced in the conductor:
A. Fleming’s right hand rule
B. Mohr’s right hand rule
c. Fleming’s left hand rule
D. Mohr’s left hand rule
12
822Define the term ‘self-inductance’ of a
coil. Write its S.I. unit.
12
823A rectangular coil having 60 turns and area of ( 0.4 m^{2} ) is held at right angles to a uniform magnetic field of flux density
( mathbf{5} times mathbf{1 0}^{-5} mathbf{T} . ) Calculate the magnetic flux
passing through it.
12
824A circular copper disc ( 10 mathrm{cm} ) in diameter rotates at 1800 revolution per minute about an axis through its centre and at right angles to disc. A uniform
field of induction ( B ) of 1 Wh ( m^{2} ) is
perpendicular to disc. What potential difference is developed between the axis of the disc and the rim?
A. 0.023 v v vas
B. 0.23
( c cdot 23 v )
D. 230 V
12
825What is the working principle of
generator?
A. Attractive property of magnets.
B. Conductors carrying current behave like magnets.
C. Electromagnetic induction.
D. none of the above
12
826Comment on the statement given below:
In self-induction

When the current in a coil is increasing, induced emf opposes it
When the current in a coil is
decreasing, induced emf supports it
A. A is true, B is false
B. A and B are false
c. A and B are true
D. A is false, B is true

12
827When the number of turns in a solenoid
is doubled without any change in the length of the solenoid, its selfinductance becomes:
A . Half
B. Double
c. Four times
D. Eight times
12
828toppr
perpendicular to the plane of the
triangle. The base of the triangle AB has
a resistance ( 1 Omega ) while the other two
sides have resistance ( 2 Omega ) each. The
magnitude of potential difference between the points ( A ) and ( B ) will be
( 4 cdot 0.4 )
( (mathrm{A}) )
8. 0.6 v
( (mathrm{B}) )
c. ( 1.2 v )
( (C) )
D. Non
( (mathrm{D}) )
12
829The figure shows a particle ( carrying change ( +q ) ) at the origin. A uniform magnetic field is directed into the plane of the paper. The particle can be projected only in the plane of paper and along positive or negative ( x ) -or ( y ) -axis. The particle moves with constant speed and has to hit target located in the third quadrant. There are two direction of projections, which can make it possible, these are then
( A cdot+x ) and ( +y )
B. ( +x ) and ( -y )
( c .-x ) and ( +y )
D. – x and – y
12
83038. A thin non-conducting ring of mass m carrying a charge
Q can freely rotate about its axis. Initially, the ring is
rest and no magnetic field is present. Then a uniform
field of magnetic induction was switched on, which was
perpendicular to the plane of the ring and increased with
time as a given function B(t). The angular velocity o(t)
of the ring as a function of the field B(t) will be given by
(a) 0(t) = 9B(t)
(b) m(t) = qB(t)
m
2m
(c)
(t) = 9B(1)
(d) 0=0
2nm
30 Anomf coco
12
831A dynamo dissipate 25 W when it supplies a current of 5 A through it. If the potential difference is 220
( v, ) then the emf produced is
A. ( 210 V )
B. ( 225 V )
( mathbf{c} cdot 230 V )
D. ( 235 V )
12
832An emf can be induced between the two
ends of straight copper wire when it is moved through a uniform magnetic field.
A. True
B. False
12
833A solenoid of 500 turns, diameter ( 20 c m )
and resistance ( 2 Omega ) is rotated about its
vertical diameter through ( pi ) radian in
( 1 / 4 ) s, when a horizontal field of ( 3 x )
( 10^{-5} T ) acts normal to its plane. Find the
emf induced and current thereof
12
834The induced EMF in loop at time ( t= )
( 2 pi / omega ) is :
( A cdot O )
B. ( frac{B_{0} pi omega R^{2}}{2} )
( mathbf{c} cdot B_{0} pi omega R^{2} )
D. ( -frac{B_{0} pi omega R^{2}}{2} )
12
835A coil is needed to operate an arc lamp of ( 150 mathrm{V}, 50 mathrm{Hz} ). The lamp of resistance of 5 ohms when running at 10 A. Find inductance of the choke coil, if the
same arc lamp is to be operated on 160 V, DC. What is the additional resistance
required?
A . ( 5 Omega )
B. ( 4.5 Omega )
c. ( 5.5 Omega )
D. 2.5Omega
12
836uan
10. A plane loop, shaped as two squares of sides a = 1 m and
b=0.4 m is introduced into
a uniform magnetic field I
to the plane of loop
(figure). The magnetic field
varies as B= 10-sin(100t)
T. The amplitude of the
current induced in the loop
if its resistance per unit length is r= 5 m 2 m is
(a) 2 A
(b) 3A
(c) 4A
(d) 5 A
11. A long conducting wire AH is moved over a conductina
12
837Magnetic flux during time interval ( tau ) varies through a stationary loop of
resistance ( boldsymbol{R}, ) as ( boldsymbol{phi}_{boldsymbol{B}}=boldsymbol{a} boldsymbol{t}(boldsymbol{tau}-boldsymbol{t}) . ) Find
the amount of heat generated during
that time. Neglect the inductance of the
loop.
( ^{text {A }} cdot frac{a^{2} tau^{3}}{R} )
в. ( frac{a^{2} tau^{2}}{2 R} )
c. ( frac{a^{2} tau^{3}}{3 R} )
D. ( frac{a^{2} tau^{3}}{4 R} )
12
838The induced emf produced when a magnet is inserted into a coil does not
depend upon:
A. The number of turns in the coil
B. The resistance of the coil
D. All the above
12
839An induced e.m.f. is produced when a
magnet is plunged into a coil. The strength of the induced e.m.f. is independent of
A. the strength of the magnet
B. number of turns of coil
c. the resistivity of the wire of the coil
D. speed with which the magnet is moved
12
840The magnetic flux density ( B ) is changing in magnitude at a constant
rate ( d B / d t . ) A given mass ( m ) of copper
drawn into a wire of radius ( a ) and
formed into a circular loop of radius ( r ) is
placed perpendicular to the field ( B ). The induced current in the loop is ( i . ) The resistivity of copper is ( rho ) and density is
d. The value of the induced current ( i ) is
( ^{mathbf{A}} cdot frac{m}{2 pi rho d} frac{d B}{d t} )
В. ( frac{m}{2 pi a^{2} d} frac{d B}{d t} )
c. ( frac{m}{4 pi a d} frac{d B}{d t} )
D. ( frac{m}{4 pi rho d} frac{d B}{d t} )
12
841Some physical quantities are given in list 1. The related units are given in list
2. Match the correct pairs
List 1 List 2
a) Magnetic Field Intensity ( W b m^{-1} )
e)
) Magnetic Flux f) ( W b m^{-2} )
b)
c Potential Magnetic ( W b )
c) g)
h) ( A m^{-1} )
d) Magnetic Induction
A. ( a-e, b-f, c-g, d-h )
B. a-h, b-g, c-e, d-f
c. a-h, b-e, c-g, d-f
D. a-f, b-g, c-e, d-h
12
842The induced emf in the smaller loop is
( A )
B.
( ^{mathbf{c}} cdot frac{_{3 mu_{0} pi i} R^{2} r_{r}^{2}}{2} )
( D )
E . none
12
843A circular disc of radius 0.2 meter is
placed in a uniform magnetic field of induction ( frac{1}{pi}left(W b / m^{2}right) ) in such way that
its axis makes an angle of ( 60^{circ} ) with ( vec{B} ). The magnetic flux linked with the disc is
A. ( 0.08 mathrm{wb} )
B. 0.01 Wb
c. ( 0.02 mathrm{wb} )
D. ( 0.06 mathrm{wb} )
12
844Two coils have a mutual inductance
( 0.005 H . ) The current changes in the first coil according to the equation ( i= )
( i_{m} sin omega t ) where ( i_{m}=10 A ) and ( omega= )
( 100 pi ) rad ( s^{-1} . ) The maximum value of
the emf induced in the second coil is
A ( .2 pi )
в. ( 5 pi )
c. ( pi )
D. ( 4 pi )
12
845The coefficient of mutual inductance
between two coils depends on
A. medium between the coils
B. separation between the two coils
c. orientation of the two coils
D. all of the above
12
846A metal conductor of length ( 1 mathrm{m} ) rotates vertically about one of its ends at angular velocity 5 radians per second. If
the horizontal component of earth’s magnetic field is ( 0.2 times 10^{-4} T ), then the
e.m.f developed between the two ends of
the conductor is
( A cdot 5 m v )
B. ( 50 mu V )
c. ( 5 mu V )
D. 50 mv
12
847Back emf of a cell is due to
A. Electrolytic polarization
B. Peltier effect
c. Magnetic effect of current
D. Internal resistance
12
848A magnet is allowed to fall through a copper circular wire. Then during fall:
A. the electric current flows through the wire
B. the acceleration of magnet is less than gravitational acceleration
c. the acceleration of magnet is equal to gravitational acceleration
D. the acceleration of magnet is greater than gravitational acceleration
12
849The armature of a dc motor has ( 15 Omega )
resistance. It draws a current of ( 1.6 mathrm{A} ) when run by 220 V de supply. The value of back emf will be:
A. 24
B. ( 196 v )
c. ( 220 v )
D. 244 V
12
850If a magnetic field ( B ) points in the
positive x direction, what is the magnitude of the emf developed in the
wire when ( B ) increases at the rate of ( 3 m )
( boldsymbol{T} boldsymbol{s}^{-1} ? )
12
852In the circuit shown here,cells ( A ) and ( B )
have emf ( 10 V ) each and the internal
resistance is ( 5 Omega ) for ( A ) and ( 3 Omega ) for ( B ). For
what value of ( R ) will the potential difference across the cell A will be zero?
A . 0
B. 1 ohm
c. 2 ohm
D. 3 ohm
12
853A magnetic flux of ( 500 mu W b )
passing through a 200 turns coil is
reversed in ( 20 times 10^{-3} ) seconds. The
average emf per unit area induced in
the coil in ( V / m^{2} ) is
A . 2.5
B. 5.0
( c .7 .5 )
D. 10.0
12
854State one point of similarity and one point of difference between an A.C. generator ans a D.C. motor.12
855Dynamos is a device that
A. reduces electric power
B. generates electricity
c. step down the voltage
D. the voltage
12
856A vertical ring of radius ( r ) and
resistance ( boldsymbol{R} ) falls vertically. lt is in
contact with two vertical rails which are
joined at the top. The rails are without friction and resistance. There is a
horizontal uniform magnetic field of
magnitude ( B ) perpendicular to the
plane of the ring and the rails. When the
speed of the ring is ( v, ) the current in the top horizontal of the rail section is
A . 0
B. ( frac{2 B r v}{R} )
( ^{mathrm{c}} cdot frac{4 B r v}{R} )
D. ( frac{8 B r v}{R} )
12
857A current of 1 A through a coil of inductance of ( 200 mathrm{mH} ) is increasing at
a rate of ( 0.5 mathrm{A} s^{-1} ). The energy stored in
the inductor per second is then
A. 0.5 J ( s^{-1} )
B. 5.0 Js ( ^{-1} )
c. ( 0.1 mathrm{Js}^{-1} )
D. 2.0 Js ( ^{-1} )
12
858op
( Q ) туре your question
generated across the coil during on
eycle is
12
859The value of magnetic field induction which is uniform, is 2T. What is the flux
passing through a surface of area
( 1.5 m^{2} ) perpendicular to the field.
A. 3 Tesla
В ( cdot 1 W b / m^{2} )
c. 2 Tesla
D. None
12
860An electron moves on a straight line path XY as shown. The abcd is a coil
adjacent to the path of electron. What will be the direction of current, if any,
induced in the coil?
A. No current induced
B. abcd
D. The current will reverse its direction as the electron
goes past the
12
861A helicopter rises vertically with a speed of ( 100 mathrm{m} / mathrm{s} ). If helicopter has length ( 10 mathrm{m} ) and horizontal component
of earth’s magnetic field is ( 5 times )
( 10^{-3} W b / m^{2}, ) then the induced emf
between the tip of nose and tail of helicopter is:
A. ( 50 v )
B. 0.5 ( v )
( c cdot 5 v )
D. 25 V
12
862Which rule determines the direction of
current induced in a coil due to the
rotation in a magnetic field.
A. Maxwell right hand grip rule
B. Fleming’s left hand rule
c. Fleming’s right hand rule
D. None
12
863An emf of 100 millivolts is induced in a
coil when the current in another nearby coil becomes ( 10 A ) from zero to 0.1 sec
The corfficient of mutual induction
between the two coils will be
( mathbf{A} cdot 1 m H )
в. ( 10 mathrm{mH} )
c. ( 100 mathrm{mH} )
D. ( 1000 m H )
12
864Figure shows a rectangular conductor PQRS in which the Conductor PQ is free
to move in a uniform magnetic field
perpendicular to the plane of the paper. The filed extends from ( x=0 ) to ( x=b ) and is
zero for ( x>b ). Assume that only the arm
PQ possesses resistance r. when the
( operatorname{arm} ) PQ is pulled outward from ( x=0 ) to
( x=2 b ) and is then moved back to ( x=0 )
with constant speed ( v, ) Determine the expression for the flux and induced emf
Sketch the variations of these
quantities with distance ( 0 leq x leq 2 b )
12
865A conducting loop in the form of a circle is placed in a uniform magnetic field with its plane perpendicular to the direction of the field. An e.m.f. will be
induced in the loop if This question has multiple correct options
A . I is translated parallel to itself
B. It is rotated about one of its diameters.
c. It is rotated about its own axis which is parallel to the field
D. The loop is deformed from the original shape
12
866A conducting circular loop is placed in a uniform magnetic field, ( B=.025 ) T with its plane perpendicular to the loop. The
constant rate of ( 1 mathrm{mm} ) s1. The induced
e.m.f. when the radius is ( 2 mathrm{cm} ), is
( A cdot 2 mu V )
в. ( 2 pi mu V )
( c . pi mu V )
D ( cdot frac{pi}{2} mu V )
12
867The figure shows a part of an electric
circuit. The wires ( A B, C D ) and ( E F ) are long
and have identical resistances. The
separation between the neighboring
wires is ( 1.0 mathrm{cm} ). The wires EA and BF have
negligible resistance and the ammeter
reads 30 A. Calculate the magnetic force
per unit length on ( A B ) and ( C D )
12
868A closed circuit consists of a resistor ( boldsymbol{R} ) inductor of inductance ( L ) and a source
of emf ( boldsymbol{E} ) are connected in series. If the
inductance of the coil is abruptly
decreased to ( L / 4 ) (by removing its magnetic core), the new current immediately after this moment is :
(before decreasing the inductance the circuit is in steady state)
A. Zero
B. ( frac{E}{R} )
( c cdot 4 frac{E}{R} )
D. ( frac{E}{4 B} )
12
869Read the following statements and answer whether the given statement is true or false.
Lenz’s law is used to find out the
magnitude of the induced e.m.f.
A. True
B. False
12
870The rate of change of magnetic flux density through a circular coil of area 10
( mathrm{m} ) and number of turns 100 is ( 10^{3} mathrm{Wb} / mathrm{m} )
2 /s. The value of induced emf will be
( A cdot 10^{-2} v )
B. ( 10^{-3} v )
( c cdot 10 v )
( D cdot 10^{6} v )
12
8718. A square loop of side 5 cm enters a magnetic field with
1 cms-1. The front edge enters the magnetic field at t=0
then which graph best depicts emf
5 cm
*
*
*
*
*
*
B=0.6T
20 cm –
3×10
0
5
15
20
– 3×10
20
t(s)
0
5
3 x 10
(c)
15 2015)
3 x 10
(d)
15 20t(s)
ol
12
872The phenomenon of electromagnetic induction was discovered by
A . Lenz
B. Maxwell
c. Fleming
12
873Two conducting rings of radii r and 2 r move in opposite directions with
velocities ( 2 v ) and ( v ) respectively on a
conducting surface ( S ). There is a
uniform magnetic field of magnitude ( B ) perpendicular to the plane of the rings. The potential difference between the highest points of the two rings is
A . zero
в. ( 2 r v B )
( mathbf{c} cdot 4 r v B )
D. ( 8 r v B )
12
induction and obtain an expression of induced e.m.f.
12
875t is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet. A small flat search coil of area ( 2 mathrm{cm}^{2} ) with 25 closely
wound turns, is positioned normal to the field direction, and then quickly snatched out of the field region.
Equivalently, one can give it a quick ( 90^{circ} )
turn to bring its plane parallel to the field direction). The total charge flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5
mC. The combined resistance of the coil
and the galvanometer is ( 0.50 Omega ) Estimate the field strength of magnet.
12
876A conducting wire in the form of circular loop of radius ( sqrt{frac{2}{pi}} mathrm{m} ) is places normal to a uniform magnetic field of induction 2T. If the magnetic induction is uniformly reduced to T in 2s, the induced e.m.f in the loop is
A. 4 volt
B. 2volt
c. 1 volt
D. 0.4volt
12
877A uniform magnetic field of induction ( mathrm{B} )
is confined to a cylindrical region of
radius R. The magnetic field is
increasing at a constant rate of ( frac{d B}{d t} T s^{-1} . ) An electron of charge ( e ) placed at the point ( P ) on the periphery of the field experiences an acceleration
A ( cdot frac{1}{2} frac{e R}{m} frac{d B}{d t} ) toward left
B. ( frac{1}{2} frac{e R}{m} frac{d B}{d t} ) toward right
c. ( frac{e R}{m} frac{d B}{d t} ) toward left
D. zero
12
878Deduce an equation ( U=frac{1}{2} L I^{2} ) for an
inductor.
12
879The self induction of a coil having 400 turns is ( 10 mathrm{mH} ). The magnetic flux through the cross section of the coil corresponding to current ( 2 mathrm{mA} ) is :
A ( cdot 2 times 10^{-5} mathrm{Wb} )
В. ( 8 times 10^{-3} mathrm{Wb} )
c. ( 4.3 times 10^{-5} mathrm{Wb} )
D. ( 4.8 times 10^{-3} mathrm{Wb} )
12
880A rectangular coil of area ( A ), having the
number of turns ( N ) is rotated at ( f )
revolutions per second in a uniform
magnetic field ( B ) the field is perpendicular to the coil. Prove that the maximum emf induced in the coil is
( 2 pi f N B A )
12
881What is the source of energy associated with the current obtained in part when a
magnet is moved towards a coil having a galvanometer at its ends?
12
882When a current of 5 A flows in the
primary coil then the flux linked with the secondary coil is 200 weber. The value of coefficient of mutual induction
will be
A . 1000 н
в. 40
c. ( 195 mathrm{H} )
D. 205 H
12
883A coil of inductance ( 5 mathrm{H} ) is joined to a
cell of emf ( 6 mathrm{V} ) through a resistance ( 10 Omega ) at time ( t=0 . ) The EMF across the coil at
time ( t=ln sqrt{2} s ) is:
( A cdot 3 v )
B. 1.5
c. ( 0.75 v )
D. 4.5
12
884Fig shown below represents an area
( A=0.5 m^{2} ) situated in a uniform
magnetic field ( B=2.0 w e b e r / m^{2} ) and
making an angle of ( 60^{circ} ) with respect to
magnetic field. The value of the
magnetic flux through the area would be equal to:
A. 2.0 weber
B. ( sqrt{3} )weber
c. ( sqrt{3} / 2 ) weber
D. 0.5 weber
12
885A coil of area ( A_{0} ) is lying in such a magnetic field whose value changes
from ( B_{0} ) to ( 4 B_{0} )
in ( t ) seconds. The induced emf in the coil
will be :
A ( cdot frac{4 B_{0}}{A_{0} t} )
в. ( frac{4 B_{0} A_{0}}{t} )
c. ( frac{3 B_{0} A_{0}}{t} )
D. ( frac{3 B_{0}}{A_{0} t} )
12
886In given diagrams write the direction of
magnetic field produced at point ( boldsymbol{P} ) in
form of ( otimes ) and ( odot )
12
887Which of the following are not units of
self inductance?
This question has multiple correct options
A. Weber / m ( ^{2} )
B. ( O h m- )second
c. Joule – ampere
D. Joule – ampere ( ^{-} )
12
888Derive expression for the self-induction of solenoid. What factors affect its value
and how?
12
88968. In Figures (a) and (b), two air-cored solenoids P and o
have been shown. They are placed near each other. In
Figure (a), when Ip, the current in P, changes at the rate
of 5 As), an emf of 2 mV is induced in Q. The current in
P is then switched off, and the current changing at 2 AS!
is fed through as shown in the figure. What emf will be
induced in P?
(a)
(a) 8 x 10-4 v
(c) 5 x 10-3v
(b)
(b) 2 x 10-V
(d) 8 x 10-20
U
m
bollow cold as shown
12
890In a coil of resistance ( 10 Omega ), the induced
current developed by changing magnetic flux through it, is shown in figure as a function of time. The magnitude of change in flux through the coil in Weber is-
12
891Find the approximate value of induced
current assuming the resistance to the current is confined to the square.
A ( cdot frac{B L omega d t}{rho} )
( ^{text {В }} cdot frac{B L^{2} omega d t}{rho} )
( ^{text {c. }} frac{B L^{2} omega d}{rho} )
( frac{B L omega d^{2}}{rho} )
12
892If radius of long solenoid is doubled, then its self inductance will be :
A. same
B. doubled
c. trippled
12
893A conducting wheel rim in which there
we three conducting rods of each of
length ( l ) is rotating with constant
angular velocity ( omega ) in a uniform
magnetic field Bas show in figure. The
induced potential difference between
its centre and rim will be :
( mathbf{A} cdot B omega l^{2} )
B. ( frac{3}{2} B omega l^{2} )
c. 0
D. ( frac{B omega l^{2}}{2} )
12
894X
X
X
26. A conducting ring of radius r X X X X
is rolling without slipping with
a constant angular velocity o
(figure). If the magnetic field X
strength is B and is directed into
the page then the emf induced
across PQ is
X X X2x x
Bor2
(a) Bor?
(b)
X
X
π2,2 Βω
(c) 4Bor?
(d)
D:
odmorit
12
895The phenomenon of electromagnetic
induction is
A. the process of charging a sphere
B. the process of producing magnetic field in a coil
C. the process of producing induced current in a coil whenever there is a relative motion between the coil
and the magnet
D. the process of producing cooling effect
12
896A wire in the form of a circular loop of radius ( 10 mathrm{cm} ) lies in a plane normal to a
magnetic field of ( 100 T . ) If this wire is pulled to take a square shape in the same plane in ( 0.1 s, ) find the average induced emf in the loop.
( mathbf{A} cdot 8.99 V )
B. ( 4.33 V )
c. ( 7.77 V )
D. ( 6.74 V )
12
897toppr
( v_{0} . ) Which of the following graph truly depicts the variation of current through the conductor with time?
3
2
12
898Carbon brushes are not necessary in a
dynamo, if the coil remains stationary
and the magnet moves, because
A. Current is drawn from a stationary source
B. Current is drawn from a moving source
c. Direct current is produced
D. It is not necessary to reverse the direction of the current
12
899A magnet is moved towards the coil
(i) quickly in one case, and
(ii) slowly in another case.
Then the induced emf is :
A. larger in case (i)
B. smaller in case (i)
c. equal in both
D. larger or smaller depending upon the radius of the coil
12
9007. The figure shows four wire loops, with edge lengths of
either L or 2L. All four loops will move through a region
of uniform magnetic field B (directed out of the page) at
the same constant velocity. Rank the four loops according
to the maximum magnitude of the e.m.f. induced as they
move through the field, greatest first
(a) (x = £j)(&q=&)
(c) Ę > Ed > & > Ey (d) x < £; <& < En
12
infinitely long wire carrying a constant
current ( I . ) The sides ( P Q ) and ( R S ) are
parallel to the wire. The wire and the
loop are in the same plane. The loop is
rotated by ( 180^{circ} ) about an axis parallel to
the long wire and passing through the
mid-points of the sides ( Q R ) and ( P S . ) The
total amount of charge which passes through any point of the loop during
rotation is
A ( cdot frac{mu_{0} I a}{2 pi r} ln 2 )
B. ( frac{mu_{0} I a}{pi r} ln 2 )
c. ( frac{mu_{0} I a^{2}}{2 pi r} ln 2 )
D. cannot be found because time of rotation is not given
12
902The armature of a demonstrator
generator consists of a flat square coil
of side ( 4 c m ) and 200 turns. The coil
rotates in a magnetic field of 0.75 T. The
angular speed so that a maximum emf of ( 1.6 V ) is generated is:
A ( cdot frac{20}{3} ) rad/s
B. ( frac{10}{3} ) rotations/s
c. ( frac{40}{3} ) rpm
D. None of these
12
903If ( mathrm{N} ) is the number of turns in a coil, the
value of self-inductance varies are
( mathbf{A} cdot mathbf{N}^{mathbf{0}} )
B.
c. ( N^{2} )
( D cdot N^{-2} )
12
904As shown in the figure, ( P ) and ( Q ) are two coaxial conducting loops separated by
some distance. When the switch ( S ) is
closed, a clockwise current ( l_{p} ) flows in ( P )
(as seen by ( E ) ) and an induced current
( l_{Q 1} ) flows in ( Q . ) The switch remains
closed for a long time. When ( S ) is
opened, a current ( l_{Q 2} ) flows in ( Q ). Then
the direction ( l_{Q 1} ) and ( l_{Q 2}(text { as seen by } E) )
are
A. respectively clockwise and anti-clockwise
B. both clockwise
( c . ) both anti-clockwise
D. respectively anti-clockwise and clockwise
12
coll ana aırectea ınto the paper Is varying according to the relation ( phi= )
( 6 t^{2}+7 t+1, ) where ( phi ) is in milliweber
and ( t ) is in second. The magnitude of the
emf induced in the loop at ( t=2 s ) and
the direction of induce current through
( boldsymbol{R} ) are
8
A. 39 mV; right to left
B. 39 mV; left to right
c. ( 31 mathrm{mV} ; ) right to left
D. 31 mV; left to right
12
906A metallic wire bent into a right ( Delta ) abc
moves with a uniform velocity ( boldsymbol{v} ) as
shown in figure. B is the strength of
uniform magnetic field perpendicular
outwards the plane of triangle. The net
emf is …………….. and emf along ab is
A. zero, zero
B. zero, ( B v(b c) ) with ( b ) positive
C. zero, ( B v(b c) ) with ( a ) positive
D. ( B v(b c) ) with ( c ) positive, zero
E. ( B v(b c) ) with ( b ) positive, zero
12
907The magnetic flans associated with a metal ring varies with time all. to ( phi= ) ( mathbf{3}left(boldsymbol{a} boldsymbol{t}^{3}-boldsymbol{b} boldsymbol{t}^{2}right) boldsymbol{T} boldsymbol{m}^{2}, boldsymbol{a}=boldsymbol{2} boldsymbol{s} boldsymbol{e} boldsymbol{c}^{-3}, boldsymbol{b}= )
( 6 sec ^{-2} . ) If the resistance of the ring is
( 24 Omega, ) the current induced in the ring
during the time ( t=2 sec ) is
A. ( 2 a m p )
в. ( 4 a m p )
c. ( 6 a m p )
D. zero
12
908A rod of length ( l ) rotates with a uniform
angular velocity ( omega ) rad/s about an axis passing through its middle point but normal to its length in a uniform magnetic field of induction ( B )
with its direction parallel to the axis of rotation. The induced emf between the
two ends of the rod is :
( ^{A} cdot frac{B l^{2} omega}{2} )
в. zero
c. ( frac{B l^{2} omega}{4} )
D ( cdot 2 B l^{2} omega )
12
909A dynamo produces an electric current.
It is based on the principle:
A. magnets have attractive property
B. conductors carrying current behave like magnets
C. electromagnetic induction
D. none of these
12
910A coil of area ( 500 mathrm{cm}^{2} ) having 1000 turns
is placed such that the plane of the coil is perpendicular to a magnetic field of magnitude ( 4 times 10^{-5} ) weber ( / m^{2} ). If it is
rotated by 180 about an axis passing through one of its diameter in ( 0.1 mathrm{sec} ), find the average induced emf
A. zero
B. 30 mv
c. ( 40 mathrm{mv} )
D. 50 mv
12
911An e.m.f. of 5 millivolt is induced in a
coil when in a nearby placed another coil, the current changes by 5 ampere in
0.1 second. The coefficient of mutual
induction between the two coils will be :
A. 1 Henry
B. 0.1 Henry
c. 0.1 millihenry
D. 0.001 millihenry
12
912A conducting loop is held above a
current carrying wire ‘PQ’ as shown in the figure. Depict the direction of the
current induced in the loop when the current in the wire ( P Q ) is constantly
increasing.
12
913Match the following
Physical Quantity Unit in ¿uc is an a it ( begin{array}{l}text { a) Magnetic Moment } \ text { b) Magnetic Flux Density } \ text { c) Intensity of Magnetic Field } & text { e) } A m p-m \ text { d) Pole strength } & text { g) } N-m^{3} / W b \ text { h) Gauss }end{array} )
( A cdot a-e, b-f, c-g, d-h )
B. ( a-g, b-h, c-f, d-e )
( mathbf{C} cdot a-g, b-f, c-h, d-e )
D. a-e, b-f, c-h, d-g
12
914While travelling back to his residence in the car, Dr. Pathak was caught up in a thunderstorm. It became very dark. He stopped driving the car and waited for thunderstorm to stop. Suddenly he noticed a child walking alone on the road. He asked the boy to come inside the car till the thunderstorm stopped.
Dr. Pathak dropped the boy at his residence. The boy insisted that Dr. Pathak should meet his parents. The parents expressed their gratitude to Dr. Pathak for his concern for safety of the child.

Answer the following questions based on the above information:
(a) Why is it safer to sit inside a car during a thunderstorm?
(b) Which two values are displayed by
Dr. Pathak in his action?
(c) Which values are reflected in
parents’ response to Dr. Pathak?
(d) Give an example of similar action on your part from your everyday life?

12
915A uniform but time-varying magnetic
field ( B_{(t)} ) exists in a circular region of radius a and is direction into the plane
of the paper, as shown in the figure. The magnitude of the electric field at point ( P ) at a distance ( r ) from the centre of the
circular region
( A ). is zero
B. decreases as ( 1 / r )
c. increases as
D. decrease as ( 1 / r^{2} )
12
916Two circular loops lie side by side in the same plane. One is connected to a
source that supplies an increasing current, the other is a simple closed ring. Is the induced current in the ring is in the same direction as that in the loop connected to the source or opposite? What if the current in the first loop is
decreasing?
12
917Name two devices based on the
magnetic effect of electricity.
12
918A cylindrical bar magnet is kept along the axis of a circular coil. On rotating the magnet about its axis, the coil will
have induced in it
A . a current
B. no current
c. only an e.m.f.
D. both an e.m.f. and a current
12
919On what factors does the induced
electromotive force depend?
12
920Given below are the symbols of a few
electronic components. Which of these
components denote a variable inductor
7
( A )
B.
( c )
D.
12
921Generators used in power stations to
generate electricity are
A. DC generators
B. AC generators
( c cdot ) Both
D. None
12
922Two coils ( A ) and ( B ) have mutual
inductance ( 2 times 10^{-2} ) henry. If the
current in the primary is ( i= ) ( 5 sin (10 pi t) ) then the maximum value of
e.m.f. induced in coil B is:
A . pivolt
в. ( frac{pi}{2} ) volt
c. ( frac{pi}{3} ) volt
D. ( frac{pi}{4} ) volt
12
923Draw a labeled diagram of AC generator.Derive the expression for the instantaneous value of the emf induced
in the coil.
12
924A wheel of radius ( 2 mathrm{m} ) having 8 conducting concentric spokes is rotating about its geometrical axis with an angular velocity of 10 rad/s in a uniform magnetic field of ( 0.2 T ) perpendicular to its plane. The value of induced emf between the rim of the
wheel and centre is
A . 2
B. 6
( c cdot 4 )
D. 8
12
925The relation between ( [boldsymbol{E}] ) and ( [boldsymbol{B}] ) is
( mathbf{A} cdot[E]=[B][L][T] )
B . ( [E]=[B][L]^{-1}[T] )
c. ( [E]=[B][L][T]^{-1} )
D・ ( [E]=[B][L]^{-1}[T]^{-1} )
12
926The device used for producing current is
called a
12
927Assertion
Mutual inductance of a pair of coils depend on their separation as well as their relative orientation.
Reason
Mutual inductance depend upon the
length of the coil only.
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
928Explain the reasons for the following in
a power generator.
a.armature is used as stator.
b. Strong electromagnets are used as field magnet.
c. Three armature coil are arranged at
( 120^{circ} ) angular separation
12
929Which statement is incorrect related to
induced electric field due to changing magnetic flux?
A. It varies with time
B. It is non-conservative
c. It forms closed loop
D. Both (1) & (3)
12
930If circular coil with ( N_{1} ) turns is changed
in to a coil of ( N_{2} ) turns. What will be the
ratio of self inductances in both cases.
A ( cdot frac{N_{1}}{N_{2}} )
B. ( frac{N_{2}}{N_{1}} )
c. ( frac{N_{1}^{2}}{N_{2}^{2}} )
D. ( sqrt{frac{N_{1}}{N_{2}}} )
12
931When the number of turns in a coll is
doubled without any change in the length of the coll, its self-inductance
becomes
A. four times
B. Double
c. Halved
D. Not change
12
932A conducting loop is pulled outward
with a constant speed.

The induced emf between the point ( A ) and B, just after the motion start is

12
933A dynamo makes 100 cycles per second. The frequency of the AC is
A. ( 100 mathrm{Hz} )
в. 200 нz
c. 50 нz
D. 400 нz
12
934B
25. A wire of length 1. mass m, and resistance R slides without
any friction down the parallel conducting rails of negligible
resistance (figure). The
rails are connected to
each other at the bottom
by a resistanceless rail
parallel to the wire so
that the wire and the rails
form a closed rectangular
conducting loop. The
plane of the rails makes
an angle e with the
horizontal and a uniform
vertical magnetic field of
induction B exists throughout the region. Find the steady-
state velocity of the wire.
mg sine
mg sine
(a)
RB21² cos²6 RB²1² cos² e
sin e
°B212 cose
(c) mgr sine
(d) mg B-12 cose
12
935Mark the correct statement the
magnitude of current induced in the
coil can be increased
A. by winding the coil on a soft iron core
B. by increasing the number of turns in the coil.
c. by increasing the strength of magnett
D. all
12
936A straight copper wire is moved in a uniform magnetic field such that it cuts the magnetic lines of force. Then
A. emf will not be induced
B. emf will be induced
c. sometimes emf will be induced and sometimes not
D. nothing can be predicted
12
937Consider a current carrying coil placed in a magnetic field. What are the requirements for induced current to
flow as per electromagnetic induction
A . Coil of wire carrying current
B. Change in magnetic field associated with the coil
c. Both A and B
D. None
12
938In the space shown a non-uniform
magnetic field ( overrightarrow{boldsymbol{B}}=boldsymbol{B}_{0}(boldsymbol{1}+boldsymbol{x})(-boldsymbol{k}) )
tesla is present. A closed loop of small resistance, placed in the ( x ) -y plane is
given velocity ( V_{0} . ) The force due to
magnetic field on the loop is
A. zer
B. along + x direction
C. along ( -x ) direction
D. along +y direction
E. none of these
12
939Fill in the blanks.
Device that converts mechanical energy into electrical energy
is
12
940A uniform thin rod of length L is moving
in a uniform magnetic field ( B_{0} ) such
that velocity of its centre of mass is ( mathbf{v} ) and angular velocity is ( omega=frac{4 v}{L} ) Then
A. e.m.f. between end ( mathrm{P} ) and ( mathrm{Q} ) of the rod is ( B_{0} l v )
B. end P of the rod is at higher potential than end Q of the rod
C. end ( Q ) of the rod is at higher potential than end P of the rod
D. the electrostatic field induced in the rod has same direction at all points along the length of rod
12
941are used in making electric generators and electric motors.
A. electric current
B. magnetes
c. cables
D. all
12
942The magnetic flux through a loop is varying according to a relation ( phi= ) ( 6 t^{2}+7 t+1 ) where ( phi ) is in milliweber
and ( t ) is in second. What is the e.m.f.
induced in the loop at ( t=2 ) second?
12
943(d) UTOA
49. A long solenoid of length L, cross section A having
N, turns has wound about its center a small coil of N, turns
as shown in figure. The mutual inductance of two circuits is
—— – – – – – – – –
ba
(a)
MOA(N /N)
| (b) (NN)
L
(c) Ho AN,N2L
(2) MAN, ²N,
ANNI
12
944Assertion
In a varying magnetic field the induced currents exhibit diamagnetic-like repulsion effects. A conductive object
will experience a repulsion force.
Reason
Eddy currents produced in conductor will produce magnetic field to oppose the varying magnetic field according to faradays 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
945Define self inductance of a coil. Derive
the expression for magnetic energy stored in the inductor of inductance ( L )
carrying current ( boldsymbol{I} )
12
94648. The coefficient of mutual inductance of two circuits A and
B is 3 mH and their respective resistances are 10 and 412.
How much current should change in 0.02 s in circuit A,
so that the induced current in B should be 0.0060 A?
(a) 0.24 A
(b) 1.6 A
(c) 0.18 A
(d) 0.16 A
12
947A wheel with 4 spokes is placed with its
plane perpendicular to a uniform magnetic field B of magnitude 0.5 T. The field is directed into the plane of the paper and is present over the entire
region of the wheel as shown in fig. When the switch ( mathrm{S} ) is closed, there is
initial current of 6 A between the axis
and the rim and the wheel begins to rotate. Resistances of the spokes are 1
2,4 and ( 8 Omega, ) respectively. Resistance of rim is negligible
If current in ( 1 Omega ) is ( 2 / X ) A. Find ( X ? )
12
948A horizontal straight wire ( 10 mathrm{m} ) long extending from east to west is falling
with a speed of ( 5.0 m s^{-1}, ) at right angles
to the horizontal component of the
earth’s magnetic field 0.30 ( times 10^{-4} W B m^{-2} . ) (a) What is the
instantaneous value of the emf induced
in the wire?(b) What is the direction of
the emf?(c) Which end of the wire is at
the higher electrical potential?
12
949A small, conducting circular loop is placed inside a long solenoid carrying a current. The plane of the loop contains
the axis of the solenoid. If the current in
the solenoid is varied. The current
induced in the loop is
A. clockwise
B. anti-clockwise
c. zero
D. clockwise or anti-clockwise depending on whether the resistance is increased or decreased
12
950(a) What are the defects of eye? How are
these rectified?
(b) Observe the figure and answer the following questions:
(i) What does the given diagram
represent?
(ii) Write the principle of the device
denoted in the given diagram.
12
951Two identical coaxial coils ( P ) and ( Q )
carrying equal amount of current in the same direction are brought nearer. The
current in
A. ( P ) increases while in ( Q ) decreases
B. ( Q ) increases while in ( P ) decreases
c. Both ( P ) and ( Q ) increases
D. Both ( P ) and ( Q ) decreases
E. Both ( P ) and ( Q ) remains constant
12
952The length of a thin wire require to
manufacture a solenoid of length ( l= ) ( 100 mathrm{cm} ) and inductance ( L=1 m H, ) if
the solenoid’s cross-sectional diameter
is considerably less than its length is:
A. ( 1 k m )
в. ( 0.10 mathrm{km} )
c. ( 0.010 mathrm{km} )
D. ( 10 mathrm{km} )
12
953Draw the diagram of a DC dynamo and label the following parts:
a) Split rings
b) Armature coil
12
954A loop shown in the figure is immersed
in the varying magnetic field ( B=B_{0} t )
directed into the page. If the total
resistance of the loop is ( R ), then the
direction and magnitude of induced current in the inner circle is :
( ^{mathrm{A}} cdot_{mathrm{clockwise}} frac{B_{0}left(pi a^{2}-b^{2}right)}{R} )
B. anticlockwise ( frac{B_{0}left(pi a^{2}+b^{2}right)}{R} )
c. ( _{text {clockwise }} frac{B_{0}left(pi a^{2}+4 b^{2}right)}{R} )
” clockwise ( frac{B_{0}left(4 b^{2}-pi a^{2}right)}{R} )
12
955Two solenoids have identical
geometrical construction but one is made of thick wire and the other of thin
wire. Which of the following quantities are different for the two solenoids?
This question has multiple correct options
A. Self-inductance
B. Rate of Joule heating if the same current goes through them
c. Magnetic field energy if the same current goes through them
D. Time constant if one solenoid it connected to one battery and the other is connected to another battery
12
956When the acceleration of rod is zero, the
charge on capacitor is :
( ^{text {A. }} frac{B^{2} L^{2} C Q_{0}}{M+B^{2} L^{2} C} )
( ^{text {В }} frac{B^{2} R^{4} C^{3} Q_{0}}{M+B^{2} L^{2} C^{2}} )
c. ( frac{B^{2} R^{4} C^{3} Q_{0}}{M+B^{2} R^{4} C^{4}} )
D. ( frac{B^{2} L^{2} C Q_{0}}{M+B^{2} L^{2} C^{2}} )
12
957A coil with 100 turns has an inductance
of ( 0.05 H ) and ( 0.02 A ) current is passed
through it. Flux linked with the coil is
A ( cdot 10^{-2} W b )
В ( cdot 10^{-3} W b )
( mathbf{c} cdot 10^{-4} W b )
D. ( 10^{-5} W b )
12
958What do you mean by magnetic flux?12
959Assertion
An emf is induced in a long solenoid by
a bar magnet that moves while totally inside the solenoid along the axis of the
solenoid.
Reason
As the magnet moves inside the
solenoid the flux through individual turns of the solenoid changes.
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
960A metal rod moves at a constant
velocity in a direction perpendicular to its length. A constant uniform magnetic
field exists in space in a direction perpendicular to the rod as well its
velocity. Select correct statements from the following
A. the entire rod is at the same potential
B. there is an electric field in the rod
c. the electric potential is highest at the centre
D. the electric potential is lowest at its centre and increases towards its ends
12
961A solenoid has 2000 turns wound over a
length of ( 0.3 m . ) Its cross-sectional area is equal to ( 1.2 times 10^{-3} m^{2} ). Around its
central cross-section, a coil of 300
turns is wound. If an initial current of
( 2 A ) flowing in the solenoid is reversed in
( 0.25 s, ) the emf induced in the coil is
A ( .0 .6 m V )
B. ( 60 m V )
c. ( 40.2 m V )
D. ( 0.48 m V )
12
962If an inductor of inductance ( L ), radius ( r )
current changes from ( I_{1} ) to ( I_{2} ). Find work
done.
12
963A solenoid ( 30 c m ) long is made by
winding 2000 loops of wire on an iron
rod whose cross-section is ( 1.5 mathrm{cm}^{2} ). If
the relative permeability of the iron is
6000. What is the self-inductance of the
solenoid?
( mathbf{A} cdot 15 H )
в. 25H
( c .35 H )
D. ( 5 H )
12
964Current in a coil is increased at a
constant rate. The current in the second
coil is also increased at the same rate.
At a certain instant of time, the power given to the two coils is the same. At that time the current, the induced
voltage and the energy stored in the
first coil are ( I_{1}, V_{1}, ) and ( W_{1} ) respectively. Corresponding values for
the second coil at the same instant are
( I_{2}, V_{2} ) and ( W_{2} ) respectively. Then
A. ( frac{W_{2}}{W_{1}}=8 )
в. ( frac{W_{2}}{W_{1}}=frac{1}{8} )
c. ( frac{W_{2}}{W_{1}}=4 )
D. ( frac{W_{2}}{W_{1}}=frac{1}{4} )
12
965A circular ring is fixed in a gravity free
space and one point of the ring is earthed. Now a magnet is placed along
axis of the ring at a distance from its
centre such that the nearer pole is north pole as shown in figure. A sharp impilse is applied on the magnet so that it
starts to move towards the ring. Then,
A. Initially magnet experiences an acceleration and then it retards to come to an instantaneous rest.
B. Magnet starts to oscillate about centre of the ring
C. Magnet continues to move along the axis with constant velocity
D. The magnet retards and comes to rest finally
12
966A conducting disc of radius ( r ) spins about its axis with an angular velocity
( omega . ) There is a uniform magnetic field of
magnetude B perpendicular to the plane of the disc. ( C ) is the centre of the
ring. This question has multiple correct options
A. No emf is induced in the disc.
B. The potential difference between C and the rim is ( frac{1}{3} B r^{2} omega )
c. ( c ) is at a higher potential than the rim
D. Current flows between c and the rim
12
967Draw a labelled diagram of an electric
generator
12
Inglictic ilciu I mu
paper.Wire ( C D ) is in the shape of an arc
and is fixed. ( O A ) and ( O B ) are the wires
rotating with angular velocity ( omega ) as
shown in the figure in the same plane
as that of the arc about point ( O . ) If at
some instant, ( O A=O B=1 ) and each
wire makes angle ( theta=30^{circ} ) with ( y ) -axis,
then the current through resistance ( boldsymbol{R} )
is (wire ( O A ) and ( O B ) have no
resistance)
A . 0
B. ( frac{B omega l^{2}}{R} )
c. ( frac{B omega l^{2}}{2 R} )
D. ( frac{B omega l^{2}}{4 R} )
12
969If a Bismuth rod is introduced in the air
coil as shown then current in the coil
A. increases
B. remains unchanged
c. decrreases
D. none of these
12
970There are two long co-axial solenoids of
same length ( l ). the inner and outer coils
have radii ( r_{1} ) and ( r_{2} ) and number of
turns per unit length ( n_{1} ) and ( n_{2} )
respectively. The rate of mutual
inductance to the self-inductance of the
inner-coil is :
( mathbf{A} cdot frac{n_{2}}{n_{1}} cdot frac{r_{2}^{2}}{r_{1}^{2}} )
B. ( frac{n_{2}}{n_{1}} cdot frac{r_{1}}{r_{2}} )
c. ( frac{n_{1}}{n_{2}} )
D. ( frac{n_{2}}{n_{1}} )
12
971Mutual inductance of two coils can be
increased by
A. decreasing the number of turns in the coils
B. increasing the number of turns in the coils
c. winding the coils on wooden cores
D. none of these.
12
972Output emf in a dynamo is generated on
A. Magnettet
B. Armature coil
c. slip rings
D. Carbon brushes
12
97341. A magnetic flux of 5 104 Wb is associated with every 10
turns of a 500 turns coil. The electric current flowing through
the wire is 5 A. What is the self-inductance of the coil?
(a) 0.5 H
(b) 5 x 10-²H
(c) 5.0 H
(d) 5 x 10-2H
12
974A small conduction loop is in a magnetic field pointing out of the screen.Which of the following would produce a counter-clockwise current in the loop?
I. Moving the coil out of the field.
II. Increasing the strength of the field.
III. Rotating the coil on its center axis.
A. I only
B. I and III only
c. Il only
D. I, II, and III
12
975Which of the following defines electromagnetic induction:
A. When magnetic field associated with a coil changes, an induced electric current flows through the coil
B. Electric current induces magnetic field near the wire carrying current.
C. Two permanent magnets exert force on each other
D. Electrolyte disintegrates into ions in a battery.
12
976Two circular coils can be arranged in
any of the three situations shown in the
figure. Their mutual inductance will be
A. maximum in situation ( (a) )
B. maximum in situation ( (b) )
C. maximum in situation ( (c) )
D. the same in all situations
12
977In the field of electromagnetism, the term ‘EMI’ stands for:
A. Electromotive Impact
B. Electromagnetic Induction
c. Electromotive inertia
D. none of these
12
978The current in a coil of inductance ( 2 mathrm{H} ) is
changing according to varying current ( boldsymbol{I}=sin (2 t) . ) The amount of magnetic
energy in the inductor during ( t=0 ) to ( boldsymbol{t}=frac{boldsymbol{pi}}{boldsymbol{4}} boldsymbol{s} ) is:
A . 4
B . 3J
c. 1 J
D. 2
12
979A circular loop of radius ( 0.3 mathrm{cm} ) lies
parallel to a much bigger circular loop of radius ( 20 mathrm{cm} . ) The centre of the small
loop is on the axis of the bigger loop. The distance between their centres is ( 15 mathrm{cm} )
If a current of ( 2.0 A ) flows through the smaller loop, then flux liked with bigger loop is:
A ( cdot 6 times 10^{-11} ) weber
В. ( 3.3 times 10^{-11} ) weber
c. ( 6.6 times 10^{-9} ) weber
D. ( 9.1 times 10^{-11} ) weber
12
980A square loop is placed near a long straight current carrying wire as shown Match the following two columns12
981(a) Draw a labelled diagram of an
electric generator. Explain its construction and working in brief.
(b) Write down any two characteristics of magnetic field lines of a bar magnet.
12
982with an angular frequency ( omega ) with one
end hinged at the centre and the other
end at the circumference of a circular
passing through the centre and
perpendicular to the plane of the
ring.There is a magnetic field B, perpendicular to the plane of the ring. The emf induced between the centre
and the metallic ring is
A. ( B ) sinwt
( ^{mathbf{B}} cdot frac{B R^{2} omega}{2} )
( mathbf{c} cdot 2 B R^{2} omega )
D. ( B R^{2} omega )
12
983The dimensions of self-inductance L are
( mathbf{A} cdotleft[M L^{2} T^{-2} A^{-2}right] )
B. ( left[M L^{2} T^{-1} A^{-2}right] )
( mathbf{c} cdotleft[M L^{2} T^{-1} A^{-1}right] )
D. ( left[M L^{-2} T^{-2} A^{-2}right] )
12
984Identify the wrong statement
A. Eddy currents are produced in a steady magnetic field
B. Eddy currents can be minimized by using laminated core
C. Induction furnace uses eddy current to produce heat
D. Eddy current can be used to produce breaking force in moving vehicles
E. Power meters are working on the principle of eddy currents
12
985A wheel with 10 metallic spokes each ( 0.5 mathrm{m} ) long rotated with a speed of 120 rpm in a plane normal to the horizontal
component of earth’s magnetic field ( B_{h} )
at a place. If ( B_{h}=0.4 mathrm{G} ) at the place. What is the induced emf between the
axle and the rim of the wheel? ( left(1 mathrm{G}=10^{4}right. )
( T )
A. o v
B. 0.628 mV
c. ( 0.628 mu v )
D. 62.8 ( mu ) V
12
986the number of turn of primary and secondary coil of the transformer is 5 and 10 respectively ad the mutual inductance is 25 H. if the number ( f )
turns of the primary and secondary is made 10 and ( 5, ) then the mutual
inductance of the coils will be
A . ( 6.25 mathrm{H} )
B. 12.5
c. 25
D. 50
12
987An average emf of ( 32 V ) is induced in a
coil in which the current drops from
( 10 A ) to ( 2 A ) in ( 0.1 s . ) The inductance of the
coil is:
A ( .0 .32 H )
в. ( 0.4 H )
( c .4 H )
D. ( 0.04 H )
12
988An airplane with wingspan ( 50 m ) is flying horizontally with a speed of
( 360 k m h r^{-1} ) over a place where the
vertical component of the earth’s magnetic field is ( 2 times 10^{-2} ). The
potential difference between the tips of the wings would be
A. ( 100 V )
в. ( 1.0 V )
( c .0 .2 V )
D. ( 0.01 V )
12
989Describe the construction of direct
current dynamo drawing labelled diagram. Explain its working. What is the difference between direct current
and alternating current? Explain it.
12
990A rod ( A B ) moves with a uniform velocity
( boldsymbol{v} ) in a uniform magnetic field as shown in figure :
[
begin{array}{llllll}
x & x & x & x & x & x \
x & x & x & A & x & x \
x & x & x & x & x & x \
x & x & x & B x & x & x
end{array}
]
A. The rod becomes electrically charged
B. The end A becomes positively chargedd
C. The end B becomes positively charged
D. The rod becomes hot because of Joule heating
12
991Dynamo is
A. a device
B. a typr of magnet
C . a current carrying wire
D. none of these
12
99240. Two single-turn circular loops of wire have radii R and r, with
R>>r. The loops lie in the same plane and are concentric.
The mutual inductance of the pair is (approximately)
Mor?
2 Mar
(b)
R
3 Mar?
HOT2
2R
(d)
2R
10-4
W
i nted with ou
12
993Two concentric circular coils one of
small radius ( r_{1} ) and the other of large
radius ( r_{2} ) such that ( r_{1}<<r_{2} ) are placed
co-axially with centres coinciding. Obtain the mutual inductance of the
arrangement.
12
994Suggest one way to strengthen the magnetic field in the electromagnet.12
995Two large vertical and parallel metal
plates having a separation of ( 1 mathrm{cm} ) are
connected to a DC voltage source of potential difference ( X . ) A proton is
released at rest midway between the two plates. It is found to move at 45 to
the vertical JUST after release. Then X is
nearly
( mathbf{A} cdot 1 times 10^{-5} V )
B . ( 1 times 10^{-7} V )
C . ( 1 times 10^{-9} V )
D. ( 1 times 10^{-10} V )
12
996Figure shows a long straight wire
carrying current ( l ) and a square
conducting wire loop of side ( I ), at a
distance ‘a’ from current wire. Both the
current wire and loop are in the plane of
paper.Find the flux of magnetic field of
current wire,passing through the loop.
12
997The armature of a dc motor has ( 20 Omega )
resistance. It draws a current of ( 1.5 mathrm{A} )
when run by a ( 220 mathrm{V} ) dc supply. The value of the back emf induced in it is
( A cdot 150 V )
B. 170 V
c. ( 180 v )
D. ( 190 mathrm{v} )
12
998The time constant of an inductance coil
is ( 2 times 10^{-3} ) s. When a ( 90 Omega ) resistance is
joined in series, the same constant becomes ( 0.5 times 10^{-3} ) s. The inductance
and resistance of the coil are
A. ( 30 m H ; 30 Omega )
в. ( 60 m H ; 30 Omega )
c. ( 30 m H ; 60 Omega )
D. ( 60 m H ; 60 Omega )
12
999The magnetic field in the cylindrical region shown in figure increases at a
constant rate of ( 10.0 m T s^{-1} ). Each side
of the square loop abcd and defa has a
length of ( 20.0 mathrm{cm} ) and a resistance of
( 2.00 Omega . ) Correctly match the current in
the wire ( a d ) in four different situations
as listed in column I with the values
given in column II.
12
1000Define coefficient of mutual induction.
If in the primary coil of a transformer, the current decreases from ( 0.8 A ) to
( 0.2 A ) in 4 milliseconds, calculate the
induced e.m.f in the secondary coil. Mutual inductance is ( 1.76 H )
12
1001A bar magnet is dropped along the axis of copper ring held horizontally. The acceleration of fall is
A. equal to g at the place.
B. less than ( g )
c. more than ( g )
D. depends upon diameter of the ring and length of the magnet
12
1002The magnetic flux linked with a coil
satisfies the relation ( phi=4 t^{2}+6 t+9 )
Wh, where t is the time in second. The emf induced in the coil at ( t=2 s ) is
A 22 V V ( V ) ) 22
в. ( 18 V )
( mathrm{c} .16 mathrm{V} )
D. ( 40 V )
12
1003An electron accelerated by ( 200 mathrm{V} ) enters a magnetic field .If its velocity is ( 100 mathrm{m} / mathrm{sec} ). then ( (mathrm{e} / mathrm{m}) ) for it will be:
( (mathrm{C} / mathrm{Kg}) )
A. ( 1.75 times 10^{10} )
B. ( 1.75 times 10^{11} )
c. ( 1.75 times 10^{9} )
D. ( 1.75 times 10^{6} )
12
1004A conducting rod PQ of length ( L=1.0 mathrm{m} ) is
moving with a uniform speed ( v=2.0 mathrm{m} / mathrm{s} )
in a uniform field ( B=4.0 ) T directed into
the paper. A capacitor of capacity ( mathrm{C}=10 mu )
Fis connected as shown in the figure.
Then charge on the capacitor is ( 10 alpha mu mathrm{C} )
Find the value of ( boldsymbol{alpha} )
( A cdot 7 )
B. 8
( c cdot s )
D. 10
12
1005If a bar magnet is dropped vertically into a, long copper tube then its final acceleration will be
( A cdot a=g )
B. a>g
( c cdot a )
December 26, 2019
(B) ( square )
Share Save
12
1006Define:-
Electromagnetic induction.
12
1007Two coils ( P ) and ( Q ) are lying parallels and very close to each other. Coil P is
connected to an AC source whereas Q is
connected to a sensitive galvanometer. On pressing key ( mathrm{K} )
A. small variations are observed in the galvanometer for applied 50 Hz voltage
B. deflections in the galvanometer can be observed for applied voltage of 1 Hz to 2 Hz.
c. no deflection in the galvanometer will be observed
D. constant deflection will be observed in the galvanometer for 50 Hz supply voltage
12
1008( A B ) and ( C D ) are two parallel conductors
kept ( 1 mathrm{m} ) apart and connected by a resistance ( R ) of ( 6 Omega ) as shown in figure.
They are placed in a magnetic field ( B= )
( 3 times 10^{-2} mathrm{T} ) which is perpendicular to the
plane of the conductors and directed
into the paper. A wire MN is placed over
( A B ) and ( C D ) and then made to slide with
velocity ( 2 m s^{-1} . ) (Neglect the resistance of ( A B, C D, ) and ( M N ) ). Calculate the induced current flowing through the resistor R.
12
1009AC generator means
A. Acquired continuity generator
B. Assistant current generator
C . Alternating current generator
D. none
12
1010A satellite orbiting the Earth at ( 400 mathrm{km} ) above the surface of the Earth has a ( 2 m )
long antenna oriented perpendicular to
the Earth’s surface. At the equator the Earth’s magnetic field is ( 8 times 10^{-5} T ) and
is horizontal. Assuming the orbit to the circular, find emf induced across the
ends of the antenna.(Given radius of
( left.operatorname{earth} R_{e}=6400 K mright) )
A. ( 1.3 V )
В. ( 1.2 V )
c. ( 1.0 V )
D. ( 0.12 V )
12
1011When a straight wire is moved up and down rapidly between two poles of a horseshoe magnet then is
produced in the wire.
A. magnetic field
B. magnetic current
c. electric current
D. none
12
1012The self induction takes place when
magnetic flux through a coil:
B. Decreases
c. Increases
D. Either (B) or (C)
12
1013The relation between ( left[in_{0}right] ) and ( left[mu_{0}right] ) is
A ( cdotleft[mu_{0}right]=left[epsilon_{0}right][L]^{2}[T]^{-2} )
B . ( left[mu_{0}right]=left[epsilon_{0}right][L]^{-2}[T]^{2} )
C ( cdotleft[mu_{0}right]=left[epsilon_{0}right]^{-1}[L]^{2}[T]^{-2} )
D ( cdotleft[mu_{0}right]=left[epsilon_{0}right]^{-1}[L]^{-2}[T]^{2} )
12
1014Complete the sentence by using the
correct words given in the brackets:
( A_{-}-_{-}-_{-}-_{-} ) (generator ( / ) transformer/motor/transducer) is a
source of electricity that generates large amount of electricity in a power house.
A. Motor
B. Generator
c. Transducer
D. Transformer
12
1015Two coils have a mutual inductance of
( 0.005 H . ) The current changes in the first coil according to equation ( boldsymbol{I}= )
( I_{0} )sin( omega t, ) where ( I_{0}=10 A ) and ( omega= )
100 ( pi ) rad / s. The maximum value of emf
(in volt) in the second coil is.
A . ( 2 pi )
в. ( 5 pi )
c. ( pi )
D. ( 4 pi )
12
1016The instrument which works on the
principle of mutual inductance is
A. Galvanometer
B. Ammeter
c. Potentiometer
D. Transformer
12
101761. Switch S shown in figure is closed for t < 0 and is opened
at t= 0. When currents through L, and L, are equal, their
common value is
2
LR 8
L2
E(L₂+4)
S
RL
EL
R(L + L₂)
E (4 + L2)
R L2
12
1018If the self inductance of 500 turns coil
is ( 125 mathrm{mH} ), then the self inductance of
the similar coil of ( 800 mathrm{mH} )
A. ( 48.8 mathrm{mH} )
B. 200 mH
c. ( 290 mathrm{mH} )
D. 320 mH
12
1019Figure shows a fixed square frame of
wire having a total resistance r placed
coplartarly with a long, straight wire
The wire carries a current i given by ( i= )
( i_{2} cos (2 pi t / T), ) Find ( (a) ) the flux of the
magnetic field through the square frame
(b) the emf induced in
the frame and
(c) the heat developed in the frame in the time interval 0 to 10 T.
12
1020What will be the magnitude of e.m.f.
induced in a 200 turns coil with cross
section area ( 0.16 m^{2} ? ) The magnetic
field through the coil changes from ( 0.10 W b m^{-2} ) to ( 0.30 W b m^{-2}, ) at a
uniform rate over a period of 0.05 s
( mathbf{A} cdot 128 V )
B. ( 130 V )
c. ( 118 V )
D. ( 132 V )
12
1021A conductor ABOCD moves along its
bisector with a velocity of ( 1 mathrm{ms}^{-1} ) through a perpendicular magnetic field
of ( 1 mathrm{Wbm}^{-2} ), as shown in the figure. If all
the four sides are of ( 1 mathrm{m} ) length each,
then the induced emf between point ( A )
and D is :
A. zero
в. 1.41
( c cdot 0.71 v )
D. none of the above
12
1022An aluminum ring B faces an electromagnet A. The current
I through A can be altered
Front
side
Observer
Rear
side
(a) whether I increases or decreases, B will not experience
any force
(b) if I decrease, A will repel B
(c) if I increases, A will attract B
(d) if I increases, A will repel B
11
od
12
1023Select the incorrect option
A. Luminous flux and radiant flux have same dimensions
B. Luminous flux and luminous intensity have same dimensions
C. Radiant flux and power have same dimension
D. Relative luminosity is a dimensionless quantity
12
1024(a) A rod of length I is moved horizontally with a uniform velocity ‘v’ in a direction perpendicular to its length
through a region in which a uniform magnetic field is acting vertically downward. Derive the expression for the
emf induced across the ends of the rod.
(b) How does one understand this
motional emf by invoking the Lorentz force acting on the free charge carriers of the conductor? Explain.
12
1025In a circuit a coil of resistance ( 2 Omega ), then
magnetic flux charges from 2.0 ( W ) b to
10.0 ( W b ) in 0.2 sec. The charge flow in
the coil during this time is:
( mathbf{A} cdot 5.0 C )
в. ( 4.0 C )
c. ( 1.0 C )
D. ( 0.8 C )
12
1026Fill in the blanks.
The type of electric current that
changes its direction twice during one cycle of the dynamo is called
12
1027Current in a circuit falls from ( 5.0 A ) to
( 0.0 A ) in ( 0.1 s . ) If an average emf of ( 200 V )
induced, find an estimate of the selfinductance of the circuit.
12
1028R
14
76. Two identical inductance carry
currents that vary with time according
to linear laws (as shown in figure). In
which of two inductance is the self-
induction emf greater?
(a) 1
(b) 2
(c) same
(d) data are insufficient to decide
12
1029A conducting rod of length ( l ) falls
vertically under gravity in a region of uniform magnetic field ( vec{B} ). The field vectors are inclined at an angle ( boldsymbol{theta} ) with
the horizontal as shown in figure. If the
instantaneous velocity of the rod is ( boldsymbol{v} )
the induced emf in the rod ( a b ) is:
( mathbf{A} cdot B l v )
B. ( B l v cos theta )
c. ( B l v sin theta )
D. zero
12
1030The equivalent quantity of mass in electricity is :
A. current
B. self inductance
c. potential
D. charge
12
1031A field of strength ( 5 times 10^{4} / pi ) ampere
turns / meter acts at right angles to the
coil of 50 turns of area ( 10^{-2} m^{2} . ) The coil
is removed from the field in 0.1 second.
Then the induced e.m.f. in the coil is :
A . ( 0.1 V )
B. ( 0.2 V )
c. ( 1.96 V )
( mathbf{D} cdot 0.98 V )
12
1032Assertion
Two coaxial conducting rings of different radii are placed in space. The mutual inductance of both the rings is
maximum if the rings are also coplanar
Reason
For two coaxial conducting rings of different radii, the magnitude of
magnetic flux in one ring due to current in the other is maximum when both the
rings are coplanar.
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
1033What do you mean by electric generator? Differentiate between a.c. and d.c generators on the basis of
construction.
12
1034( begin{array}{ll}text { Table } 1 & text { Table } 2 \ begin{array}{l}text { (a) If current is } \ text { increased }end{array} & begin{array}{l}text { (p) Induced current in } \ text { loop is clockwise }end{array} \ begin{array}{l}text { (b) If current is } \ text { decreased }end{array} & begin{array}{l}text { (q) Induced current in } \ text { loop is anticlockwise }end{array} \ begin{array}{l}text { (c) If loop is moved } \ text { away from the wire }end{array} & begin{array}{l}text { (r) Wire will attract the } \ text { loop }end{array} \ begin{array}{l}text { (d) If loop is moved } \ text { towards the wire }end{array} & begin{array}{l}text { (s) wire will repel the } \ text { loop }end{array}end{array} )
A square loop is placed near a long straight current carrying wire as shown, match the following table
1
( A cdot a-q, s ; b-p, r ; c-q, s ; d-p, r )
B. ( a-p, r ; b-q, s ; c-p, r ; d-q, s )
c. ( a-q, s ; b-p, r ; c-q, r ; d-p, q )
D. ( a-q, s ; b-p, r ; c-p, r ; d-q, s )
12
y ( D-D_{0}lfloorbar{a} / ) kappa.
bo 14
( d ) is placed with it’s edges on the ( x ) and ( y )
axis. The loop is moved with a constant velocity ( vec{v}=v_{0} hat{i} . ) The emf induced in
the loop is :
A ( cdot B_{0} v_{0} d )
B. ( frac{B_{0} v_{0} d^{2}}{2 a} )
c. ( frac{B_{0} v_{0} d^{3}}{a^{2}} )
D. ( frac{B_{0} v_{0} d^{2}}{a} )
12
1036The figure shows a conducting ring of radius ( R ). A uniform steady magnetic
field ( B ) lies perpendicular to the plane of
the ring in a circular region of radius ( r(<R) . ) If the resistance per unit length
of the ring is ( lambda ), then the current induced
in the ring when its radius gets doubled
is
( ^{A} cdot frac{B R}{lambda} )
B. ( frac{2 B R}{lambda} )
( mathbf{c} . ) zero
D. ( frac{B r^{2}}{4 R lambda} )
12
1037A coil of area ( 5 mathrm{cm}^{2} ) with 20 turns is
kept under the magnetic field of ( 10^{3} ) Gauss. Normal to the plane of coil
makes an angle ( 30^{circ} ) with the magnetic field. The flux through the coil is
A ( cdot 6.67 times 10^{-4} mathrm{Wb} )
B. ( 3.2 times 10^{-5} mathrm{Wb} )
( mathbf{c} cdot 5.9 times 10^{-4} W b )
D. ( 8.65 times 10^{-4} W b )
12
1038The north pole of a bar magnet is moved towards a coil along the axis passing through the centre of the coil when viewed in the direction of the motion of
the magnet direction of induced current
is:
A. clockwise
B. Anti – Clockwise
c. No current in the coil
D. Either clockwise or anti-clockwise
12
parallel smooth conducting rails. A conducting rod lies on these fixed
horizontal rails and a uniform
constant magnetic field ( B ) exists
perpendicular to the plane of the rails as shown in the figure. If the rod is given
a velocity ( v ) and released as shown in
figure, it will stop after some time. The
total work done by magnetic field is negative

STATEMENT – 2 : If force acts opposite to direction of velocity its work done is negative.
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
1040Lenz’s law is a consequence of law of conservation of
A. momentum
в. energy
c. charge and mass
D. angular momentum
12
1041Two coils ( A ) and ( B ) are separated by a certain distance. If a current of ( 4 mathrm{A} )
flows through ( A, ) a magnetic flux of ( 10^{-3} )
Wh passes through B (no current through B).If no current passes through A and a current of 2 A passes through ( B ), then the flux through ( A ) is then
A ( .5 times 10^{-3} )
B . ( 4 times 10^{-4} )
c. ( 5 times 10^{-4} )
D. ( 2 times 10^{-3} )
12
1042A body enters in MRI machine in 10 sec
If the magnetic field is ( 1.5 T ) and
circumference of MRI machine is ( 0.9 m )
then find out emf induced in the body.
A . ( 0.96 V )
B. ( 9.6 V )
c. ( 9.6 m V )
D. ( 96 m V )
12
1043When a coil of cross-sectional area ( A )
and number of turns N is rotated in a
uniform magnetic field B with angular velocity ( omega, ) then the maximum emf
induced in the coil will be
A. BNA
в. ( frac{B a omega}{N} )
c. BNAomega
D. zero
12
1044A circular coil of ( n ) turns is kept in a uniform magnetic field such that the plane of the coil is perpendicular to the field. The magnetic flux associated with
the coil is now ( phi . ) Now the coil is opened
and made into another circular coil
of twice the radius of the previous coil and kept in the same field such that the plane of the coil is perpendicular to the field. The magnetic flux associated with this coil now is:
( A cdot phi )
B. 2
( c cdot frac{phi}{4} )
D. ( frac{phi}{2} )
12
1045A small coil is introduced between the
poles of an electromagnet so that its axis coincides with the magnetic field
direction. The cross-sectional area of
the coil is equal to ( S=3.0 m m^{2}, ) the
number of turns is ( N=60 . ) When the
coil turns through ( 180^{circ} ) about its diameter, a galvanometer connected to the coil indicates a charge ( boldsymbol{q}=mathbf{4 . 5} boldsymbol{mu} boldsymbol{C} )
flowing through it. Find the magnetic induction magnitude between the poles, provided the total resistance of the electric circuit equals ( R=40 Omega )
12
104673 PO is an infinite current carrying conductor. AB and CD
are smooth conducting rods on which a conductor EF
moves with constant velocity v as shown. The force needed
to maintain constant speed of EF is.
PL ano
I EF
ol
B
To
a
OJĂ w
12
1047Weber ( / m^{2} ) is equal to
A. dyne
B. tesla
c. watt
D. henry
12
1048A rod of length ( 50 mathrm{cm} ) moves with a
speed of ( 10 mathrm{cm} / mathrm{s} ), in a uniform
magnetic field of strength ( 10 G ) at an
angle of ( 30^{circ} ) with the field. The emf
induced across the ends of the rod is :
A. 5000 CGS unit
B. ( 2500 mathrm{CGS} ) unit
c. 7500 CGS unit
D. ( 1000 mathrm{CGS} ) unit
12
1049toppr OGII
( +y^{prime}=4 ) where ( x ) and ( y ) are in meters.
wire frame ( A_{1} A_{2} A_{4} A_{3} A_{1} ) is placed in
the magnetic field as shown. Segment ( mathbf{A} )
( A_{2} ) and ( A_{3} A_{4} ) are identical
quarter circles parallel to each other
with axis along z-axis.The induced
current flowing in the wire frame is
equal to : (The total length of the loop of
wire frame is ( 10 mathrm{m}, ) radius of arc ( mathrm{A}_{3} mathrm{A}_{4} )
and arc ( A_{1} A_{2} ) is ( 1 mathrm{m} ) each and resistance
per unit length is ( 1 Omega / m ) ):
( A cdot ) zero
В. ( frac{B_{0} pi}{10} )
c. ( frac{B_{0} pi}{5} )
D. ( frac{B_{0} pi}{20} )
12
1050If a magnet is dropped through a vertical hollow copper tube, then?
A. The time taken to reach the ground is longer than the time taken, if the tube was made out of plastic
B. The magnet will get attracted and stick to the copper tube
C. The time taken to reach the ground is longer than the time taken, if the tube was made out of stainless steel
D. The time taken to reach the ground does not depend on the radius of the copper tube
E. The magnet will be repelled away by the tube
12
1051A circular loop of radius ( r ) is placed at
the centre of current carrying
conducting square loop of side ( a . ) If both
loops are coplanar and ( a>>r, ) then the
mutual inductance between the loops
will be:
A ( frac{mu_{0} r^{2}}{2 sqrt{2}(a)} )
B. ( frac{mu_{0} r^{2}}{4 a} )
c. ( frac{2 sqrt{2} mu_{0} r^{2}}{pi a} )
D. ( frac{mu_{0} r^{2}}{4 sqrt{2} a} )
12
1052The magnetic flux linked with a coil
setisfies the relation ( phi=4 t^{2}+6 t+ )
( 9 W b, ) where ( t ) is the time (in ( s ) ). The
emf indused in the coilat ( t=2 s ) is, (in
( mathbf{V}) )
( mathbf{A} cdot 22 )
B . 18
c. 16
D. 40
12
1053A current of ( 3.14 A ) flows in an infinitely long wire with cross section in the form of a semicircular ring of radius ( 5 mathrm{cm} ) The magnitude of magnetic induction on its axis is :
A . ( 8.0 times 10^{-6} T )
В. ( 1.6 times 10^{-5} T )
c. ( 2.0 times 10^{-5} T )
D. ( 4.0 times 10^{-6} T )
12
1054For a coil having ( L=2 m H, ) current
flow through it is ( I=t^{2} e^{-t} ) then the
time at which emf becomes zero:
( mathbf{A} cdot 2 sec )
B. 1 sec
( mathbf{c} cdot 4 sec )
D. 3 sec
12
1055What is the unit for EMF?
A. Ampere
B. Potential
c. watt
D. volt
12
1056What is the Sl unit of self-inductance?
A. Henry
B. Tesla
c. weber
D. Gauss
12
1057If a current carrying coil is close to a magnet and both are moving with the same speed in same direction, what is
the effect on induced current?
A. Induced current increases
B. Induced current decreases
c. Induced current flows to oppose motion
D. Induced current remains equal to zero
12
1058by
6. A thin semicircular conducting ring of radius R is falling
with its plane vertical in a
horizontal magnetic induction B
B. At the position MNQ, the
speed of the ring is v and the
potential difference developed
across the ring is
(a) zero
(b) ByaR-/2 and Mis at higher
potential
(c) TRBv and Q is at higher potential
(d) 2RBv and Q is at higher potential
man of the camicircular ring
12
1059Assertion
When the electric current in a loop of wire changes, the changing current
creates a changing magnetic field.
Reason
Magnetic field lines of a circular loop of
wire is same as a magnet.
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
1060Current ( i ) is flowing in each of the two similar coaxial circular coils in the
same direction. If the loops are moved towards each other, the following
phenomenon will happen:
A. current in each loop will remain same
B. current in each loop will increase
c. current in each loop will decrease
D. current in one loop will increase and that in another loop will decrease
12
1061An alternating current can be produced
by:
A. transformer
B. generator
c. turbine
D. electric motor
12
1062(i) Define mutual inductance.
(ii) A pair of adjacent coils has a
mutual inductance of 1.5 H. If the
current in one coil changes from 0 to
( 20 A ) in ( 0.5 s, ) what is the change of flux linkage with the other coil?
12
1063According to Faraday’s law, the total charge induced in a conductor that is moved in a magnetic field depends upon
A. Initial magnetic flux
B. Final magnetic flux
c. Rate of change of magnetic flux
D. change in magnetic flux
12
1064In a circuit the coil of a choke:
A. Decreases the current
B. Increases the current
C. Has high resistance to D. C. circuit
D. No effect with the current
12
1065Figure shows a conducting loop placed near a long straight wire carrying a current ( i ) as shown. If the current
increases continuously, then the direction of the induced current in the
loop is clockwise.
True or false?
12
1066The emf induced in the circuit is
A. ( 125 mu V )
B. ( 250 mu V )
c. ( 100 mu V )
( mathbf{D} cdot 300 mu V )
12
1067Current 1 in a long ( 4 y- ) axis is paced through a square metal frame of side
( 2 a ) oriented in the ( y-z ) p[lane a shown.
The linear mass density of the frame is
( lambda . ) A uniform magnetic field ( B ) is now
switched on along ( x- ) axis. Then the
instantaneous angular acceleration of
the frame will be:
A ( cdot frac{4 I B}{lambda_{n}} )
В. ( frac{12 I B}{lambda a} )
c. ( frac{4 I B}{3 lambda a} )
( D )
12
1068A coil of wire of a certain radius has 100
turn and a self-inductance of 15 mH. The
self-inductance of a second similar coil
of 500 turns will be :
( mathbf{A} cdot 75 m H )
в. 375 тН
c. ( 15 m H )
D. none of these
12
1069A copper ring is moved towards the
north pole of a bar magnet. Then
A. the ring will not be affected
B. the ring all tend to get warm
c. an alternating current will flow in the ring
D. the ring will be positively charged
12
1070On what principle ( A C ) generator works?12
1071Draw a labelled diagram of an alternating current Generator. Determine the induced electromotive
force by the rotation of coil in it.
12
1072If ( N ) is the number of turns in a circular
coil then the value of self inductance
varies as
A . ( N^{0} )
в. ( N )
( c cdot N^{2} )
D. ( N^{-2} )
12
1073Derive the expression for motional EMF induced in a conductor moving in a uniform magnetic field.12
1074What is the effect on self inductance of
a solenoid, if a core of soft iron is placed in it?
12
1075In the figure magnetic field points into the plane of paper and the conducting
rod of length ( l ) is moving in this field
such that the lowest point has a velocity
( boldsymbol{v}_{1} ) and the topmost point has the
velocity ( v_{2}left(v_{2}>v_{1}right) . ) The emf induced is
given by:
[
begin{array}{cccc}
x & x & x & x \
x & x & x_{2} & x \
x & x & x & x \
x & vec{x} & v_{1} & x & x
end{array}
]
( mathbf{A} cdot B v_{1} l )
B. ( B v_{2} l )
( c )
[
frac{1}{2} Bleft(v_{2}+v_{1}right) l
]
D.
[
frac{1}{2} Bleft(v_{2}-v_{1}right) l
]
12
1076Lenz’s law is in accordance with the law
of conservation of
A. electric current
B. energy
c. electro motive force
D. electric charge
12
1077The voltage induced across a certain
coil is ( 200 m V . A 120 Omega ) resistor is
connected to the coil terminals. The
induced current is
A ( .1 .7 m A )
в. ( 16 m A )
c. ( 12 m A )
D. ( 120 m A )
12
1078A long coaxial cable consists of two thin-walled conducting cylinders with
inner radius ( 2 c m ) and outer radius ( 8 c m )
The inner cylinder carries a steady current ( 0.1 A ), and the outer cylinder
provides the return path for that current. The current produces a magnetic field between the two cylinders. Find the energy stored in the
magnetic field for length ( 5 m ) of the
cable. Express answer in ( n J ) (use
( ln 2=0.7) )
12
1079A cnarge + ( ell ) Is locatea somewnere
inside a vertical cone such that the
dept of the charge from the free surface
of the cone is ( H . ) It is formed that the
flux associated with the cone with thw
curved surface is ( frac{3 Q}{5 epsilon_{0}} )

If the charge is raised vertically through a height ( 2 H ) then the flux through the curved surface is
( mathbf{A} cdot frac{3 Q}{5 epsilon_{n}} )
B. ( frac{2 Q}{5 epsilon_{n}} )
( c cdot frac{4 Q}{5 epsilon_{n}} )
D. Zero

12
1080and conducting
(c) 1.001
71. A simple pendulum with bob of mass m and condu
wire of length L swings under gravity through an anal
20. The earth’s magnetic field component in the directi
perpendicular to swing is B. Maximum potential differen
induced across the pendulum is
(a) 2BL sin)(82)2 (6) BL sin (8L)
(C) BLsin)(8L)2 (a) BLsin) (8L)?
12
1081Fill in the blanks.
In Flemings rule the middle finger
indicates the direction
of
12
1082Who gave the principle of Electromagnetic induction?
A. Volta
c. Ampere
12
1083A conducting straight wire ( P Q ) of length
is fixed along a diameter of a nonconducting ring as shown in the figure. The ring is given a pure rolling motion
on a horizontal surface such that its
centre of mass has a veleocity ( v ). There
exists a uniform horizontal magnetic field ( B ) in horizontal direction
perpendicular to the plane of ring. The magnitude of induced emf in the wire
( P Q ) at the position shown in the figure
will be :
A. ( B v )
в. 2 Ву
c. ( 3 B v l / 2 )
D. zer
12
1084A coil of insulated copper wire is connected to a galvanometer. What would happen if a bar magnet is (i) Pushed into the coil?
A. The galvanometer shows deflection
B. The galvanometer do not show any deflection
c. Current increases inside the coil
D. none
12
1085The coefficient of mutual induction
between two coils is ( 4 mathrm{H} ). If the current in
the primary reduces from 5 A to zero in ( 10^{-3} ) second then the induced emf in the
secondary coil will be
A ( cdot 10^{4} v )
B . ( 25 times 10^{3} mathrm{V} )
C ( cdot 2 times 10^{4} mathrm{V} )
( mathbf{D} cdot 15 times 10^{3} mathbf{v} )
12
1086Assertion: Magnetic flux is a vector quantity Reason: Value of magnetic flux can be positive, negative or zero
A. Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
c. Assertion is true but Reason is false
D. Assertion is false but Reason is true
12
1087A conducting loop rotates with constant
diameter in a uniform magnetic field,
whose direction is perpendicular to that
fixed diameter
This question has multiple correct options
A. The emf will be maximum at the moment when flux is
zero
B. The emf will be 0 at the moment when flux is maximum
C. The emf will be maximum at the moment when plane of the loop is parallel to the magnetic field
D. The phase difference between the flux and the emf is ( pi / 2 )
12
1088Distinguish between electric motor and electric generator12
1089A closed coil consists of 500 turns on a
rectangular frame of area ( 4.0 mathrm{cm}^{2} ) and has a resistance of 50 ohms. The coil is
kept with its plane perpendicular to a uniform magnetic field of ( 0.2 mathrm{wb} / mathrm{m}^{2} ) the amount of charge flowing through the coil if it is turned over. (rotated
through ( 180^{0} ) ):
A ( cdot 1.6 times 10^{-3} mathrm{c} )
B. ( 16 times 10^{-3} mathrm{C} )
c. ( 0.16 times 10^{-3} mathrm{c} )
D. ( 160 times 10^{-3} mathrm{c} )
12
1090Through an inductance coil of ( boldsymbol{L}= )
( 0.2 H, ) an ac current of 2 ampere is
passed first with frequency ( n_{1} ) and then
with frequency ( n_{2} ). The ratio of the
maximum value of induced emf ( left(e_{1} / e_{2}right) )
in the coil, in the two cases is
A. ( n_{1} / n_{2} )
в. ( n_{2} / n_{1} )
c. ( n_{1}^{2} / n_{2}^{2} )
D ( cdot n_{2}^{2} / n_{1}^{2} )
12
1091Assertion
An emf ( vec{E} ) is induced in a closed loop
where magnetic flux is varied. The induced ( vec{E} ) is not a conservative field.
Reason The line integral ( overrightarrow{boldsymbol{E}} cdot boldsymbol{d l} ) around
the closed loop is nonzero.
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
1092The rate of change of current needed to induce an emf of ( 8 V ) in ( 0.1 H ) coil is
A . ( 0.8 A / s )
В. ( 0.125 A / s )
c. ( 80 A / s )
D. ( 8 A / s )
12
1093A loop made of straight edges has six corners at ( A(0,0,0), B(L, 0,0), c(L, L, 0) )
( mathrm{D}(0, mathrm{L}, 0), mathrm{E}(0, mathrm{L}, mathrm{L}) ) And ( F(0,0, mathrm{L}) )
A magnetic field ( bar{B}=B_{0}(hat{i}+hat{k}) T ) is
present in the region.The flux passing through the loop ABCDEFA (in the order)
is
A. ( B_{0} L^{2} W b )
В ( cdot 2 B_{0} L^{2} W b )
c. ( sqrt{2} B_{0} L^{2} W b )
D. ( 4 B_{0} L^{2} W b )
12
1094The magnetic induction at the centre 0
is?
12
10958. A thin circular ring of area A is perpendicular to uniform
magnetic field of induction B. A small cut is made in the
ring and a galvanometer is connected across the ends such
that the total resistance of circuit is R. When the ring is
suddenly squeezed to zero area, the charge flowing through
the galvanometer is
(a) BR
(b) AB
A
(c) ABR
R
(d) B-A/R2
12
1096A ( 1.2 mathrm{m} ) wide railway track is parallel to magnetic meridian. The vertical component of earth’s magnetic field is 0.5 Gauss. When a train runs on the
rails at a speed of ( 60 mathrm{Km} / mathrm{hr} ), then the
induced potential difference the ends of its axle will be
( A cdot 10^{-4} v )
B . ( 2 times 10^{-4} mathrm{V} )
c. ( 10^{-3} mathrm{v} )
D. zero
12
1097Henry, the Sl unit of inductance can be
written as :
A. weber ampere-
B. volt second ampere ( ^{-1} )
c. joule ampere ( ^{-1} )
D. ohm s ( ^{-1} )
12
1098Two sources of equal emf are connected to an external resistance R. The internal
resistances of two sources are ( boldsymbol{R}_{1} ) and
( boldsymbol{R}_{2}left(boldsymbol{R}_{2}>boldsymbol{R}_{1}right) . ) If the potential difference
across the source having internal
resistance ( R_{2} ) is zero, then;
в. ( R=R_{1} R_{2} /left(R-R_{1}right) )
C. ( R=R_{2} timesleft(R_{1}+R_{2}right) /left(R_{2}-R_{1}right) )
D. ( R=R_{2}-R_{1} )
12
1099A square loop of side a lying a perpendicular magnetic field to its plane is changed to a circle. If change occusrs in ( t ) seconds in magnetic field ( B ) tesla, the induced emf is
A ( cdot frac{4}{pi} frac{B a^{2}}{t} )
B. ( frac{B a^{2}}{t} )
c. ( frac{B a^{2}}{t}left[frac{4}{pi}-1right] )
D. zero
12
1100* Explain the construction and working of an electric generator (AC). Draw a neat diagram and label it.12
1101An electric generator actually acts as:
A. source of electric charge
B. source of heat energy
c. an electromagnet
D. a converter of energy
12
110221. A coil is suspended in a uniform magnetic field, with
the plane of the coil parallel to the magnetic lines of
force. When a current is passed through the coil it starts
oscillating; it is very difficult to stop. But if an aluminium
plate is placed near to the coil, it stops. This is due to
(a) developement of air current when the plate is placed
(b) induction of electrical charge on the plate
(c) shielding of magnetic lines of force as aluminium is
a paramagnetic material
(d) electromagnetic induction in the aluminium plate
giving rise to electromagnetic damping
(AIEEE 2012
12
110310
TUU
29. Two identical cycle wheels (geometrically) have differen
number of spokes connected from center to rim. One is
having 20 spokes and the other having only 10 (the rim and
the spokes are resistanceless). One resistance of value Ris
connected between center and rim. The current in R will be
(a) double in the first wheel than in the second wheel
(b) four times in the first wheel than in the second wheel
(c) will be double in the second wheel than that of the
first wheel
(d) will be equal in both these wheels
1
fredinu
D follo
12
1104A coil of area ( 80 mathrm{cm}^{2} ) and number of
turns 50 is rotating about an axis perpendicular to a magnetic field of 0.05 Tesla at 2000 rotations per minute The maximum value of emf induced in
¡it will be
A . ( 200 pi ) volt
в. ( frac{10 pi}{3} ) volt
c. ( frac{4 pi}{3} ) volt
D. ( frac{2}{3} ) volt
12
1105A flux of ( 1 m W b ) passes through a strip
having an area ( A=0.02 m^{2} . ) The plane
of the strip is at an angle of ( 60^{circ} ) to the
direction of a uniform field B. The value
of B is:
A . ( 0.1 T )
B. ( 0.058 T )
c. ( 4.0 m T )
D. None of the above
12
1106The maximum emf induced in the coil
will be
( A )
( ^{text {В } cdot} frac{pi^{2} N B_{0}left(a^{2}+a b+b^{2}right)}{T} )
( c )
( D )
12
1107A flat coil, ( C ) of ( n ) turn, area ( A ) and
resistance ( R ), is placed in a uniform
magnetic field of magnitude ( boldsymbol{B} ). The plane of the coil is initially perpendicular to ( B ). The coil is rotated
by an angle ( theta ) about a diameter and
charge of amount ( Q ) flows through it. The plane of the coil is initially kept
parallel to ( B ). The coil is rotated by an
angle ( theta ) about the diameter
perpendicular to ( B ) and charge of
amount ( Q ) flows through it.Choose the correct alternatives
This question has multiple correct options
A ( cdot theta=90^{circ}, Q=(operatorname{Ban} / R) )
B . ( theta=180^{circ}, Q=(2 B a n / R) )
C ( cdot theta=180^{circ}, Q=0 )
D . ( theta=360^{circ}, Q=0 )
12
1108A uniform field of induction ( B ) is
changing in magnitude at a constant rate ( d B / d t . ) You are given a mass ( m ) of copper which is to be drawn into a wire
of radius ( r ) and formed into a circular
loop of radius ( R ). Show that the induced current in the loop does not depend on the size of the wire of the loop.

Assuming ( B ) perpendicular the loop
prove that the induced current ( i= ) ( frac{m}{4 pi rho delta} frac{d B}{d t} ) where ( rho, ) is the resistivity and
( d ) is the density of copper

12
1109The change in magnetic field lines in a coil is the cause of induced electric
current in it. Name the underlying phenomenon.
12
1110The conducting rod ( a b ), as shown in figure makes contact with metal rails
( c a ) and ( d b . ) The apparatus is in a uniform magnetic field of ( 0.800 T ), perpendicular to the plane of the figure. If the
resistance of the circuit ( a b d c ) is ( 1.50 Omega )
(assumed to be constant), find the force (magnitude and direction) required to keep the rod moving to the right with a constant speed of ( 7.50 m / s . ) You can
ignore friction.
12
1111Lenz’s law is based on conservation of
A. charge
B. mass
c. energy
D. momentum
12
1112A closed coil having 100 turns is rotated
in a uniform magnetic field ( B=4.0 times )
( 10^{-4} T ) about a diameter which is
perpendicular to the field. The angular velocity of rotation is 300 revolution per minute. The area of the coil is ( 25 mathrm{cm}^{2} )
and its resistance is ( 4.0 Omega . ) Find (a) the average emf developed in half a turn from a position where the coil is perpendicular to the magnetic field,
(b)the average emf in full turn and the net charge displaced in part (a).
12
1113Assertion(A): The possibility of an electric bulb fusing is higher at the time of switching on and off
Reason(R): Inductive effects produce a large current at the time of switch-on
and switch-off.
A. Both A and R are individually true and R is the correct explanation of A
B. Both A and R are individually true but R is not the correct explanation of ( A )
c. A is true but R is false
D. Both A and R are false
12
1114DD OUT)
16 Two coaxial solenoids are made by winding a thin
insulated wire over a pipe of cross-sectional area
A = 10 cm’ and length 20 cm. If one of the solenoids
has 300 turns and the other 400 turns, their mutual
inductance is (Mo = 4 ntx 10-T m/A)
(a) 4.78 1 x 10-H (b) 2.4 t x 104 H
(c) 2.4 A x 10-H (d) 4.8 x 104 H
(AIEEE 2007)
12
1115Derive Faradays law of induction from law of conservation of energy.12
1116A copper disc of radius 0.1 m rotated
about its centre with 10 revolutions per
second in a uniform magnetic field of
0.1 tesla with it’s plane perpendicular to the field. The e.m.f. induced across the
A ( cdot frac{pi}{10} ) volt
в. ( frac{2 pi}{10} ) volt
c. ( pi times 10^{-2} ) volt
D. 2 ( pi times 10^{-2} ) volt
12
1117( frac{sqrt{3}}{frac{1}{4}} )12
1118The armature of a generator of resistance ( 1 Omega ) is rotated at its rated
speed and produces ( 125 V ) without load
and ( 115 V ) with full load. The current in
the armature coil is
( mathbf{A} cdot 240 A )
в. ( 10 A )
( c .1 A )
D. ( 2 A )
12
1119For the situation described in figure
the magnetic field changes with time
( operatorname{according} ) to ( boldsymbol{B}=left(mathbf{2} . mathbf{0 0} boldsymbol{t}^{3}-mathbf{4 . 0 0} boldsymbol{t}^{2}+right. )
0.8)( T ) and ( r_{2}=2 R=5.0 mathrm{cm} )
a) Calculate the force on an electron
located ( a t P_{2} ) at ( t=2.00 s )
b) What are the magnitude and
direction of the electric field at ( P_{1} ) when
( t=3.00 mathrm{s} ) and ( r_{1}=0.02 m )
12
1120Derive the expression for the self
inductance of a long solenoid of cross
sectional area ( A ) and length ( l ), having ( n )
turns per unit length.
12
1121ROV
WWW
17. A rectangular loop has
a sliding connector
PQ of length 1 and
resistance R ohm and
it is moving with a
speed vas shown.
The set up is placed
in a uniform magnetic
field going into the plane of the paper.
The three currents 11, 12, and I are
(a) I, = – 12 = PI = 2B
(b) 11 = 1 = Bk 1 = 2 BRD
(©) I, = 12 = 1 = Bly
(d) 1, = 12 = BR 1 = BR
(AIEEE 2010)
12
1122The magnetic needle of a tangent galvanometer is deflected at an angle 30 due to a magnet. The horizontal component of earth’s magnetic field
( 0.34 times 10^{-4} T ) is along the plane of the
coil. The magnetic intensity is:
A . ( 1.96 times 10^{-4} T )
B . ( 1.96 times 10^{-5} T )
c. ( 1.96 times 10^{4} T )
D. ( 1.96 times 10^{5} T )
12
1123A coil of self-inductance ( L ) is connected
in series with a bulb B and an AC
source. Brightness of the bulb decreases when :
A. frequency of the AC source is decreased
B. number of turns in the coil is reduced
C . a capacitance of reactance ( X_{C}=X_{L} ) is included in the same circuit
D. an iron rod is inserted in the coil
12
1124In faraday’s experiment current in not
produced in
A. the coil is moved and magnetic is stationary
B. the magnetic is moved the coil is stationary
C. both coil and magnetic are moved in same direction with same speed
D. both coil and magnet stationary
12
1125what emf ( E ) of the source must be
applied to maintain the required current? Consider the total resistance
of the circuit to be constant and equal
to
( R . ) Disregard the inductance of the circuit.
12
1126The magnetic flux linked with a coil at
any instant ( t ) is given by the equation
( phi=5 t^{3}-100 t+300 . ) The magnitude
of emf induced in the coil after ( 3 s ) is
A . ( 10 V )
в. ( 20 V )
( c .35 V )
D. ( 70 V )
12
112710. A rectangular loop with a sliding connector of length
1 = 1.0 m is situated in a uniform magnetic field B –
perpendicular to the plane of loop. Resistance of connect
is r= 2 12. Two resistance of 6 32 and 3 32 are connected
as shown in figure. The external force required to keep the
connector moving with a constant velocity v = 2 m/s is
230
(a) 6N
(c) 2N
(b) 4N
(d) IN
ca
Minolemt
12
1128The magnetic flux through a circuit of resistance ‘R’ changes by an amount
( Delta Phi ) at a time ( Delta t . ) Then the total
quantity of electric charge ( Q ) that passes any point in the circuit during the time ( Delta t ) is represented by
( ^{mathbf{A}} cdot Q=frac{Delta Phi}{R} )
в. ( Q=frac{Delta Phi}{Delta t} )
c. ( Q=R cdot frac{Delta Phi}{Delta t} )
D. ( Q=1 R cdot frac{Delta Phi}{Delta t} )
12
1129energy is converted into
energy by an electric generator.
A. mechanical, mechanical
B. electrical, electrical
c. electrical, mechanical
D. mechanical, electrical
12
1130A uniform magnetic field is restricted
within a region of radius ( r . ) The
magnetic field changes with time at a rate ( frac{d vec{B}}{d t} . ) Loop 1 of radius ( R>r ) enclose the region ( r ) and loop 2 of radius ( R ) is
outside the region of magnetic field as shown in the figure below. Then the
e.m.f. generated is :
( A )
B. Zero in loop 1 and zero in loop 2
c. ( quad frac{d vec{B}}{d t} pi r^{2} ) in loop 1 and ( -frac{d vec{B}}{d t} pi r^{2} ) in loop 2
D. ( -frac{d vec{B}}{d t} pi R^{2} ) in loop 1 and zero in
12
1131The magnetic flux linked with a coil
varies as ( phi=3 t^{2}+4 t+9 . ) what is the
magnitude of the emf at ( t=2 s ? phi ) is in
Wh.
12
1132(AIEEE 2004
8. A metal conductor of length 1 m rotates vertically
one of its ends at an angular velocity 5 radians per
If the horizontal component of the earth’s magnetic field
0.2 x 10-4 T, then the emf developed between the two
ends of the conductor is
(a) 5 uV
(b) 50 uV
(c) 5 mV
(d) 50 mV (AIEEE 2004
12
1133A uniform but time varying magnetic
field ( mathrm{B}=boldsymbol{K}_{1} boldsymbol{K}_{2} boldsymbol{t} ) where ( boldsymbol{K}_{1} & boldsymbol{K}_{2} ) are
positive constants and t is time (in seconds), is applied perpendicular to the plane of a circular loop of radius a and resistance R.Find the total charge (in coulomb) that will pass through any point of the loop by the time ( mathrm{B} )
becomes zero. [Given a ( =2 mathrm{m}, mathrm{R}=pi Omega, K_{1} ) ( =2 T] )
12
1134toppr ( E )
field at ( t=0 ) and completely emerges
out at ( t=T ) sec. The current in the ring
varies as
A.
B.
( c )
D.
12
1135Use Lenz’s law to determine the
direction of induced current in
the situations described by Fig.(a) ( A ) wire of irregular shape turning into a circular shape;(b) A circular loop being
deformed into a narrow straight wire.
12
1136A rectangular loop is placed near a current carrying straight wire as shown in figure. If the loop is rotated about an axis passing through one of its sides, find the direction of induced current in
the loop.
12
velocity ( v ) out of a region of uniform
magnetic field whose magnitude is ( boldsymbol{B} )
The plane of loop and the velocity are both perpendicular to ( vec{B} ). Then the electrical power in the circular loop at the instant when the arc (of circular
loop) outside the region of magnetic field subtends an angle ( frac{pi}{3} ) at centre of
the loop is
( ^{mathrm{A}} cdot frac{B^{2} a^{2} v^{2}}{R} )
B. ( frac{2 B^{2} a^{2} v^{2}}{R} )
c. ( frac{B^{2} a^{2} v^{2}}{2 R} )
D. None of thes
12
1138A conducting rod of mass ( m ) and length
is free to move without friction on two
parallel long conducting rails, as shown below. There is a resistance ( R ) across
the rails. In the entire space around,
there is a uniform magnetic field ( boldsymbol{B} )
normal to the plane of the rod and rails.
The rod is given an impulsive velocity ( boldsymbol{v}_{0} ) Finally, the initial energy ( frac{1}{2} m v_{0}^{2} )
A. Will be converted fully into heat energy in the resistor
B. Will enable rod to continue to move with velocity ( v_{0} )
since the rails are frictionless
c. will be converted fully into magnetic energy due to induced current
D. Will be converted into the work done against the magnetic field
12
1139A rectangular coil is rotated in a uniform magnetic field about an axis passing through its centre and perpendicular to the direction of the field, then the induced voltage in the coil is directly proportional to the:
A. Number of turns in the coil
B. Area of the coil
c. Angular speed of the coil
D. All of these
12
1140Read the following statements and answer whether the given statement is true or false.

The Lenz’s law is consistent with the law
of conservation of energy.
A. True
B. False

12
1141In an AC generator, a coil with ( N ) turns,
all of the same area ( A ) and total
resistance ( boldsymbol{R}, ) rotates with frequency in
a magnetic field ( B ). The maximum
value of emf generated in the coil is:
( mathbf{A} . N . A . B )
в. ( N . A . B . R )
( ^{mathbf{C}} cdot frac{1}{10} N cdot A cdot B )
D. ( frac{1}{10} N . A . B . R )
12
1142Draw a diagram of AC generator and describe it. Derive an expression for instantaneous value of induced emf12
1143In a uniform magnetic field of induction
( B ) a wire in the form of a semicircle of
the circle with angular frequency ( omega . ) the
axis of rotation is perpendicular to the
field. If the total resistance of the circuit
is ( R ) the mean power generated per period of rotation is
A ( cdot frac{B pi r^{2} omega}{2 R} )
B. ( frac{left(B pi r^{2} omegaright)^{2}}{8 R} )
c. ( frac{(B pi r omega)^{2}}{2 R} )
D. ( frac{left(B pi r omega^{2}right)^{2}}{8 R} )
12
1144A rectangular loop of resistance ( mathrm{R} ) and sides I and ( x ) is pulled out of a uniform magnetic field B with a steady velocity
v. The necessary force F required for maintaining uniform velocity of withdrawal is
A. ( B x l^{2} v / R )
B ( cdot B^{2} l^{2} v / R )
c ( cdot B^{2} l^{2} v^{2} / R )
D. zero
12
1145According to which law current ( boldsymbol{I} ) flowing in the rod must vary for the rod to rotate at a constant angular speed. Begin to measure the time from the instant when the rod is in its right-hand horizontal position. Consider the current to be positive when it flows from the axis of rotation toward the ring.12
1146A magnet is moved towards a coil (i) quickly (ii) slowly, then the induced e.m.f. is
A. larger in case (i)
B. smaller in case (i)
c. equal in both the cases
D. larger or smaller depending upon the radius of the coil
12
1147The number of turns in an air core
solenoid of length ( 25 mathrm{cm} ) and radius 4 ( mathrm{cm} ) is ( 100 . ) Its self inductance will be
A ( cdot 5 times 10^{-4} H )
в. ( 2.5 times 10^{-4} H )
c. ( 5.4 times 10^{-3} H )
D . ( 2.5 times 10^{-3} mathrm{H} )
12
1148Interpret ( mathrm{K}^{prime}-mathrm{K} )12
1149op
direction. The number of turns is ( n ) and
the cross sectional area of the coil is ( A )
When the coil turns through ( 180^{circ} ) about
its diameter, the charge flowing through the coil is ( Q ). The total
resistance of the circuit is ( R ). What is
the magnitude of the magnetic
induction?
( ^{A} cdot frac{Q R}{n A} )
в. ( frac{2 Q R}{n A} )
c. ( frac{Q n}{2 R A} )
D. ( frac{Q R}{2 n A} )
12
1150An a.c of ( 50 H z ) and ( 1 A ) peak value flow
in the primary coil of a transformer. The mutual inductance between primary
and secondary coils is ( 1.5 H . ) Then peak value of induced emf across secondary coil is
A. ( 75 pi ) volt
B . ( 150 pi ) volt
c. 225 volt
D. 300volt
12
1151Consider a circular coil of wire carrying
constant current I, forming a magnetic dipole. The magnetic flux through an infinite plane contains the circular coil and excluding the circular coil area is
given by ( mathbf{Phi}_{mathbf{i}} . ) The magnetic flux through
the area of the circular coil area is given
by ( mathbf{Phi}_{mathbf{0}} )
Which of the following options is
correct?
( mathbf{A} cdot Phi_{mathrm{i}}Phi_{0} )
( mathbf{D} cdot Phi_{mathrm{i}}=-Phi_{0} )
12
1152A step down transformer has 50 turns
on secondary and 1000 turns on primary winding. If a transformer is connected
to ( 220 V, 1 A ) A.C. source, what is output
current of the transformer?
A ( cdot frac{1}{20} A )
B. 20 A
( c cdot 100 A )
D. 2 A
12
1153What is self inductance? Establish
expression for self inductance of a long Solenoid.
12
1154How as a scimilicic un raurus
( a, ) is rotating about an axis ( P Q ) with a
constant angular velocity ( omega=1 / sqrt{L C} )
with the help of an external agent. ( mathbf{A} )
uniform magnetic field ( B ) exists in
space and is directed into the plane of the figure. (circuit part remains at rest)
(left part is at rest)
This question has multiple correct options
A the rms value of current in the circuit is ( frac{pi B a^{2}}{R sqrt{2 L C}} )
B. The rms value of current in the circuit is ( frac{pi B a^{2}}{2 R sqrt{2 L C}} )
C. The maximum energy stored in the capacitor is ( frac{pi^{2} B^{2} a^{4}}{8 R^{2} C} )
D. The maximum power delivered by the external agent is ( frac{pi^{2} B^{2} a^{4}}{4 L C R} )
12
1155A circular loop of radius ( boldsymbol{R} ), carrying
current ( I, ) lies in ( x ) -y plane with its
center at origin. The total magnetic flux through x-y plane is
A. directly proportional to ( I )
B. directly proportional to ( R )
c. inversely proportional to ( R )
D. inversely proportional to ( I )
E. zero
12
1156Alternating current is flowing in inductance ( L ) and resistance ( R ). The
frequency of source is ( frac{omega}{2 pi} . ) Which of the
following statement is correct.
A. For low frequency the limiting value of impedance is ( L )
B. For high frequency the limiting value of impedance is ( L omega )
C. For high frequency the limiting value of impedance is ( R )
D. For low frequency the limiting value of impedance is ( L omega )
12
1157The emf induced between ( M ) and ( Q ) if
the potential between ( P ) and ( Q ) is ( 100 V )
( M ) is midpoint of ( boldsymbol{P} ) and ( boldsymbol{Q} )
A . ( 25 V )
в. ( 50 V )
( c .75 V )
D. ( 100 V )
12
1158If the resistance of the upper half of a
rigid loop is twice of that of the lower
half, the magnitude of magnetic
induction at the centre is equal to:
A. zero
B. ( frac{mu_{0} I}{4 a} )
c. ( frac{mu_{0} I}{12} )
D. None of these
12
1159Draw a neat diagram of ( A C ) dynamo
and label the parts.
12
1160The potential difference across a ( 150 m H ) inductor as a function of time
is shown in figure. Assume that the initial value of the current in the
inductor is zero. What is the current
when ( t=4.0 m s ? )
A ( cdot 2.67 times 10^{-4} mathrm{A} )
B ( cdot 3.67 times 10^{-2} mathrm{A} )
( c cdot 6.67 times 10^{-2} mathrm{A} )
D. ( 9.67 times 10^{-4} mathrm{A} )
12
1161In a coil of resistance ( 100 Omega ), a current is
induced by changing the magnetic flux through it as shown in the figure. The
magnitude of change in flux through
the coil is :
A. ( 275 mathrm{Wb} )
в. ( 200 mathrm{Wb} )
( c cdot 225 W b )
D. ( 250 mathrm{Wb} )
12
1162( A B ) and ( C D ) are smooth, parallel, horizontal rails on which a conductor ( T )
can slide. A cell, E, drives current
through the rails and ( T )

This question has multiple correct options
A. The current in the rails will set up a magnetic field ove
B. T will experience a force to the right
C. ( T ) will experience a force to the left
D. Twill not experience any force

12
1163Self inductance of a long solenoid is directly proportional to ( (N ) is no. of turns in solenoid)
A . ( N )
B . ( N^{2} )
( c cdot 1 / N )
D. ( 1 / N^{2} )
12
1164( Q ) тур
When the fan runs at full speed, its speed becomes constant. This is because the torque due to magnetic field inside the fan is balanced by the torque due to air resistance on the
blades of the fan and the torque due to friction between the fixed part and the shaft of the fan. The electric power going into the fan is spent (i) in the internal resistance as heat, call it ( P_{1}, ) (ii) in doing work against internal friction and air resistance producing heat, sound,
etc., call it ( P_{2} ). When the coil of fan
rotates, an emf is also induced in the coil. This opposes the external emf is also induced in the coil. This opposes
the external emf applied to send the current to the fan. This emf is called
back emf, call it ( e . ) Answer the following questions when the fan is running at full speed.The current flowing into the
fan and the value of back emf ( e ) is
A. ( 200 A, 5 V )
B . ( 5 A, 200 V )
c. ( 5 A, 195 V )
D. ( 1 A, 0 V )
12
1165A coil of area ( 500 mathrm{cm}^{2} ) having 1000 turns
is placed such that the plane of the coil is perpendicular to a magnetic field of magnitude ( 410^{-5} )weber ( / m^{2} ). If it is
rotated by 180 degree about an axis passing through one of its diameter in
( 0.1 mathrm{sec}, ) find the average induced emf.
A. zero
в. ( 30 m V )
( mathrm{c} .40 mathrm{mV} )
( mathbf{D} .50 mathrm{mV} )
12
1166Two coils each of self-inductance ( L ) are
connected in parallel. It they are separated by a large distance, then what will be the self-inductance of
combination?
A ( cdot frac{L}{4} )
в. ( frac{L}{2} )
( c . L )
D. ( 2 L )
12
1167A coil in a simple generator has 200 turns.Now the number of turns in the
coil increases to ( 500 . ) What will be its
effect:
A. current produced will increase
B. voltage produced will increase
( c cdot ) both
D. none
12
1168What is the highest generated power?
( ^{mathbf{A}} cdot P_{max }=frac{v^{2} B^{2} d}{4 rho S} )
B. ( quad P_{max }=frac{v^{2} B^{2} S d}{4 rho} )
( ^{mathrm{C}} P_{max }=frac{v^{2} B^{2} S d}{rho} )
D ( quad P_{max }=frac{v^{2} B^{2} S d}{2 rho} )
12
1169Derive the expression for the motional
emf induced in a conductor moving in a uniform magnetic field.
12
1170A magnetic field of ( 2 times 10^{-2} T ) acts at
right angles to a coil of area ( 100 mathrm{cm}^{2} )
with 50 turns. The average emf induced in the coil is ( 0.1 V . ) When it is removed
from the field in ( t ) second, the value of ( t )
is
A . ( 10 s )
B. ( 0.1 s )
c. ( 0.01 s )
D. ( 1 s )
12
1171A current in a 240 turn solenoid varies
at ( 0.8 A / s . ) Find emf induced if the
length of the solenoid is ( 12 mathrm{cm} ) and
radius ( 2 c m )
A ( cdot 6.14 times 10^{-4} V )
в. ( 6.4 times 10^{-3} V )
( mathrm{c} .3 .07 times 10^{-3} mathrm{V} )
D. ( 3.07 times 10^{-4} V )
12
1172Find the terminal velocity of the
connector?
12
1173A thick strip of copper is mounted as a compound pendulum about O.If it is made to swing through a uniform magnetic field B normal to the plane of the strip then (neglecting air resistance) it is found that
A. strip swings almost freely.
B. motion of the strip is heavily damped.
c. strip does not oscillate at all but immediately comes to rest in the vertical position
D. strip swings almost freely but its temperature decreases
12
1174angled isosceles triangle of height
( 10 mathrm{cm} ) is kept such that the ( 90^{circ} ) vertex
is very close to an infinitely long
conducting wire (see the figure). The
wire is electricity insulted from the loop
The hypotenuse of the triangle is parallel to the wire. The current in the
triangle loop is in counterclockwise
direction and increased at a constant
rate of ( 10 A s^{-1} . ) Which of the following
statement(s) is(are) true?
This question has multiple correct options
A cdot The magnitude of induced emf in the wire is ( left(frac{mu_{0}}{pi}right) ) volt
B. If the loop is rotated at a constant angular speed about the wire, an additional emf of ( left(frac{mu_{0}}{pi}right) )
C. The induced current in the wire is in opposite direction to the current along the hypotenuse
D. There is a repulsive force between the wire and the loop
12
1175The motion of copper plate is damped
when it is allowed to oscillate between
the two poles of a magnet. What is the cause of this damping?
12
1176Explain seld induction and mutual
induction.
12
1177toppr
( A )
B
( c )
( D )
12
1178The coefficients of self induction of two
coils are ( L_{1}=8 mathrm{mH} ) and ( L_{2}=2 mathrm{mH} )
respectively. The current rises in the two coils at the same rate. The power given to the two coils at any instant is same. The ratio of induced emf’s in the coils
will be :
A. ( frac{V_{1}}{V_{2}}=4 )
B. ( frac{V_{1}}{V_{2}}=frac{1}{4} )
c. ( frac{V_{1}}{V_{2}}=frac{1}{2} )
D. ( frac{V_{1}}{V_{2}}=frac{1}{3} )
12
1179A conducting loop in the shape of a right angled isosceles triangle of height
( 10 mathrm{cm} ) is kept such that the ( 90^{circ} ) vertex
is very close to an infinitely long conducting wire (see the figure). The wire is electrically insulated from the loop. The hypotenuse of the triangle is parallel to the wire. The current in the triangular loop is in counter clockwise direction and increased at a constant
rate of ( 10 A s^{-1} . ) Which of the following
statement (s) is (are) true?
This question has multiple correct options
A. There is a repulsive force between the wire and the loo
B. If the loop is rotated at a constant angular speed about the wire, an additional emf of ( left(frac{mu_{0}}{pi}right) ) volt is induced in the wire
C . The magnitude of induced emf in the wire is ( left(frac{mu_{0}}{pi}right) ) vo
duced current in the wire is in opposite directic to the current along the hypo
12
1180Direction of current in the loop at ( t= )
( frac{pi}{3 omega} )
( A ). clockwise
B. anticlockwise
c. no current will flow at that time
D. cannot be determined
12
1181A current ( l ) is flowing in a straight
conductor of length ( L ). The magnetic
induction at a point on its axis at a
distance ( frac{L}{4} ) from its centre will be
A . zero
в. ( frac{mu_{0} l}{2 pi L} )
c. ( frac{mu_{0} l}{sqrt{2} L} )
D. ( frac{4 mu_{0} l}{sqrt{5} pi L} )
12
1182An airplane in which the distance
between the tips of the wings is 50 meter is flying horizontally with a speed of 360 km/hour over a place where the vertical
component of earths magnetic field is ( 2.0 times 10^{-4} ) Testa. The potential difference
between the tips of the wings would be:-
A . 0.1
B. 1.0
c. ( 0.2 v )
D. ( 0.0 mathrm{v} )
12
1183Assertion
Eddy currents in conductors of non-zero resistivity generate heat as well as electromagnetic forces.
Reason
Current is always associated with heat
and electromagnetic forces
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
1184100
101
11. A small square loop of wire of side lis placed inside a large
square loop of wire of side L (L > I).
The loop are coplanar and their centre
coincide. The mutual inductance of the i
system is proportional to
(a) UL
(b) BIL
(c) L/I
(d) L?I1
12
1185What is self inductance? Name the
factors on which self inductance
depends.
12
1186Assertion(A): An inductor in a D.C.
circuit opposes both a steady current and a changing current. Reason(R): Induced emf is generated
only when the flux linked with the inductor remains unchanged.
A. Both A and R are individually true and R is the correct explanation of A
B. Both A and R are individually true but R is not the correct explanation of ( A )
c. A is true but R is false
D. Both A and R are false
12
1187A square of side L meters lies in the ( x-y ) plane in a region, where the magnetic field given by ( vec{B}=B_{o}(2 hat{i}+3 hat{j}+4 hat{k}) T )
where ( B_{o} ) is constant. The magnitude of flux passing through the square is :
B. ( 3 B_{o} L^{2} W b )
( mathbf{c} cdot 4 B_{o} L^{2} W b )
D. ( sqrt{29} B_{o} L^{2} W b )
12
1188An emf is induced in an aeroplane
during its ascent and descent in east-
west direction due to
A. The horizontal component of the earth’s magnetic field
B. The vertical component of the earth’s magnetic field
c. Both 1 and 2
D. None of the above
12
1189If a current increases from zero to one
ampere in 0.1 second in a coil of ( 5 mathrm{mH} )
then the magnitude of the induced e.m.f. will be
A . 0.005 volt
B. 0.5 volt
c. 0.05 volt
D. 5 volt
12
1190Which of the following units denotes the dimensions ( M L^{2} / Q^{2}, ) where ( Q ) denotes the electric charge?
A. Weber (Wb)
в. ( W b / mathrm{m}^{2} )
c. Henry ( (H) )
D. H / m ( ^{2} )
12
1191A glass rod of length ( ell ) moves with a velocity ( v ) in a uniform magnetic field ( B )
what will be the emf induced in the rod:
A . ( B l v )
в. ( frac{B l}{v} )
c. ( B l )
D. None of these
12
1192An inductor with an inductance of
( 3.00 H ) and a resistance of ( 7.00 Omega ) is
connected to the terminals of a battery
with an emf of ( 12.0 mathrm{V} ) and negligible
internal resistance. Find the initial rate
of increase of current in the circuit.
12
1193A circular coil of mean radius of ( 7 mathrm{cm} )
and having 4000 tums is rotated at the rate of 1800 revolutions per minute in the earth’s magnetic field ( (mathrm{B}=0.5 ) Gauss ), The peak value of emf induced is
A . ( 1.158 mathrm{v} )
B. 0. 58 v
c. ( 0.29 v )
D. 5.8
12
1194A wheel with 10 metallic spokes each
( 0.5 m ) long is rotated with a speed of
120rev/min in a plane normal to the horizontal component of earth’s
magnetic field ( boldsymbol{H}_{boldsymbol{E}} ) at a place.lf ( boldsymbol{H}_{boldsymbol{E}}= )
( 0.4 G ) at the place, what is the induced
emf between the axle and the rim of the
wheel? Note that ( 1 G=10^{-4} )
12
1195In A.C generator increasing no. of turns
in coil :
A. decreases the EMF
B. EMF remains same
c. increases the EMF
D. EMF becomes zero
12
1196A field of strength ( frac{mathbf{5} times mathbf{1 0}^{mathbf{4}}}{boldsymbol{pi}} ) ampere
turns /meter acts at right angles to a coil of 50 turns of area ( 10^{-2} m^{2} . ) The coil
is removed from the field in 0.1 second.
Then, the induced e.m.f in the coil is:
A . ( 0.1 mathrm{v} )
B. 0.2 ( v )
c. ( 1.96 v )
D. 0.98
12
1197In an AC generator, maximum number
of lines of force pass though the coil when the angle between the plane of coil and lines of force is :
A ( cdot 0^{circ} )
B. 60
( c cdot 30 )
D. ( 90^{circ} )
12
1198When the coil and the magnet are both stationary
A. there is no deflection in the galvanometer.
B. galvanometer deflects
c. galvanometer bursts.
D. none
12
1199Draw a labelled diagram of a simple a.c.
generator.
12
1200Magnetic flux ( phi ), in weber, in a closed
circuit of resistance ( 10 Omega ) varies with
time ( t ) in seconds as ( phi=6 t^{2}-5 t+1 )
The magnitude of induced current at
( t=0.25 s ) is :
A. ( 0.2 mathrm{A} )
B. 0.6 ( A )
( c cdot 1.2 A )
D. ( 0.8 mathrm{A} )
12
120130. A vertical conducting ring of radius R falls vertically wil
a speed Vin a horizontal uniform mag-
netic field B which is perpendicular to
the plane of the ring. Which of the fol-
lowing statements is correct?
(a) A and B are at the same potential
(b) C and D are at the same potential
(c) current flows in clockwise direction
(d) current flows in anticlockwise direction
12
1202A magnetic field is directed normally
downwards through a magnetic frame
as shown in the figure. On increasing
the magnetic field:
begin{tabular}{r|rrrrr}
( 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 ) \
hline
end{tabular}
[
times times times times times times
]
A. plate B will be positively charged
B. plate A will be positively charged
C. none of the plates will be positively charged
D. all of the above
12
1203In the following figure the bulb will start
lighting suddenly if :
A. Key is closed
B. Key is opened
C. Key is either closed or opened
D. Nothing is done
12
1204A horizontal telegraph wire ( 0.5 k m ) long
running east and west in a part of a circuit whose resistance is ( 2.5 Omega ). The
wire falls to ( g=10.0 m / s^{2} ) and ( B= )
( 2 times 10^{-5} w e b e r / m^{2}, ) then the current
induced in the circuit is
A. 0.7 amp
B. 0.04 amp
c. 0.02 amp
D. ( 0.01 a m p )
12
1205A charge particle having mass ( mathrm{m} ) and charge ( +boldsymbol{q}, ) given a velocity ( overrightarrow{boldsymbol{V}}_{0}=mathbf{2} overline{boldsymbol{i}}+ )
( 4 j m / s ) in a region where electric field
and magnetic field exists. Magnetic field in the region is ( vec{B}=6 bar{i}-8 bar{j} ) (Tesla). It is observed of charged particle remains constant. Electric field in the region is:
A. ( 50 N / C )
в. ( 40 N / C )
c. ( 30 N / C )
D. ( 60 N / C )
12
1206A metal ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The magnet falls with an acceleration:
A. Equal to ( g )
B. Less than ( g )
c. Greater than ( g )
( D . ) none
12
1207The magnetic field in a certain region is given by ( vec{B}=(4.0 hat{i}-1.8 hat{k}) times 10^{-3} T )
How much flux passes through a ( 5.0 mathrm{cm}^{2} ) area loop in this region if the
loop lies flat on the ( x-y ) plane?
A ( cdot 8 times 10^{-5} mathrm{Wb} )
B . ( 3 times 10^{-5} mathrm{Wb} )
c. ( 9 times 10^{-7} W b )
D. ( 3 times 10^{-7} mathrm{Wb} )
12
1208A rectangular frame of wire abcd has
dimensions ( 32 mathrm{cm} times 8.0 mathrm{cm} ) and a total
resistance of ( 2.0 Omega . ) It is pulled out of a
magnetic field ( B=0.020 T ) by applying
a force of ( 3.2 times 10^{-5} N ) (figure). It is
found that the frame moves with
constant speed. Find the emf induced in
the loop.
12
1209A very small circular loop of radius ( a ) is
initially ( (a t t=0) ) coplanar and
concentric with a much larger fixed
circular loop of radius ( b ). A constant
current ( I ) flows in the larger loop. The smaller loop is rotated with a constant
angular speed ( omega ) about the common diameter. The emf induced in the
smaller loop as a function of time ( t ) is:
( ^{mathbf{A}} cdot frac{pi a^{2} mu_{0} I}{2 b} omega cos (omega t) )
в. ( frac{pi a^{2} mu_{0} I}{2 b} omega sin left(omega^{2} t^{2}right) )
( ^{text {c. }} frac{pi a^{2} mu_{0} I}{2 b} omega sin (omega t) )
D ( cdot frac{pi a^{2} mu_{0} I}{2 b} omega sin ^{2}(omega t) )
12
1210A disc of radius ( R ) is rolling without sliding on a horizontal surface with a velocity of center of mass ( v ) and angular
velocity ( omega ) in a uniform magnetic field ( B ) which is perpendicular to the plane of
the disc as shown in figure. ( O ) is the
center of the disc and ( P, Q, R ) and ( S ) are
the four points on the disc. Which of the
following statements is true?
This question has multiple correct options
A. Due to translation, induced emf across ( P S=B v r )
B. Due to rotation, induced emf across ( Q S=0 )
c. Due to translation, induced emf across ( R O=0 )
D. Due to rotation, induced emf across ( O Q=B v r )
12
1211The current produced in a generator
armature is AC because
A. the magnetic field reverses at intervals
B. The current in the field coils is AC
C. the rotation of the armature causes the field through it to reverse
D. the commutator feeds current into it in opposite directions every half cycle
12
1212A ( 50 ~ m H ) coil carries a current of ( 2 A )
The energy stored in joule is
A . ( 0 . )
B. 0.5
c. ( 1 . )
D. 5.0
12
1213A coil of 1200 turns and mean area of
( 500 mathrm{cm}^{2} ) is held perpendicular to a uniform magnetic field of induction
( 4 times 10^{-4} mathrm{T} . ) The resistance of the coil is
20 ohms. When the coil is rotated
through ( 180^{0} ) in the magnetic field in 0.1
s, the average electric current (in ( mathrm{mA} ) ) induced is :
A ( cdot 12 )
B. 24
( c . ) 36
D. 48
12
1214A solenoid of self-inductance ( 1.2 H ) is in
series with a tangent galvanometer of reduction factor ( 0.9 A ). They are connected to a battery and the tangent
galvanometer shows a deflection of ( 53^{circ} )
The energy stored in the magnetic field of the solenoid is:
( left(tan 53^{circ}=4 / 3right) )
begin{tabular}{l}
A. 0.8645 \
hline
end{tabular}
в. ( 0.72 J )
c. ( 0.173 J )
D. ( 1.44 J )
12
1215The magnetic flux linked with a coil, in webers, is given by the equation ( phi= )
( 8 t^{2}-3 t+5 . ) Then the magnitude of
induced emf at 4 sec will be
A . 15 v
B . ( -61 mathrm{v} )
c. 13 v
D. 21 v
12
1216The coil is wound on an iron core and
looped back on itself so that core has two sets of closely wound coils carrying current in opposite directions. The self inductance is
( A cdot 0 )
B. ( 2 L )
( mathrm{c} cdot 2 mathrm{L}+mathrm{M} )
D. ( L+2 M )
12
1217A long copper wire contains a current
of I ampere. The magnetic flux per
metre of the wire for a plane surface inside the wire as shown in figure.
( ^{A} cdot frac{mu_{0}}{2 pi} )
В ( frac{mu_{0}}{4 pi} )
c. ( frac{mu_{0}}{pi} )
D. ( frac{mu_{0}}{6 pi} )
12
1218The length of a wire required to
manufacture a solenoid of length ( l ) and
self-induction ( L ) is (cross-sectional
area is negligible)
A ( cdot sqrt{frac{2 pi L l}{mu_{0}}} )
в. ( sqrt{frac{mu_{0} L l}{4 pi}} )
c. ( sqrt{frac{4 pi L l}{mu_{0}}} )
D. ( sqrt{frac{mu_{0} L l}{2 pi}} )
12
1219A copper rod of length ‘I’ rotates at an
angular velocity ‘ ( omega^{prime} ) in a uniform magnetic field B as shown in figure. What is the induced emf across its
ends?
12
1220What is the relationship between an electric current and a magnetic field?12
1221A semicircle loop ( P Q ) of radius ( ^{prime} R^{prime} ) is
moved with velocity ( ^{prime} v^{prime} ) in transverse
magnetic field as shown in figure. The
value of induced emf. at the end of loop
is :-
12
1222A circular loop of wire is in the same
place as an infinitely long wire carrying a constant current i. Four possible motion of the loop are marked by ( mathrm{N}, mathrm{E}, mathrm{W} )
and ( mathrm{S} ) as shown.
A clockwise current is induced in the
loop when loop is pulled towards
( A )
B.
( c cdot w )
( D )
12
1223Change in number of magnetic field
lines induces
A. current in coil
B. EMF in the coil
c. frequency in coil
D. both A and C
12
1224A plane electromagnetic wave in a non magnetic dielectric medium is given by ( overline{boldsymbol{E}}=overline{boldsymbol{E}}_{0}left(mathbf{4} times mathbf{1 0}^{-mathbf{7}} boldsymbol{x}-mathbf{5 0} boldsymbol{t}right) ) with
distance being in meter and time in seconds. The dielectric constant of the
medium is:
A . 5.8
B. 2.4
c. 1.6
D. 3.5
12
1225The magnetic flux linked with a coil,in webers,is given by the equations ( phi= )
( 3 t^{2}+4 t+9 . ) Then the magnitude of
induced e. ( mathrm{m} ). ( mathrm{f} ). at ( mathrm{t}=2 ) second will be:
A . 2 volt
B. 4 volt
c. 8 volt
D. 16 volt
12
1226The phenomenon of producing an emf in a circuit whenever the magnetic flux linked with a coil changes is
A. Electro-magnetic induction
B. Inducing current
c. Inducing voltage
D. change in current
12
1227A fighter plane of length ( 20 mathrm{m}, ) wing span (distance from tip of one wing to the tip of the other wing) of ( 15 mathrm{m} ) and height ( 5 mathrm{m} ) is flying towards east over Delhi. Its speed is ( 240 m s^{-1} ). The earth’s
magnetic field over Delhi is ( 5 times 10^{-5} mathrm{T} )
with the declination angle ( sim 0^{circ} ) and dip
of ( theta ) such that ( sin theta=frac{2}{3} . ) If the voltage
developed is ( V_{B} ) between the lower and
upper side of the plane and ( V_{W} ) between
the tips of the wings then ( V_{B} ) and ( V_{W} )
are close to
A ( cdot V_{B}=40 m V ; V_{W}=135 mathrm{mV} ) with left side of pilot at
higher voltage
B . ( V_{B}=45 mathrm{mV} ; V_{W}=120 mathrm{mV} ) with right side of pilot at
higher voltage
C. ( V_{B}=40 mathrm{mV} ; V_{W}=135 mathrm{mV} ) with right side of pilot at high voltage
D. ( V_{B}=45 mathrm{mV} ; V_{W}=120 mathrm{mV} ) with left side of pilot at
higher voltage
12
1228The circuit diagram shows that resistors ( 2 Omega, 4 Omega ) and ( R Omega ) connected to
a battery of e.m.f. 2 V and
internal resistance ( 3 Omega ). A main
current of 0.25 A flows through the
circuit. The p.d. across the internal
resistance of the cell is :
A . ( 0.75 mathrm{v} )
B. 2
( c cdot 0.5 v )
0.11
12
1229The flux of magnetic field through closed conducting loop of resistance 0.4 Whanges with time according to the
equation ( phi=0.20 t^{2}+0.40 t+0.60 ) where
is time in seconds. Find
(i) the induced
emf at ( t=2 s . ) (ii) the average induced emf in ( t=0 ) to ( t=5 ) s. (iii) change passed through the loop in ( t=0 ) to ( t=5 s . ) (iv) average current in time interval ( t=0 ) to
( t=5 s )
(v) heat produced in ( t=0 ) to ( t=5 s )
12
1230Describe the principal, construction and working of a single-phase ( A C ) generator12
1231AC generator is also h/a
A. convertor
B. invertor
c. alternator
D. none
12
1232An aeroplane is moving towards north horizontally with a speed of ( 200 mathrm{m} / mathrm{s} ) at a
place where the vertical component of earths magnetic field is ( 0.5 times 10^{-4} ) tesla.
Then the induced e.m.f. set up between the tips of the wings of the plane if they are ( 10 m ) apart is:
A. 0.1 volt
B. 0.01 volt
c. 10 volt
D. 1 volt
12
1233A conducting loop in the shape of a right angled isosceles triangle of height
( 10 mathrm{cm} ) is kept such that the ( 90^{circ} ) vertex
is very close to an infinitely long conducting wire (see the figure). The wire is electrically insulated from the loop. The hypotenuse of the triangle is parallel to the wire. The current in the triangular loop is in counter clockwise direction and increased at a constant
rate of ( 10 A s^{-1} . ) Which of the following
statement (s) is (are) true?
This question has multiple correct options
A. There is a repulsive force between the wire and the loo
B. If the loop is rotated at a constant angular speed about the wire, an additional emf of ( left(frac{mu_{0}}{pi}right) ) volt is induced in the wire
C . The magnitude of induced emf in the wire is ( left(frac{mu_{0}}{pi}right) ) vo
duced current in the wire is in opposite directic to the current along the hypo
12
shown in figure are connected at one
end to a charged capacitor through a
switch ( S, ) which initially open. At the
other end, they are connected by a loose
wire. The capacitor has charge ( Q ) and
mass per unit length of the rod is ( lambda ). The
effective resistance of the circuit after
closing the switch is ( R ). If the velocity of
each rod when the capacitor is discharged after closing the switch is ( boldsymbol{v}=frac{boldsymbol{mu}_{0} boldsymbol{Q}^{2}}{boldsymbol{x} pi boldsymbol{d} boldsymbol{R} boldsymbol{lambda} boldsymbol{l}} . ) Find ( boldsymbol{x} )
(Assume that the displacement of rods during the discharging time is
negligible)
12
1235Magnetic flux linked with a coil is ( phi= ) ( 5 t^{2}+2 t+3, ) where ( t ) is second and ( phi ) is
in weber. At time ( t=1 ) s, the value of induced emf is volt
A . 14
B. 1.
c. 12
D. 6
12
1236When a rectangular coil is rotated in a uniform magnetic field about an axis passing through its centre and perpendicular to the field, the emf induced in the coil varies:
A. Linearly
B. Exponentially
c. sinusoidally
D. None of these
12
1237A magnetic field of flux density ( 1.0 mathrm{Wb} )
( m^{-2} ) acts normal to a 80 tum coil of 0.01
( m^{2} ) area. The e.m.f. induced in it, if this coil is removed from the field in 0.1
second is :
( A cdot 8 v )
B. ( 4 v )
c. ( 10 v )
D. ( 6 v )
12
1238A wheel with 10 metallic spokes each ( 0.5 mathrm{m} ) long is rotated with a speed of 120 rev/min in a plane normal to the earth’s magnetic field at the place.lf the magnetic of the field is ( 0.4 mathrm{G} ), what is the induced emf between the axle and the
rim of the wheel?
12
1239Plane of both loops circle and ellipse are held perpendicularly to the uniform magnetic field of strength B, Compare the magnetic flux passing through both
loops if ( phi_{c}, ) the magnetic flux through
the circular loop and ( phi_{E}, ) the magnetic
flux through the elliptical loop given
that area of both loops are same.
( mathbf{A} cdot phi_{c}=2.5 phi_{E} )
B ( cdot phi_{c}=sqrt{2.5} )
( mathbf{c} cdot phi_{c}=phi_{E} )
( mathbf{D} cdot phi_{E}=sqrt{2.5} phi_{c} )
E ( cdot phi_{E}=2.5 phi_{c} )
12
124019. A rod Po is connected to the capacitor plates. The most
placed in a magnetic field (B) B
directed downward
perpendicular to the plane of
3
the paper, If the rod is pulled
out of magnetic field with
velocity v as shown in figure,
(a) Plate M will be positively charged,
(b) Plate N will be positively charged,
(c) Both plates will be similarly charged.
(d) No charge will be collected on plates,
12
1241x
x
ILLUSTRATION 23.2 An angle ZAOB made of a conducting
wire moves along its bisector through a magnetic field B as
suggested by figure. Find the emf induced between the two
free ends if the magnetic field is perpendicular to the plane at
the angle.
x x x x x x x
x x x x x x x x
x x x x x x x
Көx x x x x x
8 x x x x x x
x x x x x
xxx x x x x
B
x x x x x x x x
x
x
x
0
От

х
X
x
x
x
+
x
x
X

x
+
x
x
X
Solution The rod 04 is equivalent to
batter of emf Bl sin

12
1242A coil of radius ( R ) carries current ( I ).
Another concentric coil of radius ( r(r< ) ( <R) ) carries current ( i . ) Planes of two
coils are mutually perpendicular and both the coil are free to rotate about
common diameter. Find the maximum
kinetic energy of the smaller coil when both the coils are released. Masses of
coils are ( M ) and ( m, ) respectively.
12
1243A square-shaped wire loop of mass ( m )
resistance ( boldsymbol{R} ) and side a moving with
speed ( v_{0}, ) parallel to the ( x ) -axis, enters a
region of uniform magnetic field ( B ) which is perpendicular to the plane of the loop. The speed of the loop changes with distance ( x(x<a) ) in the field, as
A ( cdot v_{0}-frac{B^{2} a^{2}}{R m} x )
B. ( _{v_{0}-frac{B^{2} a^{2}}{2 R m} x} )
c. ( _{v_{0}+} frac{B^{2} a}{R m} x )
D. ( v )
12
1244An alternating current generator has an
internal resistance ( boldsymbol{R}_{boldsymbol{g}} ) and an internal
reactance ( X_{g} . ) It is used to supply power to a passive load consisting of a
resistance ( boldsymbol{R}_{g} ) and a reactance ( boldsymbol{X}_{boldsymbol{L}} . ) For maximum power to be delivered from the generator to the load, the value of
( X_{L} ) is equal to
A . zero
в. ( X_{g} )
c. ( -x_{g} )
D. ( R_{g} )
12
1245ILLUSTRATION 24.5 The potential difference E and current I
flowing through the ac circuit is given by E = 5 cos(ot – Tc/6)
V and I = 10 sin or A. Find the average power dissipated in the
circuit.
12
124618. A horizontal ring of radius r = 1/2 m is kept in a vertical
constant magnetic field 1 T. The ring is collapsed from
maximum area to zero area in 1 s. Then the emf induced
in the ring is
(a) 1V
(b) (Tc/4) V
(c) (1/2) V
(d) TV
12
1247Which one of the following statements
is true?
A. A motor works on the principle of electromagnetic induction
B. An electric motor converts mechanical energy into electrical energy
C. AC generator has slip rings while DC generator has a commutator
D. An electric generator converts electrical energy into mechanical energy
12
1248ì iuur 0
( 10^{-2} m^{2} ) which has inductance ( L= )
10m ( H ) and negligible resistance is
placed in a time-varying magnetic field.
Figure shows the variation of B with
time for the interval of 4 s. The field is
perpendicular to the plane of the loop (given at ( t=0, B=0, I=0) . ) The value
of the maximum current induced in the
loop is :
( mathbf{A} cdot 0.1 mathrm{mA} )
B. ( 10 mathrm{mA} )
C. ( 100 mathrm{mA} )
D. Data insufficient
12
1249Multiple Correct Answers Type The Sl unit of inductance, henry, can be
written as
This question has multiple correct options
A. Weber/ampere
B. Volt-second / ampere
c. Joule/(ampere) ( ^{2} )
D. Ohm-second
12
1250A rectangular loop with a slide wire of
length ( l ) is kept in a uniform magnetic
field as shown in figure (a). The
resistance of slider is ( boldsymbol{R} ). Neglecting self
inductance of the loop find the current
in the connector during its motion with
a velocity ( boldsymbol{v} )
( (b) )
A ( cdot frac{B l v}{R_{1}+R_{2}+R} )
B. ( frac{B l vleft(R_{1}+R_{2}right)}{Rleft(R_{1}+R_{2}right)} )
c. ( frac{B l vleft(R_{1}+R_{2}right)}{R R_{1}+R R_{2}+R_{1} R_{2}} )
D ( cdot operatorname{Blv}left(frac{1}{R_{1}}+frac{1}{R_{2}}+frac{1}{R_{3}}right) )
12
1251A magnetic field of flux density 10 T acts normal to a coil of 50 turns having 100 em-area. The e.m.f. induced if the coil is
removed from magnetic field in ( 0 . ) second is:
A. ( 50 v )
B. 60V
( c cdot 80 v )
D. 40v
12

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