Electric Current And Its Effect Questions

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Electric Current And Its Effect Questions

List of electric current and its effect Questions

Question NoQuestionsClass
1Fuse should be connected to ( ldots . . ) wire of
the circuit
A. Earth
B. Neutral
c. Phase
D. Any of the above
7
2Determine the current flowing through the circuit shown above
A . ( 25 mathrm{mA} )
B. ( 12.5 mathrm{mA} )
( c .29 mathrm{mA} )
D. ( 80 mathrm{mA} )
7
3The rating of a fuse connected in the general household lighting circuit is:
( A cdot 15 mathrm{A} )
B. 5 A
( c cdot 10 A )
D. zero
7
4Correct the underline part of the
following statements appropriately if it
is wrong.

The ampearage of the fuse wire must be reduced as the power of the equipment included in the circuit is increased.

7
5When does a fuse cut off current? How
does it do it?
7
6The diagram in Fig. shows a three-pin
socket marked as 1,2 and ( 3 . ) To which wire is the fuse connected?
4
( c )
D. 1 and 3
7
7(i) What happens to the resistivity of semi-conductors with the increase of
temperature?
(ii) For a fuse, higher the current rating is the fuse wire. (Thicker / Thinner)
7
8The diode used in the circuit shown
below has a constant voltage drop of
( 0.6 V ) at all currents and a maximum
power rating of 300 milli watt. What
should be the value of the resistance ( boldsymbol{R} )
if maximum current passes through the diode?
A . ( 4 Omega )
B . ( 2 Omega )
( c .1 Omega )
D. ( 32 Omega )
7
9Material used in fuse wire must have
A. high melting point
B. low melting point
c. high resistance
D. none
7
10Bells are made of metal and not of wood
because:
This question has multiple correct options
A. Metals are elastic than wood
B. The density of the metal is greater than that of wood
C. The sound is not conducted by metals but is radiated
D. Wood dampens vibrations faster
7
11Why is an electromagnet more
advantageous?
A. It produces a strong magnetic field
B. The magnitude of the magnetic field can be easily changed
C. Reversing the current changes the polarity of the magnet
D. All of the above
7
12When the switch of an electric bell is
pushed
A. Flow of the current stops through the electromagnet in the bell
B. Current starts to flow through the electromagnet
c. voltage decreases in the current flowing through the electromagnet
D. None of the above
7
13Which of the following can be used to lift giant industrial machines?
A. electromagnets
B. permanent magnets
c. both A and B
D. none of the above
7
14During a doorbell ringing
A. Current always flows in the circuit
B. Electromagnet is always present
C. Striker is always in contact with metal gong
D. Striker always repeatedly hits metal gong
7
15Which of the following is not a component of electric bell?
A. Gong
B. Ferromagnetic strip
C. Low magnetic field permanent magnet to attract ferromagnetic strip
D. None of the above
7
16The magnetic effect of electric current is used in a/an:
A. electric motor
B. geyser
c. electromagnet
D. electric bulb
7
17In the above circuit diagram, identify
diode(diodes) which is(are) forward
biased.
A. Only ( D_{1} )
B. Only ( D_{2} )
c. Both ( D_{1} ) and ( D_{2} )
D. Neither ( D_{1} ) nor ( D_{2} )
7
18The function of a fuse wire is
independent of :
A. its specific resistance
B. its radius
c. its length
D. current flowing through it
7
19Fuse wire is made up of an alloy of which has high resistance and7
20Fuse is always connected to the wire.
A. live
B. neutral
c. earth
D. green
7
21Which of the following acts as a circuit protecting device?
A. Conductor
B. Inductor
c. switch
D. Fuse
7
22Mark the correct difference between a
permanent magnet and an electromagnet.
A. Permanent magnet does not require any external electric supply to produce the field. But their magnetic field is normally weaker than that of an electromagnet.
B. Hence, permanent magnets are relatively bulky in size compared to electromagnets.
C. The applications of permanent magnet in the field of engineering are quite limited
D. All
7
23The cable of an electric fan becomes so
worn that the live wire makes electrical
contact with the metal case The case is
earthed The plug to the fan contains a 5 A fuse There is a current of 4 A when the
fan works normally What will happen in
this case?
A. The current will run to earth and the fuse will not be affected
B. The metal case will become very hot
c. The metal case will become live and dangerous
D. The fuse will melt and switch off the circuit
7
24While a collector to emitter voltage is constant in a transistor, the collector
current changes by ( 8.2 m A ) when the
emitter current changes by ( 8.3 m A ). The
value of forward current ratio ( boldsymbol{h}_{f e}(text { or } boldsymbol{alpha}) )
is
A .0 .9879
B. 8.30
c. 8.2158
D. 8.0123
7
25How is the working of an electric bell affected, if alternating current be used instead of direct current?7
26In an household electrical circuit:
a) Where is the MCB ( Miniature Circuit
Breaker ) connected?
b) What is the function of ELCB ( Earth
Leakage Circuit Breaker )?
7
27The function of a fuse in independent of7
28To demagnetise a given magnet by electrical method, the ends of the
insulated copper wire wound round the bar magnet should be connected to a
source of
A . ( D C )
в. ( A C )
c. ( D C ) or ( A C )
D. Depends on strength of the bar magnet to be demagnetisedd
7
29State the characteristics required in a
material to be used as an effective fuse
wire
7
30Electromagnets are used in which of the following?
A. Speaker
B. Motor
c. Generator
D. All of the above
7
31The essential requirements of a fuse
wire are
A. High resistance and high melting point
B. High resistance and low melting point
C . Low resistance and low melting point
D. Low resistance and high melting point
7
32is used in making electromagnets.7
33The commonly used safety fuse wire is
made of
A. copper
B. lead
c. nickel
D. an alloy of tin and lead
7
34Name few devices which an
electromagnet is used
7
35Fuse wire is made up of
A. Alloy
B. Mixture
c. Metals
D. Non metals
7
36What is/are the advantage of MCB over
fuses?
This question has multiple correct options
A. Its wire melts unlike fuses wire
B. It automatically turn off to save from excess electricity
c. It takes less time to break the circuit as compare to fuse while overloading
D. None of these
7
37You have been provided with a solenoid
( A B )
(i) What is the polarity at end ( A ? )
(ii) Give one advantage of an
electromagnet over a permanent
magnet.
7
38List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.7
39Working of electric bells is an example
of
A. Mechanical effect of electric current
B. Heating effect of electric current
c. Magnetic effect of electric current
D. None of these
7
40When the switch of an electric bell is
pushed
A. Flow of the current stops through the electromagnet in the bell
B. Current starts to flow through the electromagnet
c. voltage decreases in the current flowing through the electromagnet
D. Circuit is closed in the electric bell
7
41Two fuse wires of the same length are rated 5 A and 20 A.Which of the fuse
wires is thicker and why?
A. 5 A
B. 20 A
c. Both have same thickness
D. Cannot be same
7
42What will happen if the strip in a doorbell loses its flexibility?
A. Striker may break if current is large.
B. After hitting the metal gong, it never returns to original position and only a single sound is produced
c. system of doorbell breaks
D. Both A and B
7
43Choose the correct option
This question has multiple correct options
A. ( mathrm{MCB} ) is much more sensitive to over current than fuse
B. Fuse is much more sensitive to over current than MCB
C. Handling MCB is more electrically safe than fuse
D. Handling fuse is more electrically safe than MCB
7
44Complete the following sentences:
A fuse is a short piece of wire of high and of material of low
A . resistance, melting point
B. meting point, resistance
c. capacitance, melting point.
D. conductance, melting point
7
45Study of relationship between electricity and magnetism is called
A. Current electricity
B. Electric magnetism
c. Magneto electricity
D. Electromagnetism
7
46What will happen if the striker of a doorbell is kept in a magnetic field in a direction perpendicular to motion of striker
A. Striker Hits Harder
B. Striker rebounds harder
c. More current is drawn
D. No effect
7
47In each of the following circuit diagrams, identify which diode(diodes) is(are) forward biased
( A cdot ) Only ( D_{2} )
B. only ( D_{1} )
c. Both ( D_{1} ) and ( D_{2} )
D. Neither ( D_{1} ) nor ( D_{2} )
7
48Fuse blows because
A. There is a high voltage connected across the circuit
B. There is a high current flowing through the circuit
C. There is a high charge that has passed through the circuit
D. The effective resistance of the circuit is too high
7
49In the following circuit, find the diode current when the diode potential is
( 0.5 V . ) Also find the forward resistance of
the diode.
A. ( 0.5 A, 1 Omega )
B ( .1 A, 0.5 Omega )
c. ( 2 A, 1 Omega )
D. ( 5 A, 6 Omega )
7
50Choose the wrong option regarding
miniature circuit breaker (MCB)?
A. MCB contains a metal which melts when the current passing through it exceeds a certain value and hence opens the circuit
B. Quick restoration of an MCB is possible just by switching on the operation when a breakdown occurs due to current overload
C. MCB switchess off the circuit automatically when the current passing through it exceeds a certain value
D. None of the above
7
51A diode is connected in a circuit as
shown in the figure. The correct
statement related to this figure is?
7
52Assertion
In case of electric bell if AC power supply is used then its amplitude of the supply must be sufficiently high.
Reason
Due to AC supply there will be continuous magnetization and demagnetization 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
7
53The material used for making the
armature of electric bell is
A . aluminum
B. soft iron
c. steel
D. bronze
7
54Which of the following is false about
fuse?
This question has multiple correct options
A. A fuse controls the current that flows to the appliance.
B. A fuse increases the resistance in the circuit to
minimize the current flow.
C. A fuse allows high current to flow through the circuit without damaging the appliance.
D. A fuse protects the wiring and the appliance in the circuit from overheating
7
55Assertion
Fuse wire must have high resistance
and low melting point.
Reason
Fuse is used for small current flow 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
7
56Three fuse wires ( A, B ) and ( C ) tinned
copper having identical cross section and length ( 8 mathrm{cm}, 12 mathrm{cm} ) and ( 16 mathrm{cm} ) are
used as fuses. For the same value of
current
A. fuse A will melt first
B. fuse B will melt first
c. fuse C will melt first
D. all fuse will melt for same current
7
57Which is / are the material used for
making the fuse wire. This question has multiple correct options
A. copper
B. Glass
c. Silver
D. silicon
7
58Why are the contact points of an
electric bell made from silver-cadmium
alloy?
7
59Which power supply can be used in electric bell
A. ( A C )
в. ( D C )
c. can’t be predicted
D. Both A and B
7
60Which one of the following statements
is not correct?
A. The two main organs of the human body where the magnetic field produced is quite significant are the heart and the brain.
B. In a house circuit, lamps are used in parallel
C. Switches,fuses and circuit breakers should be placed in the neutral wire
D. A generator with commutator produces direct current
7
61State whether true or false.
When a short-circuit takes place, the fuse wire melts and breaks the electric
circuit.
A. True
B. False
7
62Fuse has ( dots . ) and ( dots . ? )
A. high resistance, high melting point
B. high resistance, low melting point
C . low resistance, high melting point
D. low resistance, low melting point
7
63(i) Name the device used to protect the electric circuits from overloading and short circuits.
(ii) On what effect of electricity does the above device work?
7
64Which of the following statements regarding an electromagnet is NOT true?
A. Insulated wire is wound around it
B. It works only in the presence of electricity
c. It is used in fans and radio
7
65What is an electromagnet? How is it different from a permanent magnet? Describe one application of an electromagnet.7
66Which of the following is the function of MCB in household circuit?
This question has multiple correct options
A. This switches automatically turn off when current exceeds safe limit
B. This switches automatically turn on when current exceeds safe limit
c. saves the electrical appliances from getting damaged due to excess current
D. Saves from shortcircuiting
7
67Name the device that uses an
electromagnet
A. Electric bell
B. Barometer
c. Lactometer
D. All the above
7
68An electromagnets magnetic field can be rapidly manipulated over a wide
range by controlling the amount of electric current supplied to the electromagnet. State whether the above statement is
true or not?
A. True
B. False
7
69Exposed Electric doorbell can be
damaged by
A. Mechanical damage
B. High Electric currents
c. Humidity
D. All of the above
7
70State whether true or false:
An electromagnet can produce very strong magnetic force as compared to permanent magnet
A. True
B. False
7
71In which of the following situations will a fuse possibly melt? This question has multiple correct options
A. The earth wire is broken
B. There is a short circuit in the electrical circuit
c. The fuse is fixed along the neutral wire instead of the live wire
D. The fuse wire is connected to earth wire
7
72An electric iron draws a current of ( 15 mathrm{A} )
from a ( 220 mathrm{V} ) supply. What is the cost of using iron for 30 min everyday for 15 days if the cost of unit (1 unit ( =1 mathrm{k} ) W hr)
is 2 rupees?
A. Rs. 49.5
B. Rs. 60
c. Rs. 40
D. Rs. 10
7
73Two identical p-njunctions may be
connected in series with a battery in three different ways as shown in the
circuit diagrams. In which circuit
diagram will the potential drop across
the p-njunctions be equal?
A. Circuit (1)
B. Circuit (2)
c. circuit (3)
D. Circuit (2) and (3)
7
74How can an electromagnet be made stronger?
A. Add more coils of wire.
B. Add an iron core.
c. Increase the voltage.
D. All of these answers are correct
7
75In the following circuit diagram,
A. the diode is forward biased
B. the diode is reverse biased
C. current due to majority charge carriers flow from ( A ) to ( B )
D. current due to majority charge carriers flows from ( B ) to ( A )
7
76What is the current through an electrical appliance of rating ( 5 mathrm{kW}, 200 ) V and can you use a fuse which is rated
( 8 mathrm{A} ? )
A. 25 A, yes
B. 2.5 A, yes
( c cdot 25 ) A, no
D. 2.5 A, no
7
77A fuse is always connected in the live wire of the circuit. Explain the reason7
78Which of these devices uses a magnet or electromagnet to make it work?
A. An electric bell
B. A compact disc
c. A microchip
D. All of these
7
79Assertion(A): However long a fuse wire may be, the safe current that can be
allowed is the same.
Reason (R) : The safe current that can be allowed to pass through a fuse wire depends on the radius of the wire.
A. Both (A) and (R) are true and (R) is the correct explanation of A
B. Both (A) and (R) are true but (R) is not the correct explanation of
c. (A) is true but (R) is false
D. (A) is false but (R) is true
7
80On over loading of a given circuit a fuse wire will melt.7
81Match the following
1. Horse-shoe
a. Holds the armature in
magnet place
2. Armature
b. Electromagnet
c. Passes electric current to the
3. Spring strip ( quad ) spring strip
4. Adjusting
d. Fixed to the spring strip screw
( mathbf{A} cdot 1-d, 2-a, 3-c, 4-b )
B. ( 1-a, 2-c, 3-b, 4-d )
( mathbf{c} cdot 1-b, 2-d, 3-a, 4-c )
D. ( 1-c, 2-b, 3-d, 4-a )
7
82The main fuse is connected in:
A. live wire.
B. neutral wire.
c. both the live and earth wires.
D. both earth and neutral wire.
7
83In the circuit shown in figure, when the
circuit is completed, the hammer strikes the gong. Which of the following
force is responsible for the movement of
hammer?
A. Gravitational force alone
B. Electrostatic force alone
c. Magnetic force alone
D. Frictional force alone
7
84Which of the following is not true about the advantages of electromagnet over permanent magnet?
A. Small electromagnets are used in electronic lock
B. Scrapyard cranes have powerful electromagnets that lift metal car bodies with ease
c. Magnetic Resonance Imaging machines use very powerful electromagnets to produce highly detailed images of the human body
D. None of the above
7
85What is an electromagnet ? List any two
uses
7
86A fuse wire is always connected to the
A. earth wire
B. neutral wire
C. live wire
D. none of these
7
87A fuse wire with a radius of ( 0.1 m m )
blows up at ( 5 A ). The radius of another
fuse wire made of the same material
which will blow up at ( 40 A ) is
( mathbf{A} cdot 0.8 m m )
B. ( 0.6 m m )
( mathrm{c} .0 .45 mathrm{mm} )
D. ( 0.4 m m )
7
88Armature is pulled towards the spring when it strikes the gong because
A. The electromagnet gets demagnetized
B. The current flow breaks
c. spring effect
D. All of the above
7
89Factors affecting the strength of electromagnet
A. the number of turns in the coil
B. the current flowing in the coil
c. the length if air gap between the poles.
D. all
7
90What is immaterial for an electric fuse?
A . Its length
B. Its radius
C. Its specific resistance
D. Current flowing through it
7
91Electric doorbell
A. Always consume power
B. Consume power only when switch is pressed
C. Do not consume power practically and needs only starting power
D. cant say
7
92Which are the correct for fuse wire?
This question has multiple correct options
A. High resistance
B. low resistance.
C . low melting point.
D. high melting point.
7
93An electromagnet is a
A. Temporary magnet
B. Permanent magnet
C. Both (A) and (B)
D. None of the above
7
94If a piece of soft iron is placed inside the
coil ( n ) number of turns and current is
passed in the coil from a battery, what name is then given to the device so obtained?
A. spectrometer
B. gravitometer
c. barometer
D. electromagnet
7
95Explain the meaning of the statement
current rating of a fuse is ( 5 mathrm{A} ) ‘.
7
96Fuse wire should be placed in the path
of wire
A. Neutral
B. Phase
c. Earth
D. None of these
7
97An ( ldots ) employed in an electric bell.
A. steel
B. electromagnet
c. permanent
D. right angles
7
98A fuse wire is always connected to the
A. earth wire
B. neutral wire
C. live wire
D. none of these
7
99What is the use of flexibility strip in a doorbell?
A. It brings back striker to its original position
B. It supports the motion of the striker
c. It completes the electric circuit flexibly
D. Its a safety precaution
7
100The soft-iron core of an electromagnet loses its magnetism once the current passing through the electromagnetic coil stops because.
A. Domains lose their alignment when the current is stopped
B. Iron cannot hold alignment for longer time even when the current is passing through the coil
c. Magnetic properties of iron are weak
D. Domains inside the iron get aligned in north to south direction
7
101An electromagnet:
A. has its own persistent magnetic field
B. acts as a magnet when an electric current passes through it
C. both ( A ) and ( B )
D. none of the above
7
102Which process is applied on a circuit for the working of an electric bell?
A. Magnetization
B. Make and break
c. Both A and B
D. None of the above
7
103Fuse wire is made of :
A. Platinum
B. Copper
C. Aluminium
D. Alloy in tin and lead
7
104Assertion
In its rest position the clapper is held away from the bell a short distance by
its springy arm.
Reason
The spring constant of spring must be such that clapper should be able to give
reaction to the magnetic force of
attraction upto a certain extent
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
7
105State whether true or false.
Fuses should be connected to the
neutral wire.
A. True
B. False
7
106Fuse wire is a
A. tin-lead alloy
B. copper-lead alloy
C. tin-copper alloy
D. silver-lead alloy
7
107Find out the current in the circuit
shown above. (Assume the diode used
in the circuit is ideal)
A. ( 20 mathrm{mA} )
B. 200 mA
c. ( 0.2 mathrm{A} )
D. ( 40 mathrm{A} )
7
108Electromagnetic are made of soft iron
because soft iron has.
A. High susceptibility and low retentivity
B. Low susceptibility and high retentivity
c. Low susceptibility and low retentivity
D. High susceptibility and high retentivity
7
109When the switch of an electric bell is on
then electric current in it :
A. Flows and stops in succession
B. Flows continuously
c. First flows in one direction and after sometime in other direction
D. Flows in beginning and then stops forever
7
110In an electric bell a flat ( ldots ). spring brings the armature back to its original position.7
111What advantage does an
electromagnet have over a permanent
magnet?
A. An electromagnet can be used for picking up more metals
B. An electromagnet can be switched off.
c. An electromagnet is lighter
D. All of these
7
112Two identical fuses are rated at 10 A. If
they are joined
(A) in parallel, the combination acts as
a fuse of rating 20 A
(B) in parallel, the combination acts as a fuse of rating 5 A
(C) in series, the combination acts as a
fuse of rating 10 A
(D) in series, the combination acts as a
fuse of rating ( 20 mathrm{A} ) Select the correct options
( A cdot A, B )
B. A, C
c. В, D
D. B, C, D
7
113Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain7
114A fuse wire is generally made of
A. tin
B. tin-lead alloy
c. copper
D. either (a) or (b) above
7
115If a fuse is rated as ( 8 mathrm{A} ), and current
more than 8 A passes through it then
A. it would melt
B. circuit gets broken
( c . ) both
D. none
7
116The parameter irrelevant for an electric
fuse wire is
A. its radius.
B. its specific resistance
c. current flowing through it.
D. its length.
7
117What is MCB? Why is MCB preferred to electric fuse?7
118In an electric circuit, a fuse is connected :
A. in the live wire
B. in the neutral wire
c. in the earth wire
D. Any of these
7
119What must happen for an electromagnet to have a magnetic field?
A. It must be heated
B. It must be touching another magnett
c. It must be lined up with earth’s magnetic field
D. It must be connected to an electrical source
7
120What is a fuse ? How does it work?7
121The strength of the magnetic field of an electromagnet :
A. is always greater than that of a permanent magnet
c. can be adjusted
D. none of the above
7
122What is a semi conductor diode or
junction diode?
7
123Fill in the blank-
An electric fuse works on the
effect of current.
A. heating
B. magnetic
c. chemical
D. none of these
7
124State whether true or false:
An electromagnet requires a continuous supply of current to maintain the magnetic field.
A. True
B. False
7
125Electric Fuse wire is working on principle.
A. control of voltage in circuit
B. chemical effect of electric current
C. control of current in circuit
D. heating effect of electric current
7
126Once the applied electric current is removed, the electromagnet:
A. retains its magnetism
B. loses its magnetism
c. gets magnetized in opposite direction
D. none of the above
7
127Fuses used in a household generally have a rating of
( A cdot 500 A )
B. 5A
c. ( 30 A )
D. 220A
7
128State two differences between an
electromagnet and a permanent
magnet.
7
129Name the device which is used to
prevent electrical circuits.
7
130The circuit breaker device which can be
used in place of a fuse is called
A. свD
в. мсв
c. мсо
D. свF
7
131Which one is correct for fuse wire?
A. low resistance and low melting point
B. high resistance and high melting point
C . high resistance and low melting point
D. low resistance and high melting point
7
132The most effective method of
magnetisation is
A. single touch method
B. Double touch method
c. Electrical method
D. All the above
7

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