CBSE Class 12 Physics Electromagnetic Induction MCQs Set C

Question: Which of the following statements is not correct?
a) Whenever the amount of magnetic flux linked with a circuit changes, an emf is induced in 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.
Answer: d

Question: Direction of current induced in a wire moving in a magnetic field is found using
a) Fleming’s left hand rule
b) Fleming’s right hand rule
c) Ampere’s rule
d) Right hand clasp rule
Answer: b

Question: The 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) NAB/2
b) NAB
c) NAB/4
d) zero
Answer: d

Question: A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, the current will
a) increase
b) decrease
c) remain same
d) first increase then decrease
Answer: b

Question: Identify 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 braking force in moving trains.
Answer: a

Question: If number of turns in primary and secondary coils is increased to two times each, the mutual inductance
a) becomes 4 times
b) becomes 2 times
c) becomes 1/4 times
d) remains unchanged
Answer: a

Question: When the rate of change of current is unity, the induced emf is equal to
a) thickness of coil
b) number of turns in coil
c) coefficient of self inductance
d) total flux linked with coil
Answer: c

Question: The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a galvanometer. The maximum deflection of the galvanometer was observed when the magnet was
a) moving towards the solenoid
b) moving into the solenoid
c) at rest inside the solenoid
d) moving out of the solenoid
Answer: d

Question: Faraday’s laws are consequence of the conservation of
a) charge
b) energy
c) magnetic field
d) both energy and magnetic field
Answer: b

Question: Lenz’s law is a consequence of the law of conservation of
a) charge
b) energy
c) induced emf
d) induced current
Answer: b

Question: A metal plate can be heated by
a) passing either a direct or alternating current through the plate.
b) placing in a time varying magnetic field.
c) placing in a space varying magnetic field, but does not vary with time.
d) both (a) and (b) are correct.
Answer: d

Question: The north pole of a bar magnet is rapidly introduced into a solenoid at one end (say A). Which of the following statements correctly depicts the phenomenon taking place?
a) No induced emf is developed.
b) The end A of the solenoid behaves like a south pole.
c) The end A of the solenoid behaves like north pole.
d) The end A of the solenoid acquires positive potential.
Answer: c

Question: Which of the following does not use the application of eddy current?
a) Electric power meters
b) Induction furnace
c) LED lights
d) Magnetic brakes in trains
Answer: c

Question: Two 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
Answer: d

Question: Two inductors of inductance L each are connected in series with opposite magnetic fluxes. The resultant inductance is (Ignore mutual inductance)
a) zero
b) L
c) 2L
d) 3L
Answer: c

Question: There is a uniform magnetic field directed perpendicular and into the plane of the paper. An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper. Then
a) current is induced in the loop in the anticlockwise direction.
b) current is induced in the loop in the clockwise direction.
c) ac is induced in the loop.
d) no current is induced in the loop.
Answer: a

Read the two statement Assertion (A) and Reason (R) carefully to mark the correct option out of the options given below:

(a) Assertion and Reason both are correct statements and Reason is correct explanation for Assertion.
(b) Assertion and Reason both are correct statements but Reason is not correct explanation for Assertion.
(c) Assertion is correct statement but Reason is wrong statement.
(d) Assertion is wrong statement but Reason is correct statement.

Question:
Assertion: When two coil are wound on each other, the mutual induction between the coils is maximum.
Reason: Mutual induced does not depend on the orientation of the coils.
Answer: c

Question:
Assertion: An induced emf is generated when magnet is withdrawn from the solenoid.
Reason: The relative motion between magnet and solenoid induces emf
Answer: a

Question:
Assertion: A copper sheet is placed in a magnetic field. If we pull it out of the field or push it into the field, we experience an opposing force.
Reason: According to Lenz’s law, eddy current produced in sheet opposes the motion of the sheet.
Answer: a

Question:
Assertion: Induced emf depends on number of turns and area of the coil.
Reason: Induced emf increase with increase in number of turns of coil.
Answer: b

Question:
Assertion: Self-inductance is called the inertia of electricity.
Reason: Self-inductance is the phenomenon, according to which an opposing induced emf is produced in a coil as a result of change in current or magnetic flux linked with the coil.
Answer: a

Question:
Assertion: The coil in the resistance boxes are made by doubling the wire.
Reason: Thick wire is required in resistance box.
Answer: c

Question:
Assertion: Acceleration of a magnet falling through a copper ring decreases.
Reason: The induced current produced in a circuit always flow in such direction that it opposes the change or cause that produced it.
Answer: a

Question:
Assertion: An aircraft flies along the meridian, the potential develops at the ends of its wings is same.
Reason: Whenever there is change in the magnetic flux emf induces.
Answer: d

Question:
Assertion: An induced current is developed when the number of magnetic lines of force associated with conductor is changed.
Reason: An induced current develop in a conductor moved in a direction parallel to the magnetic field.
Answer: c

Question:
Assertion: Changing magnetic flux can produce induced emf.
Reason: Faraday established induced emf experimentally.
Answer: b

Assertion (A) & Reason(R)

A – if both Assertion and Reason — are true and Reason — is correct explanation of the Assertion.
B – if both Assertion and Reason — are true but Reason — is not correct explanation of Assertion.
C – if Assertion is true but Reason — is false.
D – if both Assertion and Reason — are false.
E – if Assertion is false but Reason — is true

Question. Assertion– The mutual induction of two coils is doubled, if the self-inductance of the primary or secondary coil is doubled
Reason — Mutual induction is proportional to self-inductance of primary and secondary coils.
Answer: c

Question. Assertion- Making and breaking of current in a coil produce no momentary current in the neighboring coil of another circuit
Reason — Momentary current in the neighboring coil of another circuit is an eddy current.
Answer: d

Question. Assertion- If primary coil is connected by voltmeter and secondary coil by ac source. If large (2020- copper sheet is placed between two coils, induced emf in primary coil is reduced
Reason — Copper sheet between coils has no effect on induced emf in primary coil. 
Answer: a

Question. Assertion- 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.
Answer: c

Question. Assertion- Armature current in DC motor is maximum when the motor has just started
Reason — Armature current is given by I=E-e/R where e is back emf, R is resistance of armature/
Answer: b

Question. Assertion- Eddy current is produced in any metallic conductor when magnetic flux is changed around it
Reason — Electric potential determine the flow of charge.
Answer: b 

Question. Assertion — The quantity L/R possesses dimensions of time
Reason — to reduce the rate of increase of current through a solenoid should increase the time constant L/R.
Answer: b 

Question. Assertion- Faraday laws are consequence of conservation of energy
Reason — In a purely resistive AC circuit, the current lags behind the emf in phase.
Answer: c 

Question. Assertion- Only a change in magnetic flux through a coil maintain a current in the coil if the current is continues
Reason — The presence of large magnetic flux through a coil maintain a current in the coil if the current is continues.
Answer: c 

Question. Assertion – magnetic flux can produce induced emf
Reason — Faraday established induced emf experimentally.
Answer: e