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MCQ On Class 12 Physics Chapter 6 Electromagnetic Induction

(1) When the rate of change oic 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: coefficient of self inductance
(2) 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: LED lights

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(3) 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: The end A of the solenoid behaves like north pole.
(4) 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: Lenz’s law is a consequence of the law of conservation of momentum.
(5) Lenz’s law is a consequence of the law of conservation of
[A] charge
[B] energy
[C] induced emf
[D] induced current
Answer: energy
(6) In the given figure current from A to B in the straight wire is decreasing. The direction of induced current in the loop is A

[A] clockwise
[B] anticlockwise
[C] changing
[D] nothing can be said
Answer: anticlockwise
(7) 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: decrease
(8) 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: both P and Q decreases
(9) The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a short galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. 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: moving out of the solenoid
(10) 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: both (a) and (b) are correct.
(11) 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 A times
[D] remains unchanged 4
Answer: becomes 4 times
(12) 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: 2L
(13) 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 anti-clockwise 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: current is induced in the loop in the anti-clockwise direction.
(14) Faraday’s laws are consequence of the conservation of
[A] charge
[B] energy
[C] magnetic field
[D] both (b) and (c)
Answer: energy
(15) 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: Fleming’s right hand rule
(16) The energy stored in a 50 mH inductor carrying a current of 4 A is:
[A] 0.1 J
[B] 0.4 J
[C] 0.04 J
[D] 0.01 J
Answer: 0.4 J
(17) The magnetic flux linked with a coil is inversely proportional to the?
[A] magnetic field
[B] area of cross section
[C] number of turns
[D] none of these
Answer: magnetic field
(18) The SI unit of magnetic flux is:
[A] T
[B] Tn-2
[C] Wb
[D] Wb m-2
Answer: Wb
(19) coil of L = 8.4 mH and R = 6 Ω is connected to a 12 V battery. The current in the coil is 1.0 A at approx’time of:
[A] 500 s
[B] 20 s
[C] 35 ms
[D] 1 ms
Answer: 1 ms
(20) The role of inductance is equivalent to:
[A] inertia
[B] force
[C] energy
[D] momentum
Answer: inertia

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