CBSE Class 12 Physics Electromagnetic Induction MCQs Set A

Question: Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called
(a) electromagnetic induction
(b) lenz’s law
(c) hysteresis loss
(d) kirchhoff’s laws
Answer: A

Question: According to Faraday’s law of electromagnetic induction
(a) electric field is produced by time varying magnetic flux.
(b) magnetic field is produced by time varying electric flux.
(c) magnetic field is associated with a moving charge.
(d) None of these
Answer: A

Question: Lenz’s law is a consequence of the law of conservation of
(a) charge
(b) mass
(c) energy
(d) momentum
Answer: C

Question: A 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) llarger or smaller depending upon the radius of the coil

Answer: A

Question: A current carrying infinitely long wire is kept along the diameter of a circular wire loop, without touching it, the correct statement(s) is(are)
I. The emf induced in the loop is zero if the current is constant.
II. The emf induced in the loop is finite if the current is constant.
III. The emf induced in the loop is zero if the current decreases at a steady rate
(a) I only
(b) II only
(c) I and II
(d) I, II and III
Answer: A

Question: An 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
Answer: C

Question: When current i passes through an inductor of self inductance L, energy stored in it is 1/2. L i². This is stored in the
(a) current
(b) voltage
(c) magnetic field
(d) electric field
Answer: C

Question: A coil is wound on a frame of rectangular cross-section. If all the linear dimensions of the frame are increased by a factor 2 and the number of turns per unit length of the coil remains the same, self-inductance of the coil increases by a factor of
(a) 4
(b) 8
(c) 12
(d) 16
Answer: B

Question: The self inductance associated with a coil is independent of
(a) current
(b) time
(c) induced voltage
(d) resistance of coil
Answer: D

Question: The plane in which eddy currents are produced in a conductor is inclined to the plane of the magnetic field at an angle equal to

(a) 45°
(b) 0°
(c) 180°
(d) 90°
Answer: D

Question: Eddy currents are produced when
(a) A metal is kept in varying magnetic field
(b) A metal is kept in the steady magnetic field
(c) A circular coil is placed in a magnetic field
(d) Through a circular coil, current is passed
Answer: A 

Question: When the plane of the armature of a 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 maximum values.
Answer: B

Question: When the current in a coil changes from 2 amp. to 4 amp. in 0.05 sec., an e.m.f. of 8 volt is induced in the coil. The coefficient of self inductance of the coil is
(a) 0.1 henry
(b) 0.2 henry
(c) 0.4 henr
(d) 0.8 henry
Answer: B

Question: Two coils of self inductances 2 mH and 8 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) 6 mH
(b) 4 mH
(c) 16 mH
(d) 10 mH
Answer: B

Question: The mutual inductance of a pair of coils is 0.75 H. If current in the primary coil changes from 0.5 A to zero in 0.01 s, find average induced e.m.f. in secondary coil
(a) 25.5 V
(b) 12.5 V
(c) 22.5 V
(d) 37.5 V
Answer: D

Question: A wire of length 50 cm moves with a velocity of 300 m/min, perpendicular to a magnetic field. If the e.m.f. induced in the wire is 2 V, the magnitude of the field in tesla is
(a) 2
(b) 5
(c) 0.8
(d) 2.5
Answer: C

Question: The coefficient of self inductance of a solenoid is 0.18 mH. If a core of soft iron of relative permeability 900 is inserted, then the coefficient of self inductance will become nearly
(a) 5.4 mH
(b) 162 mH
(c) 0.006 mH
(d) 0.0002 mH
Answer: B

Question: Two solenoids of same cross-sectional area have their lengths and number of turns in ratio of 1 : 2 both. The ratio of self-inductance of two solenoids is
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) 1 : 4
Answer: B

Question: A generator has an e.m.f. of 440 Volt and internal resistance of 4000 hm. Its terminals are connected to a load of 4000 ohm. The voltage across the load is
(a) 220 volt
(b) 440 volt
(c) 200 volt
(d) 400 volt
Answer: B

Question: The magnetic potential energy stored in a certain inductor is 25 mJ, when the current in the inductor is 60 mA. This inductor is of inductance
(a) 0.138 H
(b) 138.88 H
(c) 13.89 H
(d) None of these
Answer: C

Question: The 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 km/hr along the track, given that the vertical component of earth’s magnetic field is 0.2 × 10^–4 wb/m² and rails are separated by 1 metre
(a) 10^–2 volt
(b) 10 mV
(c) 1 volt
(d) 1 mV
Answer: D