# MCQ Questions Chapter 6 Electromagnetic Induction Class 12 Physics

Please refer to MCQ Questions Chapter 6 Electromagnetic Induction Class 12 Physics with answers provided below. These multiple-choice questions have been developed based on the latest NCERT book for class 12 Physics issued for the current academic year. We have provided MCQ Questions for Class 12 Physics for all chapters on our website. Students should learn the objective based questions for Chapter 6 Electromagnetic Induction in Class 12 Physics provided below to get more marks in exams.

## Chapter 6 Electromagnetic Induction MCQ Questions

Please refer to the following Chapter 6 Electromagnetic Induction MCQ Questions Class 12 Physics with solutions for all important topics in the chapter.

MCQ Questions Answers for Chapter 6 Electromagnetic Induction Class 12 Physics

Question. A 800 turn coil of effective area 0.05 m2 is kept perpendicular to a magnetic field 5 × 10–5 T. When the plane of the coil is rotated by 90° around any of its coplanar axis in 0.1 s, the emf induced in the coil will be
(a) 0.02 V
(b) 2 V
(c) 0.2 V
(d) 2 × 10–3 V

A

Question. A coil of resistance 400 W is placed in a magnetic field. If the magnetic flux f (Wb) linked with the coil varies with time t (sec) as f = 50t2 + 4. The current in the coil at t = 2 sec is
(a) 0.5 A
(b) 0.1 A
(c) 2 A
(d) 1 A

A

Question. A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm/s. The induced emf in the loop when the radius is 2 cm is
(a) 4.8p μV
(b) 0.8p μV
(c) 1.6p μV
(d) 3.4p μV

D

Question. A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mm s–1. The induced emf when the radius is 2 cm, is
(a) 2π μV
(b) π μV
(c) π/2 μV
(d) 2 μV

B

Question. A circular disc of radius 0.2 meter is placed in a uniform magnetic field of induction 1/π (Wb/m2) in
such a way that its axis makes an angle of 60° with B¯ The magnetic flux linked with the disc is

(a) 0.08 Wb
(b) 0.01 Wb
(c) 0.02 Wb
(d) 0.06 Wb

C

Question. A rectangular, a square, a circular and an elliptical loop, all in the (x – y) plane, are moving out of a uniform magnetic field with a constant velocity, V¯ = v ^i . The magnetic field is directed along the negative z axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for
(a) the circular and the elliptical loops
(b) only the elliptical loop
(c) any of the four loops
(d) the rectangular, circular and elliptical loops

A

Question. As a result of change in the magnetic flux linked to the closed loop as shown in the figure, an e.m.f. V volt is induced in the loop. The work done (joule) in taking a charge Q coulomb once along the loop is

(a) QV
(b) 2QV
(c) QV/2
(d) zero.

A

Question. A magnetic field of 2 × 10–2 T acts at right angles to a coil of area 100 cm2, with 50 turns. The average e.m.f. induced in the coil is 0.1 V, when it is removed from the field in t sec. The value of t is
(a) 10 s
(b) 0.1 s
(c) 0.01 s
(d) 1 s

B

Question. Faraday’s laws are consequence of conservation of
(a) energy
(b) energy and magnetic field
(c) charge
(d) magnetic field

A

Question. An 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) The current will reverse its direction as the electron goes past the coil
(b) No current induced
(c) abcd

A

Question. A metal ring is held horizontally and bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is
(a) more than g
(b) equal to g
(c) less than g
(d) either(a) or (c)

C

Question. A rectangular coil of 20 turns and area of cross-section 25 sq. cm has a resistance of 100 Ω. If a magnetic field which is perpendicular to the plane of coil changes at a rate of 1000 tesla per second, the current in the coil is
(a) 1 A
(b) 50 A
(c) 0.5 A
(d) 5 A

C

Question. A cycle wheel of radius 0.5 m is rotated with constant angular velocity of 10 rad/s in a region of magnetic field of 0.1 T which is perpendicular to the plane of the wheel. The EMF generated between its centre and the rim is
(a) 0.25 V
(b) 0.125 V
(c) 0.5 V
(d) zero

B

Question. A thin semicircular conducting ring (PQR) of radius r is falling with its plane vertical in a horizontal magnetic field B, as shown in the figure. The potential difference developed across the ring when its speed is v, is

(a) zero
(b) Bvπr2/2 and P is at higher potential
(c) πrBv and R is at higher potential
(d) 2rBv and R is at higher potential

D

Question. The magnetic flux through a circuit of resistance R changes by an amount ΦΔ in a time Δt. Then the total quantity of electric charge Q that passes any point in the circuit during the time Δt is represented by

B

Question. A straight line conductor of length 0.4 m is moved with a speed of 7 m/s perpendicular to a magnetic field of intensity 0.9 Wb/m2. The induced e.m.f. across the conductor is
(a) 5.04 V
(b) 25.2 V
(c) 1.26 V
(d) 2.52 V

D

Question. A conducting square frame of side ‘a’ and a long straight wire carrying current I are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity ‘V’. The emf induced in the frame will be proportional to

B

Question. A long solenoid of diameter 0.1 m has 2 × 104 turns per meter. 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 π2 Ω, the total charge flowing through the coil during this time is
(a) 16 μC
(b) 32 μmC
(c) 16π μC
(d) 32p μC

B

Question. The 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.

C

Question. A current of 2.5 A flows through a coil of inductance 5 H. The magnetic flux linked with the coil is
(a) 0.5 Wb
(b) 12.5 Wb
(c) zero
(d) 2 Wb

B

Question. In which of the following devices, the eddy current effect is not used?
(a) electric heater
(b) induction furnace
(c) magnetic braking in train
(d) electromagnet

A

Question. In a coil of resistance 10 Ω, 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

(a) 8
(b) 2
(c) 6
(d) 4

B

Question. Eddy currents are produced when
(a) a metal is kept in varying magnetic field
(b) a metal is kept in steady magnetic field
(c) a circular coil is placed in a magnetic field
(d) current is passed through a circular coil

A

Question. The current (I) in the inductance is varying with time according to the plot shown in figure. Which one of the following is the correct variation of voltage with time in the coil ?

D

Question. A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is
(a) four times per revolution
(b) six times per revolution
(c) once per revolution
(d) twice per revolution

D

Question. The current i in a coil varies with time as shown in the figure. The variation of induced emf with time would be

A

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) 1.389 H
(d) 13.89 H

D

Question. A long solenoid has 500 turns. When a current of 2 ampere is passed through it, the resulting magnetic flux linked with each turn of the solenoid is 4 × 10–3 Wb. The self-inductance of the solenoid is
(a) 1.0 henry
(b) 4.0 henry
(c) 2.5 henry
(d) 2.0 henry

A

Question. For a coil having L = 2 mH, current flow through it is I = t2e–t then, the time at which emf becomes zero
(a) 2 sec
(b) 1 sec
(c) 4 sec
(d) 3 sec.

A

Question. A uniform magnetic field is restricted within a region of radius r. The magnetic field changes with time at a rate dB¯/dt Loop 1 of radius R > r encloses the region r and loop 2 of radius R is outside the region of magnetic field as shown in the figure. Then the e.m.f. generated is

D

Question. Two coils have a mutual inductance 0.005 H. The current changes in the first coil according to equation I = I0 sinϖt, where I0 = 10 A and w = 100π rad/sec. The maximum value of e.m.f. in the second coil is
(a) π
(b) 5π
(c) 2π
(d) 4π

B

Question. Two coils of self inductance 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) 16 mH
(b) 10 mH
(c) 6 mH
(d) 4 mH

D

Question. If N is the number of turns in a coil, the value of self inductance varies as
(a) N0
(b) N
(c) N2
(d) N–2

C

Question. A 100 millihenry coil carries a current of 1A. Energy stored in its magnetic field is
(a) 0.5 J
(b) 1 J
(c) 0.05 J
(d) 0.1 J

C

Question. The current in self inductance L = 40 mH is to be increased uniformly from 1 amp to 11 amp in 4 milliseconds. The e.m.f. induced in inductor during process is
(a) 100 volt
(b) 0.4 volt
(c) 4.0 volt
(d) 440 volt

A

Question. If the number of turns per unit length of a coil of solenoid is doubled, the self-inductance of the solenoid will
(a) remain unchanged
(b) be halved
(c) be doubled
(d) become four times

D

Question. An inductor may store energy in
(a) its electric field
(b) its coils
(c) its magnetic field
(d) both in electric and magnetic fields

C

Question. In a region of magnetic induction B = 10–2 tesla, a circular coil of radius 30 cm and resistance π2 ohm is rotated about an axis which is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is
(a) 4π2 mA
(b) 30 mA
(c) 6 mA
(d) 200 mA

C

Question. What is the self-inductance of a coil which produces 5 V when the current changes from 3 ampere to 2 ampere in one millisecond?
(a) 5000 henry
(b) 5 milli-henry
(c) 50 henry
(d) 5 henry

B

Assertion-Reason Questions

In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct answer out of the following choices.
(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 A.
(c) A is true but R is false.
(d) A is false and R is also false.

Question. Assertion (A): Faraday established induced emf experimentally.
Reason (R): Magnetic flux can produce an induced emf.

A

Question. Assertion (A): Acceleration of a vertically falling magnet through a horizontal metallic ring is less than g.
Reason (R): Current induced in the ring opposes the fall of magnet.

A

Question. Assertion (A): Only a change of magnetic flux will maintain an induced current in the coil.
Reason (R): The presence of a large magnetic flux will maintain an induced current in the coil.

C

Question. Assertion (A): An emf is induced in a closed loop where magnetic flux is varied. The induced field E is not a conservative field.
Reason (R): The line integral  E.dl around a closed path is non-zero.

C

Question. Assertion (A): Two identical co-axial circular coils carry equal currents circulating in same direction. If coils approach each other, the current in each coil decreases.
Reason (R): When coils approach each other, the magnetic flux linked with each coil increases.
According to Lenz’s law, the induced current in each coil will oppose the increase in magnetic flux, hence, the current in each coil will decrease.

A

Question. Assertion (A): The direction of induced emf is always such as to oppose the changes that causes it.
Reason (R): The direction of induced emf is given by Lenz’s law .

B

Question. Assertion (A): If current changes through a circuit, eddy currents are induced in nearby iron piece.
Reason (R): Due to change of current, the magnetic flux through iron piece changes, so eddy currents are induced in iron piece.

A

Question. Assertion (A): When a rod moves in a transverse magnetic field, an emf is induced in the rod; the end becomes magnetic with end A positive.
Reason (R): A Lorentz force evB acts on free electrons, so electrons move from B to A, thus by making end A positive and end B negative.

D

Question. Assertion (A): If we use a battery across the primary of a step up transformer, then voltage is also obtained across secondary.
Reason (R): Battery gives a time varying current, so there is a change in magnetic flux through the secondary of transformer and hence, emf is induced across secondary.