# MCQ Questions for Class 12 Physics Chapter 6 Electromagnetic Induction with Answers

Do you need help learning for your NCERT Class 12 Physics exam? Students may want to download NCERT MCQ Questions for Class 12 Physics Chapter 6 Electromagnetic Induction with Answers Pdf free download. These Electromagnetic Induction Class 12 MCQs Questions with Answers can help understand the concepts score better in your Class 12 Physics Exam, so make sure you practice these! Check out chapter-wise MCQ Questions for Class 12 Physics with Answers.

## Electromagnetic Induction Class 12 MCQs Questions with Answers

Solve these Electromagnetic Induction Multiple Choice Questions of Class 12 Physics Chapter 6 MCQ, so as not to miss out on any concept from being clear about what they mean!

Question 1.
A cylindrical bar magnet is rotated about its axis (figure). A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then

(a) a direct current flows in the ammeter A.
(b) no current flows through the ammeter A.
(c) an alternating sinusoidal current flows through the ammeter A with a time period T = 2π/ω.
(d) a time varying non-sinusoidal current flows through the ammeter A.

Answer: (a) a direct current flows in the ammeter A.

Question 2.
There are two coils A and B as shown in figure. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counterclockwise. B is kept stationary when A moves. We can infer that

(a) there is a constant current in the clockwise direction in A.
(b) there is a varying current in A.
(c) there is no current in A.
(d) there is a constant current in the counterclockwise direction in A.

Answer: (d) there is a constant current in the counterclockwise direction in A.

Question 3.
The self-inductance L of a solenoid of length l and area of cross-section A, with a fixed number of turns N increases as
(a) l and A increase.
(b) l decreases and A increases.
(c) l increases and A decreases.
(d) both l and A decrease.

Answer: (b) l decreases and A increases.

Question 4.
A metal plate is getting heated. Which one of the following is not the possible cause?
(a) a direct current is passing through the plate.
(b) it is placed in a time-varying magnetic field.
(c) it is placed in a space-varying magnetic field, but does not vary with time.
(d) a current (either direct or alternating) is passing through the plate.

Answer: (c) it is placed in a space-varying magnetic field, but does not vary with time.

Question 5.
Which of the following will not induce an emf in a coil in the absence of an external voltage source?
(a) the coil being in a time-varying magnetic field.
(b) the coil moving in a time-varying magnetic field.
(c) the coil moving in a constant magnetic field.
(d) the coil is stationary in external spatially varying magnetic field, which does not change with time.

Answer: (d) the coil is stationary in external spatially varying magnetic field, which does not change with time.

Question 6.
A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. This can be because
(a) the magnetic field is constant.
(b) the magnetic field is in the same plane as the circular coil and it may or may not vary.
(c) the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is constant.
(d) there is a constant magnetic field in the perpendicular (to the plane of the coil) direction.

Answer: (b) the magnetic field is in the same plane as the circular coil and it may or may not vary.

Question 7.
The mutual inductance M12 of coil 1 with respect to coil
(a) decreases when they are brought nearer.
(b) depends on the current passing through the coils.
(c) increases when one of them is rotated about an axis.
(d) is the same as M21 of coil 2 with respect to coil 1.

Answer: (d) is the same as M21 of coil 2 with respect to coil 1.

Question 8.
Consider a metal ring kept on a horizontal plane. A bar magnet is held above the ring with its length along the central axis of the ring. If the magnet is now dropped freely, the acceleration of the falling magnet is (g is acceleration due to gravity)

(a) More than g
(b) Equal to g
(c) Less than g
(d) Depends on mass of magnet

Question 9.
A wheel with ten metallic spokes each 0.50 m long is rotated with a speed of 120 rpm in a place normal to the earth’s magnetic field at the place. If the magnitude of the field is 0.04 G, the induced emf between the axle and the rim of the wheel is equal to
(a) 1.256 × 10-3 V
(b) 6.28 × 10-3 V
(c) 1.256 × 10-4 V
(d) 6.28 × 10-6 V

Answer: (d) 6.28 × 10-6 V

Question 10.
The coefficient of self-inductance of a solenoid is 0.18 mH. If a rod 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

II. Fill in the blanks

Question 1.
………………… the magnetic flux can produce an electric current.

Question 2.
Magnetic flux through an area is given by ……………

Answer: Φ = BA cos θ

Question 3.
……………… is the SI unit of magnetic flux.

Question 4.
The magnitude of the induced emf in a circuit is equal to the time rate of change of ……………. through the circuit.

Question 5.
The statement “The polarity of induced emf is such that it tends to produce a current which opposes the change in magnetic flux that produced it” is called ………………. law.

Question 6.
The emf induced in a rod of length / moving with velocity v in a uniform magnetic field B is …………….

Question 7.
Eddy currents are of ……………… nature.

Question 8.
The induced ……………… does not depend upon the time-interval.

Question 9.
The SI unit of mutual inductance is ……………….

Question 10.
Two coils have mutual inductance of 1.5 henry. If the current in the primary circuit is raised by 5 A in one millisecond after closing the circuit, then the induced emf in secondary coil is ……………… volt.

Question 11.
Two concentric circular coils one of small radius a1 and the other of large radius a2 such that a1 << a2, are placed co-axially with centres coinciding. The mutual inductance of the arrangement is ………………

Answer: $$\frac { µ_0l_2a_1^2 }{2a_2}$$

Question 12.
Self-inductance of a long solenoid (A, N, l) with core material of magnetic relative permeability µr is (where A = area of each turn, N = number of turns, L = length of solenoid)

Question 13.
A closed loop moves normal to the constant electric field between the plates of a large capacitor, then no ……………….. is induced in the loop.

Question 14.
According to the reciprocity theorem, the mutual inductance of one coil with respect to the other is ……………..

Answer: M = µ0n1n2πr$$_1^2$$ l

Question 15.
Fleming’s right hand rule gives the direction of ………………. current.

Question 16.
Metal detector is based on the concept of …………….. currents.