We have provided Class 12 MCQ Questions with Answers to help students understand the concept very well. Solving the MCQ Questions of Class 12 Physics can be of extreme help as you will be aware of all the concepts. These MCQ Questions of Electromagnetic Induction Class 12 with answers pave for a quick revision of the Chapter thereby helping you to enhance subject knowledge.

Class 12 Physics MCQ Questions of Electromagnetic Induction with Answers with Answers were prepared based on the latest exam pattern. Have a check once the MCQ Questions Physics Class 12 and cross-check your answers during preparation.

Practice MCQ Question for Class 12 Physics chapter-wise 

1. The coupling co-efficient of the perfectly coupled coils is:

(a) Zero
(b) 1
(c) slightly more than 1
(d) infinite

2. The role of inductance is equivalent to:

(a) inertia
(b) force
(c) energy
(d) momentum

3. A choke is used as a resistance in :

(a) dc circuits
(b) ac circuits
(c) both ac and dc circuits
(d) neither (a) nor (b)

4. The SI unit of magnetic flux is:

(a) T
(b) Tn^-2
(c) Wb
(d) Wb m^-2

5. For purely capacitive circuits, power factor is:

(a) 0
(b) -1
(c) 1
(d) infinity

6. The core of a transformer is laminated because:

(a) rusting of core may be prevented
(b) ratio of voltage in primary and secondary may be increased.
(c) energy losses due to eddy current may be minimised
(d) The weight of transformer may be reduced

7. 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

8. Lenz’s law is a consequence of the law of conservation of

(a) charge
(b) mass
(c) energy
(d) momentum

9. When current i passes through an inductor of self inductance L, energy stored in it is 1/2. Li². This is stored in the

(a) current
(b) voltage
(c) magnetic field
(d) electric field

10. 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

11. 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

12.  A moving conductor coil produces an induced e.m.f. This is in accordance with

(a) Lenz’s law
(b) Faraday’s law
(c) Coulomb’s law
(d) Ampere’s law

13. A coil of insulated wire is connected to a battery. If it is taken to galvanometer, its pointer is deflected, because

(a) the induced current is produced
(b) the coil acts like a magnet
(c) the number of turns in the coil of the galvanometer are changed
(d) None of these

14. The laws of electromagnetic induction have been used in the construction of a

(a) galvanometer
(b) voltmeter
(c) electric motor
(d) generator

15. Two identical coaxial circular loops carry a current i each circulating in the same direction. If the loops approach each other, you will observe that the current in

(a) each increases
(b) each decreases
(c) each remains the same
(d) one increases whereas that in the other decreases

16. Magnetic flux is

(a) total charge per unit area
(b) total current through a surface
(c) total number of magnetic field lines passing normally through given area
(d) total e.m.f. in closed circuit

17. A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An e.m.f. is induced in the loop, if 

(a) it is translated
(b) it is rotated about its axis
(c) both (a) and (b)
(d) it is rotated about its diameter

18. Eddy currents do not produce

(a) heat
(b) a loss of energy
(c) spark
(d) damping of motion

19. A coil of insulated wire is connected to a battery. If it is connected to galvanometer, its pointer is deflected, because

(a) induced current is set up
(b) no induced current is set up
(c) the coil behaves as a magnet
(d) the number of turns is changed

20. Direction of current induced in a wire moving in a magnetic field is found using

(a) Fleming’s left found rule
(b) Fleming’s right hand rule
(c) Ampere’s rule
(d) Right hand clasp rule

21. The polarity of induced emf is given by

(a) Ampere's circuital law
(b) Biot-Savart law
(c) Lenz’s law
(d) Fleming's right hand rule

22. The coils in resistance boxes are made from doubled insulated wire to nullify the effect of

(a) heating
(b) magnetism
(c) pressure
(d) self induced e.m.f.

23. 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

24. Which of the following is not the application of eddy currents?

(a) Induction furnace
(b) Dead beat galvanometer
(c) speedometer
(d) X-ray crystallography

25. 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:

1. Answer : (b) 1

Explanation: If the value of k is 1 then the two coils are perfectly coupled or 100% coupling between them.

2. Answer : (a) inertia

Explanation: The role of inductance is equivalent to inertia.

3. Answer : (b) ac circuits

Explanation: A choke coil is used as resistance in AC circuits.

4. Answer : (c) Wb

Explanation: Weber, unit of magnetic flux in the International System of Units (SI), defined as the amount of flux that, linking an electrical circuit of one turn (one loop of wire), produces in it an electromotive force of one volt as the flux is reduced to zero at a uniform rate in one second.

5. Answer : (a) 0

Explanation: Power in circuit (P)=V _rmsI _rms cosϕ = V_rms I_rmscos90^o = 0

6. Answer : (c) energy losses due to eddy current may be minimised

Explanation: The core of a transformer is laminated to minimise the energy losses due to eddy currents.

7. Answer : (a) electromagnetic induction

Explanation: Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called electromagnetic induction.

8. Answer : (c) energy

Explanation: Lenz's law is a manifestation of the conservation of energy. The induced emf produces a current that opposes the change in flux, because a change in flux means a change in energy. Lenz's law is a consequence.

9. Answer : (c) magnetic field

Explanation: A magnetic field is induced in the space between the inductor.  And this magnetic field corresponds to energy.

10. Answer : (a) A metal is kept in varying magnetic field

Explanation: They arise when a conductor moves through a magnetic field, or when the magnetic field surrounding a stationary conductor is varying. Summarising, we can say that anything which results in the conductor experiencing a change in the intensity or direction of a magnetic field produces eddy currents.

11. Answer : (a) electric field is produced by time varying magnetic flux

Explanation: According to Faraday's Law of electromagnetic induction, if magnetic flux through a coil changes, it leads to an induced emf across the coil. Hence, electric field is produced by time-varying magnetic fields.

12. Answer : (b) Faraday’s law

Explanation: Faraday's Law states that when the magnetic flux linking a circuit changes, an electromotive force is induced in the circuit proportional to the rate of change of the flux linkage. 
This results in a moving conductor coil producing EMF.

13. Answer : (a) the induced current is produced

Explanation: When electric current is passed through the coil inside the galvanometer, induction of magnetic field takes place and thus the coil acts like a magnet which experiences torque due to permanent magnet inside galvanometer and thus the pointer is deflected.

14. Answer : (d) generator

Explanation: The law of electromagnetic induction have been used in the construction of. In a generator, emf is induced according to Lenz's rule.

15. Answer : (b) each decreases

Explanation: As the two identical coaxial circular loops carry a current i each circulating in the same direction, their flux add each other. When the two are brought closer, the total fluc linkage increase. By Lenz's a law a current will be induced in both the loops such that it opposes this change in flux. As the flux increases, the current in each loop will decreases so as to decrease the increasing flux.

16. Answer : (c) total number of magnetic field lines passing normally through given area

Explanation: Magnetic flux is a measurement of the total magnetic field which passes through a given area.The angle at which the field line intersects the area is also important. A field line passing through at a glancing angle will only contribute a small component of the field to the magnetic flux.

17. Answer : (d) it is rotated about its diameter

Explanation: An emf is induced only when magnetic flux linked with the loop changes. This is possible when the loop is rotated about a diameter.

18. Answer : (c) spark

Explanation: Eddy current circulate within the conductor.

19. Answer : (a) induced current is set up

Explanation: The angle through which the coil is deflected due to the effect of the magnetic torque is proportional to the magnitude of current in the coil.Therefore, when a coil of insulated wire which is connected to a battery, is taken to a galvanometer. Its pointer would deflect because of the production of induced current.

20. Answer : (b) Fleming’s right hand rule

Explanation: Fleming's right hand rule is used to find direction of induced current in a wire moving in a magnetic field.

21. Answer : (c) Lenz’s law

Explanation: The polarity of the induced emf or the current in any circuit is such as to oppose the cause that produces it. This is also known as Lenz's law.

22. Answer : (d) self induced e.m.f.

Explanation: The coils in resistance boxes are made from doubled insulated wire to nullify the effect of self induced e.m.f.

23. Answer : (c) 13.89 H

Explanation: PE = \(\frac{1}{2}LI^2\)

\(25\times10^{-3}=\frac{1}{2}(60\times10^{-3})^2\)

L = 13.89 H

24. Answer : (d) X-ray crystallography

Explanation: Induction furnace, galvanometer damping and speedometer of automobile are the application of eddy currents. Crystallography is done by diffraction.

25. Answer : (d) 37.5 V

Explanation: 

\(e=M\frac{dI}{dt}\)

\(=\frac{0.75\times0.5}{0.01}\)

= 37.5 V

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