Physics MCQs for Class 12 with Answers Chapter 6 Electromagnetic Induction

Electromagnetic Induction MCQ Chapter 6

Below are some of the very important NCERT Electromagnetic Induction MCQ Class 12 Physics Chapter 6 with answers. These Electromagnetic Induction MCQ have been prepared by expert teachers and subject experts based on the latest syllabus and pattern of CBSE Term 1 examination.

We have given these Electromagnetic Induction MCQ Class 12 Physics questions with answers to help students understand the concept.

MCQ Questions for Class 12 Physics are very important for the latest CBSE Term 1 and Term 2 pattern. These MCQs are very important for students who want to score high in CBSE Board, NEET and JEE exam.

MCQ 1- 44

1 . A moving conductor coil is a magnetic field produces an induced EMF this is in accordance with

1. Lenz’s law
2. Coulomb’s law
3. Faraday’s law
4. Ampere’s law

2. An induced EMF is produced when a magnet is plunged into a coil. The strength of the induced EMF is independent of

1. number of turns of coil
2. speed with which the magnet is moved
3. the strength of magnet
4. the resistivity of the wire of the coil

3. The magnetic flux through a coil is inversely proportional to

1. magnetic field
2. number of turns
3. area
4. none of these

4. Faraday’s law are consequences of conservation of

1. energy & magnetic field
2. energy
3. magnetic field
4. charge

5. Lenz’s law give

1. the direction of the induced current
2. the magnitude of the induced EMF
3. the magnitude of the induced current
4. Both the magnitude and direction of the induced current

6. Which of the following phenomena makes use of electromagnetic induction?

1. magnetising an iron piece with a bar magnet
2. generation of hydroelectricity
3. magnetizing a soft iron piece by placing inside a current carrying solenoid
4. charging a storage battery

7. The magnetic flux (ф) linked with a coil due to its own magnetic field is related to the number of turns of coil as

1. Ф ∝ N²
2. Ф ∝ N^-1
3. Ф ∝ N
4. Ф ∝ N^-2

8. In electromagnetic induction, the induced charge is independent of

1. resistance of the coil
2. change of flux
3. time
4. none of these

9. To induce an EMF in a coil, the linking magnetic flux

1. must remain constant
2. can either increase or decrease
3. must increase
4. must decrease

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

1. Q = ΔΦ / R
2. Q = RΔΦ / Δt
3. Q = ΔΦ / RΔt
4. Q = ΔΦ / Δt

11. A coil has 200 turns and area of 70 cm² . The magnetic field perpendicular to the plane of the coil is 0.3 Wb/m² and takes 0.1 s to rotate through 180°. The value of the induced EMF will be

1. 84 V
2. 42 V
3. 8.4 V
4. 4.2 V

12. The expression for the induced EMF contains and negative sign. What is the significance of the negative sign?

1. The induced EMF is opposite to the direction of the flux
2. The induced EMF is produced only when the magnetic flux decreases
3. The induced EMF opposes the changes in the magnetic flux
4. None of the above

13. Lenz’s and Faraday’s law is expressed by the following formula

1. e = -NdΦ/dt
2. e = NdΦ/dt
3. e = -ΦdN/dt
4. e = -d(Φ/N)/dt

14. A rectangular coil of 100 turns and size 0.1 X 0.05 m is placed perpendicular to a magnetic field of 0.1 T. If the field drops to zero point 0.05T in 0.05 s, the magnitude of the EMF induced in the coil is

1. 0.5
2. 3
3. 2
4. 6

15. An electron moves along the line AB, which lies in the same plane as a circular loop of conducting wire as shown in the diagram. What will be the direction of current induced, if any, in the loop?

1. The current will change direction as the electron passes by
2. The current will be anticlockwise
3. The current will be clockwise
4. No current will be induced

16. Eddy Currents may be reduced by using

1. thick piece of Cobalt
2. thick piece of Nickel
3. laminated core of Steel
4. laminated core of soft iron

17. When current changes from 13A to 7A in 0.5s through a coil the EMF induced is 3 x 10^-4. The coefficient of self induction is

1. 25 x 10^-6 H
2. 25 x 10^-5 H
3. 25 x 10^-4 H
4. 25 x 10^-3 H

18. Magnetic flux of 10μWb is linked with a coil, when a current of 2mA flows through it. What is the self inductance of the coil?

1. 20mH
2. 10mH
3. 15mH
4. 5 mH

19. For two coils with number of turns 500 and 200 each of length 1 m and cross sectional area 4 x 10^-4 m², the mutual inductance is

1. 0.5 μH
2. 0.5 H
3. 5 μH
4. 0.05 mH

20. When current I passes through an inductor of inductance L, energy stored in it is 1/2LI². This is stored in the

1. electric field
2. magnetic field
3. voltage
4. current

21. A small coil of N₁ turns, l₁ length is tightly wound over the centre of long solenoid of length l₂, area of cross section A and number of turns N₂. If a current I flows in the small coil, then the flux through the long solenoid is

1. Zero
2. μoN₁N₂AI/l₁
3. μoN₁₂AI/l₁
4. Infinite

22. Which of the following is not a factor to determine the mutual inductance of the two coils

1. current through each coil
2. the number of terms of each coil
3. separation between the coils
4. the shape of each coil

23. Mutual inductance of two coils can be increased by

1. winding the coils on wooden coil
2. decreasing the number of turns in the coil
3. increasing the number of turns in the coil
4. none of these

24. The mutual inductance between two coils depend upon

1. medium between the coils
2. separation between coils
3. neither 1 nor 2
4. both 1 and 2

25. Self inductance ___________ when the number of turns of a coil is doubled

1. is halved
2. is doubled
3. becomes 4 times
4. becomes one quarter

26. Self induction of a solenoid is

1. inversely proportional to area of cross section
2. directly proportional to area of cross section
3. directly proportional to its length
4. directly proportional to current flowing through the coil

27. Two solenoids of same cross sectional area have the length and number of turns in ratio 1:2 both. The ratio of self inductance of two solenoids is

1. 1:2
2. 2:1
3. 1:4
4. 1:1

28. For perfect coupling of two coils of inductance L₁ and L₂ their mutual inductance M should be given by

1. M = √ (L₁L₂)
2. M = L₁ / L₂
3. M = (L₁L₂)^½
4. M = L₁L₂

29. In an inductor of inductance L=100mH, a current of I=10A is flowing. The energy stored in the inductor is

1. 1000 J
2. 100 J
3. 10 J
4. 5 J

30. What will be the self inductance of a coil of 100 turns if a current of 5A produces a magnetic flux of 5 x 10^-5 Wb?

1. 1 μH
2. 10μH
3. 1mH
4. 10mH

31. If the current 30A flowing in the primary coil is made zero in 0.1 s, the EMF induced in the secondary coil is 1.5V. The mutual inductance between the coil is

1. 0.1 H
2. 0.2 H
3. 0.005 H
4. 1.05 H

32. The physical quantity which is measured in the unit of WbA^-1 is

1. magnetic flux
2. self inductance
3. mutual inductance
4. both B and C

33. The coefficient of mutual inductance of two coils is 6mH. If the current flowing in one is 2A, then the induced EMF in the second coil will be

1. Zero
2. 2mV
3. 3mV
4. 3V

34. An EMF of 12V is induced in a given coil when the current in it changes at a rate of 48A/min. The inductance of the coil is

1. 9.6 H
2. 15 H
3. 0.25 H
4. 1.5 H

35. The mutual inductance of a pair of coil is 0.75 H. If current in the primary coil changes from 0.50A to zero in 0.01s, find average induced EMF is in secondary coil

1. 22.5 V
2. 12.5 V
3. 25.5 V
4. 37.5 V

36. In an inductor, having a self inductance of 10 H, the current changes from 10A to 5A in 0.2s. The induced EMF in inductor is

1. 2.5 V
2. 10 V
3. 25 V
4. 250 V

37. Energy stored in a coil of self inductance 40mH carrying a steady current of 2A is

1. 8J
2. 0.08J
3. 0.8J
4. 80J

38. The mutual inductance of an induction coil is 5H. In the primary coil, the current reduces from 5A to zero in 10^-3s. What is the induced EMF in the secondary coil?

1. Zero
2. 2500 V
3. 2510 V
4. 2500 V

39. An air core solenoid has 1000 turns and is 1 m long. Its cross-sectional area is 10 cm². Its self inductance is

1. 0.1256 mH
2. 1.256 mH
3. 12.56 mH
4. 125.6 mH

40. A square of side L in lies in the x-y plane in a region, where the magnetic field is given by, B = Bo (2i + 3j + 4k) T, where Bo is a constant. The magnitude of flux passing through the square is

1. 2B_oL²Wb
2. 3B_oL²Wb
3. 4B_oL²Wb
4. √29B_oL²L2Wb

41. A loop, made of straight edges has six corners at A(0,0,0), B(L,0,0), C(L,L,0), D(0,L,0), E(0,L,L) and F(0,0,L). A magnetic field B = Bo(i+k) T is present in the region. The flux passes through the loop in the region. The flux passing through the loop ABCDEFA is

1. BoL²Wb
2. 2BoL²Wb
3. √2BoL²Wb
4. 4BoL²Wb

42. There are two coils A and B as shown in the 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 conclude that

1. there is a constant current in the clockwise direction in A
2. there is a very current in A
3. there is no current in a there is A
4. constant current in the counterclockwise direction in A

43. 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

1. l and A increases
2. l decreases and A increases
3. l increases and A decreases
4. both l and A decrease

44. A circular loop of radius r, carrying a current I lies in the y-z plane with its centre at the origin. The net magnetic flux through the loop is

1. directly proportional to r
2. zero
3. inversely proportional to r
4. directly proportional to I

Assertion-Reasoning Based MCQ

Code

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Assertion is false but reason is true.

1 . Assertion Faraday’s law are consequence of conservation of energy

Reason In a pure resistive AC circuit, the current lags behind the EMF in phase

2. Assertion Lenz’s law is based on the principle of conservation of energy

Reason Induced EMF always opposes the change in magnetic flux responsible for its production

3. Assertion Two identical loops one of copper and other of aluminium and rotated with the same speed in the same magnetic field. The EMF induced in both the loop will be same.

Reason The magnitude of induced EMF is directly proportional to the rate of change of magnetic flux linked with the circuit

4. Assertion An induced current will be developed in a conductor, if it is moved in a direction parallel to the magnetic field.

Reason Whenever there is relative motion between loop and magnet and induced current is produced in the loop.

5. Assertion Eddy Currents are produced in a metallic conductor when magnetic flux is changed around it

Reason Electric potential determines the flow of charge

6. Assertion An artificial satellite with a metal surface is moving above the earth in a circular orbit. A current will be induced in the satellite if the plane of the orbit is inclined to the plane of the equator.

Reason The current will be induced only when the speed of satellite is more than 8 km/sec

7. Assertion An induced EMF is generated when magnet is withdrawn from the solenoid

Reason The relative motion between magnet and solenoid induces EMF

8. Assertion Only a change in magnetic flux will maintain and induced current in the coil

Reason The presence of large magnetic flux through a coil maintains the current in the coil electric circuit is continuous

9. Assertion mutual inductance of a pair of coil depends on the separation as well as the relative orientation

Reason mutual inductance depends upon the length of the coil only

10. Assertion in the phenomenon of mutual inductance self induction of each of the coil possessed

Reason self induction rises due to change in current in the coil itself in mutual induction current changes in both the individual coil

11. Assertion the self inductance of a long solenoid is proportional to the area of cross section and length of the solenoid

Reason self inductance of a solenoid is independent of the number of turns per unit length

12. Assertion when two coils are wound on each other the mutual inductance between the coil is maximum

Reason mutual inductance does not depend on the orientation of the coils

13. Assertion inductance coil are made of copper

Reason induced current is more in wire having less resistance

Case-Study Based MCQ

1 . Lenz’s law is the mostly used to find the direction current induced in a circuit. According to this law, the polarity of EMF induced in the circuit is such that it opposes or check the variation in magnetic flux responsible for it.

If we move north pole of a bar magnet towards coil, then magnetic flux linked with the coil changes (i.e. increases). Due to this current is induced in the coil in anticlockwise direction. The magnetic moment related with induced current has not polarity towards the north pole. If we move away the bar magnet the magnetic moment has south polarity.

Lenz’s law was the law of conservation of energy.

(i) Lenz’s law is used to find the direction of

(a) electric field

(b) force

(c) induced current

(d) electrostatic force

(ii) Lenz’s law follows the law of

(a) conservation of force

(b) conservation of mass

(c) conservation of momentum

(d) conservation of energy

(iii) What will be the polarity of magnetic moment if we move the north of magnet towards coil?

(a) North

(b) South

(c) Both (a) and (b)

(d) None of these

(iv) If we move away the bar magnet from coil then what will be the direction of induced current in coil.

(a) clockwise

(b) anticlockwise

(c) both (a) and (b)

(d) none of these

(v) As the move the north pole of magnet towards coil, the magnetic flux linked with the coil

(a) increases

(b) decreases

(c) remains same

(d) none of these

2. From the experimental observations for after arrived at a conclusion that an EMF is induced in a coil when magnetic flux through the coil changes with time. The change in magnetic flux induces EMF in coils C₁. It was this induced EMF which cost electric current to flow in coil C₁ and through the galvanometer.

When the tapping key K is pressed, the current enquiry C₂ (and the result in magnetic field) rises from zero to a maximum value in a short time. Consequently, the magnetic flux through the neighboring coil C₁ also increases. It is the change in magnetic flux through a point C₁ that produces an induced EMF in a coil C₁.

The SI unit of magnetic flux is weber. When the key is held pressed current in coil C₂ is constant. Therefore, there is no change in the magnetic flux through coil C₁ and the current in coil C₁ drops to zero. When the key is released, the current in C₂ and the resulting magnetic field decreases from the maximum value to zero in a short time.

This results in a decrease in magnetic flux through coil C₁ and hence again induces an electric current in coil C₁. The common point in all his observation is that the time rate of change in magnetic flux through a circuit induces EMF in it.

Faraday stated experimental observation in form of law called Faraday’s law of electromagnetic induction which states that ‘the magnitude of induced EMF in a circuit is equal to time rate of change of magnetic flux through the circuit.

(i) What is the full form of EMS?

(a) electron movement force

(b) electromotive force

(c) electron monitoring force

(d) electromagnetic field

(ii) Which of the following scientist arrived at a conclusion that an EMF is induced in a coil when magnetic flux through the coil changes with time

(a) Michael Faraday

(b) Joseph Henry

(c) Both Faraday and Henry

(d) Blaise Pascal

(iii) What is the SI unit of magnetic flux?

(a) Pascal

(b) Coulomb

(c) Weber

(d) Tesla

(iv)Who among the following scientist gave the statement, ‘the magnitude of the induced EMF in a circuit is equal to the time rate of change of magnetic flux through the circuit’?

(a) John Dalton

(b) Joseph Henry

(c) Blaise Pascal

(d) Michael Faraday

(v) A rod of length 0.4 m moves in a direction perpendicular to a magnetic field of magnitude 1.2 T. The EMF induced in the moving rod is found to be 2.4 V. What is the speed of the rod?

(a) 0.48 m/s

(b) 2.88 m/s

(c) 7.2 m/s

(d) 5.0 m/s

3. So far we have studied about the electric currents induced in well defined paths in conductor like circular loops. Even when bulk pieces of conductors are subjected to changing magnetic flux, induced currents are produced in the. However, their flow patterns resemble swirling eddies in water.

This effect was discovered by physicist Foucault (1819-1868) and these currents are called eddy currents. A copper plate is allowed to swing like a simple pendulum between the pole pieces of a strong magnet. It is found that the motion is damped and in a little while, the plate comes to a halt in the magnetic field.

We can explain this phenomenon on the basis of electromagnetic induction. Magnetic flux associated with the plate keeps on changing as the plate moves in and out of the region between magnetic poles. The flux change induces eddy currents in the plate. Directions of eddy currents are opposite when the plate swings into the region between the poles and when it swings out of the region.

(i) In which year Faucault was born?

(a) 1819

(b) 1825

(c) 1838

(d) 1868

(ii) Even when bulk pieces of conductors are subjected to changing magnetic flux, induced currents are produced in them. This effect was discovered by which of the following scientist?

(a) John Dalton

(b) Jean Bernard Leon Faucault

(c) Heinrich Friedlich Lenz

(d) Michael Faraday

(iii) What is called magnetic flux?

(a) Magnetic flux is a vector field that describes the magnetic influence on moving electric charges, electric currents and magnetic materials.

(b) Magnetic flux is the production of an electromotive force across an electric conductor in a changing magnetic fields.

(c) Magnetic flux is a measurement of the total magnetic field which passes through a given area.

(d) Magnetic flux is a rectangular piece of an object that shows permanent magnetic properties and are made from the ferromagnetic substance.

(iv) Eddy current can be defined as

(a) Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday’s law of induction.

(b) Eddy currents are the magnitude of the induced EMF in a circuit is equal to the time rate of change of magnetic flux through that circuit

(c) Eddy currents are the polarity of induced EMF such that it tends to produce a current which opposes the change in magnetic flux that produces it.

(d) None of these

(v) If a current of 2A gives rise to a magnetic flux of 5 x 10^-5 Wb through a coil having 100 turns, then the magnetic energy stored in the medium surrounding the coil is

(a) 5 J

(b) 50 J

(c) 5 x 10^-3 J

(4) 0.5 J