R4RIN – MCQs, Mock Tests | NCERT Class 12 MCQ Questions for Class 12 Physics Chapter 6 Electromagnetic Induction

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

1. Zero
2. 1
3. slightly more than 1
4. infinite

✅ Correct Answer: 2

The magnetic field is parallel to a surface, then the magnetic flux through the surface is :

1. zero
2. small but not zero
3. infinite
4. large but not infinite

✅ Correct Answer: 2

An e– and a p– are moving parallel to each other in a magnetic field. The magnetic force acting on the p+ is:

1. 1840 times that on e–
2. less than that of e–
3. same as that of e–
4. slightly more than that of e–

✅ Correct Answer: 3

A transformer is used to light 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A. Then the efficiency of the transformer is:

1. 11%
2. 50%
3. 80%
4. 90%

✅ Correct Answer: 4

The magnetic flux (∅) linked with a coil is related to the number of turns (N) ofthe coil as:

1. f ∝ N
2. f ∝ N-1
3. f ∝ N2
4. f ∝ N-2

✅ Correct Answer: 1

The magnetic flux (∅) lined with a coil is related to its area (s) as:

1. ∅ ∝ s
2. ∅ ∝ s²
3. ∅ ∝ s1/2
4. ∅ ∝ s-1/2

✅ Correct Answer: 1

If the magnetic flux linked with a coil through which a current off ampere is set up is ∅, then the coefficient of self-inductance of the coil is:

1. l/∅
2. ∅/l
3. ∅l
4. None of the above

✅ Correct Answer: 2

The role of inductance is equivalent to:

1. inertia
2. force
3. energy
4. momentum

✅ Correct Answer: 1

A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 rad s-1 . If the horizontal component of earth’s magnetism is 2 × 10-5 T, then e.m.f. developed between the two ends of the conductor is:

1. 5 µV
2. 50 µV
3. 5 mV
4. 50 mV

✅ Correct Answer: 1

coil of L = 8.4 mH and R = 6 Ω is connected to a 12 V battery. The current in the coil is 1.0 A at approx’time of:

1. 500 s
2. 20 s
3. 35 ms
4. 1 ms

✅ Correct Answer: 4

If I current is flowing inductance L, then the dimension of 32 LI² is equivalent to:

1. charge
2. force
3. momentum
4. energy

✅ Correct Answer: 3

The phase difference between the flux linkage and the emf in a rotating coil in a uniform magnetic field is:

1. zero
2. π/2
3. π/4
4. π

✅ Correct Answer: 3

A choke is used as a resistance in :

1. dc circuits
2. ac circuits
3. both ac and dc circuits
4. neither (a) nor (b)

✅ Correct Answer: 2

The SI unit of magnetic flux is:

1. T
2. Tn-2
3. Wb
4. Wb m-2

✅ Correct Answer: 3

For purely capacitive circuits, power factor is:

1. 0
2. -1
3. 1
4. infinity

✅ Correct Answer: 1

The magnetic flux linked with a coil is inversely proportional to the?

1. magnetic field
2. area of cross section
3. number of turns
4. None of the above

✅ Correct Answer: 1

When the magnetic field is parallel to a surface, then the magnetic flux through the surface is:

1. infinite
2. zero
3. small but not zero
4. large but not infinite.

✅ Correct Answer: 2

The energy stored in a 50 mH inductor carrying a current of 4 A is:

1. 0.1 J
2. 0.4 J
3. 0.04 J
4. 0.01 J

✅ Correct Answer: 2

The flux linked with a coif at any instant t is given by ∅ = 10t² – 50t + 250. The induced emf at t = 35 is:

1. 10 V
2. 190 V
3. -190
4. -10 V

✅ Correct Answer: 4

Two coils of self inductance 2 mil and 8 mil are placed so close together that the effective flux in one coil is completely linked with other. The mutual inductance between these coils is :

1. 4 mH
2. 16 mH
3. 10 mH
4. 6 mH

✅ Correct Answer: 3

The core of a transformer is laminated because:

1. rusting of core may be prevented
2. ratio of voltage in primary and secondary may be increased.
3. energy losses due to eddy current may be minimised
4. The weight of transformer may be reduced

✅ Correct Answer: 3