CBSE Class 12 Physics Electromagnetic Induction Objective Questions

CBSE Class 12 Physics Electromagnetic Induction Objective Questions. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

1. When the number of turns and the length of the solenoid are doubled keeping the area of cross-section same, the inductance
(a) remains the same (b) is halved (c) is doubled (d) becomes four times.

2. A coil of 10 cm × 10 cm having 50 turns is making 50 r.p.s. in a magnetic field of induction 2 tesla. The peak value of induced e.m.f. is approximately
(a) 110 volt (b) 220 volt (c) 314 volt (d) 628 volt

3. Two coils X and Y are placed in a circuit such that a current changes by 3 ampere in coil X and the magnetic flux changes of 1.2 weber occurs in Y. The value of mutual inductance of the coil is
(a) 0.2 H (b) 0.4 H (c) 0.6 H (d) 3.6 H

4. A coil of area 100 cm² having 50 turns is perpendicular to a magnetic field of intensity 0.02 weber/m². The resistance of the coil is 2 Ω. If it is removed in 1 sec. from the magnetic field, the induced charge produced is
(a) 5 C (b) 0.5 C (c) 0.05 C (d) 0.005 C

5. A force of 10 N is required to move a conducting loop through a non-uniform magnectic field at 2 m/s. The rate of change of internal energy in watt in loop is
(a) 5 (b) 10 (c) 15 (d) 20

6. A coil of conducting wire of radius r has 600 turns and a self inductance of 108 mH. The self inductance of a similar coil of 500 turns will be
(a) 75 mH (b) 108 mH (c) 90 mH (d) 62.5 mH

7. Two pure inductor coils of self inductance L each are connected in series, the net inductance is
(a) L (b) 2 L (c) L/2 (d) L/4

8. An aeroplane is flying horizontally with a velocity of 360 km/hr. The distance between the tips of wings is 50 m. If the vertical component of earth’s magnetic field is 4 x 10^–4 T, induced e.m.f. is
(a) zero (b) 2μ V (c) 2 mV (d) 2 V

9. A circular ring of diameter 20 cm has a resistance 0.01 ohm. How much charge will flow through the ring if it is rotated from position perpendicular to the uniform magnetic field of B = 2 T to a position parallel to field ?
(a) 4 C (b) 6.28 C (c) 3.14 C (d) 25.12 C

10. A rectangular loop with a sliding connector of length 10 cm is situated in a uniform magnetic field perpendicualr to plane of the loop. The magnetic induction is 0.1 T and resistance of connector is 1 ohm. The sides A B and C D have resistances 2 ohm and 3 ohm respectively. Find the current in the connector during its motion with constant velocity of one metre/sec.

(a) 1/220 A(b) 1/110A  (c) 1/440A (d) 1/55A

11. Two different coils have self inductances L₁ = 8 mH, L₂ = 2 mH. The current in one coil is increased at a constant rate. The current in the second coil is also increased at the same constant rate. At a certain instant of time, the power given to the two coils is the same. At that time the current, the induced voltage and the energy stored in the first coil are i₁, V₁ and W₁ respectively. Corresponding values for the second coil at the same instant are i₂, V₂ and W₂ respectively. Then which answer is not correct
(a) i₁/i₂ = 1/4 (b)i₁/i₂ = 4 (c) W₂/W₁ = 4 (d) V₂/V₁ = 1/4

12. The ratio of secondary to the primary turns in a transformer is 5. If the output voltage be P, the input voltage neglecting all losses, must be equal to
(a) 5 P (b) √5 P (c) P/5 (d) P/ 5

13. A rectangular coil of 100 turns and size 0.1 m x 0.05 m is placed perpendicular to a magnetic field of 0.1 T. If the field drops to 0.05 T in 0.05 s, the magnitude of the e.m.f. induced in the coil is
(a) 0.5 V (b) 0.75 V (c) 1.0 V (d) 1.5 V

14. A coil of area 10 cm², 10 turns and resistance 20 Ω is placed in a magnetic field directed perpendicular to the plane of the coil and changing at the rate of 10⁸ gauss/second. The induced current in the coil will be
(a) 5 A (b) 0.5 A (c) 0.05 A (d) 50 A

15. A coil of cross-sectional area 400 cm² having 30 turns is making 1800 rev/min in a magnetic field of 1 T. The peak value of the induced e.m.f. is
(a) 113 V (b) 226 V (c) 339 V (d) 452 V

16. A soleniod has 2000 turns wound over a length of 0.3 m. Its cross-sectional area is 1.2 × 10^–3 m². Around its central section a coil of 300 turns is wound. If an initial current of 2 A flowing in the solenoid is reversed in 0.25 s, the e.m.f induced in the coil will be
(a) 6.0 × 10^–4 V (b) 6.0 × 10^– 2V (c) 4.8 × 10^–4 V (d) 4.8 × 10^–2 V

17. A square metal loop of side 20 cm and resistance 2 ohm is moved with a constant velocity partly inside
a uniform magnetic field of 5 Wb/m², directed into the paper, as shown in the figure. The loop is
connected to a network of five resistors each of value R. If a steady current of 0.1 A flows in the loop,
and the speed of the loop is 1 m/s, then R is equal to

(a) 2 Ω (b) 3 Ω (c) 8 Ω (d) 9 Ω

18. A rectangular coil of single turn, having area A, rotates in a uniform magnetic field B with an angular velocity ω about an axis perpendicular to the field. If initially the plane of the coil is perpendicular to the field, then the average induced e.m.f. when it has rotated through 900 is
(a)  ωBA/π  (b)  ωBA/2π (c) ωBA/4π (d) ωBA/2π

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