M.C.Q : Electromagnetic Induction ( 1 to 10)

LEVEL – I

1. An inductor coil of inductance L is divided into two equal parts and both parts are connected in parallel. The net inductance is :

(A) L

(B) 2L

(C) L/2

(D) L/4

2. An e.m.f. of 5 millivolt is induced in a coil when in a nearby placed another coil, the current changes by 5 ampere in 0.1 second. The coefficient of mutual induction between the two coils will be :

(A) 1 Henry

(B) 0.1 Henry

(C) 0.1 millihenry

(D) 0.001 millihenry

3. In figure when key is pressed the ammeter A reads i ampere. The charge passing in the galvanometer circuit of total resistance R is Q. The mutual inductance of the two coils is :

(A) Q/R

(B) QR

(C) QR/i

(D) i/QR

4. The equivalent inductance between points P and Q in figure is :

(A) 2 H

(B) 6 H

(C) 8/3 H

(D) 4/9 H

5. A metal disc of radius R rotates with an angular velocity ω about an axis perpendicular to its plane passing through its centre in a magnetic field of induction B acting perpendicular to the plane of the disc. The induced e.m.f. between the rim and axis of the disc is:

(A) BπR2

(B) 2Bπ2R2

(C) BπR2ω

(D) BR2ω/2

6. In the circuit shown in the adjoining diagram E = 10 volts, R1 = 2 ohms, R2 = 3 ohms, R3 = 6 ohms and L = 5 henry. The current i1 just after pressing the switch S is :

(A) 2.5 amp

(B) 2 amp

(C) 5/6 amp

(D) 5/3 amp

7. A rectangular coil pqrs is moved away from an infinite, straight wire carrying a current as shown in figure. Which of the following statements is correct?

(A) There is no induced current in coil pqrs

(B) The induced current in coil pqrs is in the clockwise sense

(C) The induced current in the coil pqrs is in anticlockwise direction

(D) None of the above

8. The switch S is closed in the circuit shown at time t = 0. The current in the resistor at t = 0 and t = ∞ are respectively.

(A) 0, 0 Amp.

(B) 1, 0 Amp.

(C) 0, 1 Amp.

(D) 1, 1 Amp.

9. The two loops shown in the figure, have their planes parallel to each other. A clockwise current flows in the loop X as viewed from X towards Y. The two coils will repel each other, if the current in the loop X is :

(A) increasing

(B) decreasing

(C) constant

(D) none of the above cases

10. A coil of area 500 cm2 having 1000 turns is placed such that the plane of the coil is perpendicular to a magnetic field of magnitude 4 × 10-5 weber/m2. If it is rotated by 180° about an axis passing through one of its diameter in 0.1 sec, find the average induced emf.

(A) zero.

(B) 30 mV

(C) 40 mV

(D) 50 mV

ANSWER:

1. (D)    2. (C)   3. (C)    4. (A)   5. (D)    6. (B)   7. (B)    8. (D)   9. (A)    10. (C)

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