1. In electromagnetic induction, the induced charge in a coil is independent of

(a) change in the flux                                (b) time taken to change the flux

(c) resistance in the circuit                    (d) None of the above

2. A magnet is brought towards a coil (i) speedly (ii) slowly, then the induced emf/induced charge will be respectively

(a) more in first case/more in first case     (b) more in first case/equal in both cases

(c) less in first case/more in second case (d) less in first case/equal in both cases

3. In a coil of area 10 cm2 and 10 turns with a magnetic field directed perpendicular to the plane and is changing at the rate of 108 gauss/s. The resistance of the coil is 20 Ω. The current in the coil will be

(a) 5 A                 (b) 0.5 A

(c) 0.05 A          (d) 5 108 × A

4. 4. A coil having 500 square loops each of side 10 cm is placed normal to a magnetic flux which increases at the rate of 1.0 T/s. The induced emf in volts is

(a) 0.1                     b) 0.5

(c) 1                          (d) 5

5. A coil having an area 2 m2 is placed in a magnetic field which changes from 1 Wb/m 2 to 4 Wb/m 2 in an interval of 2 s. The emf induced in the coil will be

(a) 4 V                         (b) 3 V

(c) 1.5 V                      (d) 2 V

6. A coil of 40 Ω resistance, 100 turns and radius 6 mm is connected to ammeter of resistance 160 Ω. Coil is placed perpendicular to the magnetic field. When coil is taken out of the field, 32 μC charge flows through it. The intensity of magnetic field will be

(a) 6.55 T                    (b) 5.66 T

(c) 2.55 T                       (d) 0.566 T

7. The magnetic flux linked with a coil, in webers, is given by the equation φ = + + 3 4 9 2 t t . Then, the magnitude of induced emf at t = 2 s will be

a) 2 V                           (b) 4 V

(c) 8 V                          (d) 16 V

8. A coil has an area of 0.05 m 2 and it has 800 turns. It is placed perpendicularly in a magnetic field of strength 4 10 5 × − Wb/m 2 , it is rotated through 90° in 0.1 s. The average emf induced in the coil is

(a) 0.056 V                       (b) 0.046 V

(c) 0.026 V                       (d) 0.016 V

11.11. The resistance and inductance of series circuit are 5 Ω and 20 H respectively. At the instant of closing the switch, the current is increasing at the rate 4 A/s. The supply voltage is

(a) 20 V                                    (b) 80 V

(c) 120 V                                   (d) 100 V

12. 12. The number of turns in the coil of an AC generator is 5000 and the area of the coil is 0.25 m 2 . The coil is rotated at the rate of 100 cycles/s in a magnetic field of 0.2 W/m 2 . The peak value of the emf generated is nearly

(a) 786 kV                             (b) 440 kV

(c) 220 kV                              (d) 157.1 kV

13. 13. Two coils have a mutual inductance 0.005 H. The current changes in the first coil according to equation I I t = 0 sin , ω where I 0 = 10 A and ω π = 100 rad/s. The maximum value of emf in the second coil is (in volt)

(a) 2π                                         (b) 5π

(c) π                                             (d) 4π

22.When the current through a solenoid increases at a constant rate, the induced current

(a) is a constant and is in the direction of the inducing current

(b) is a constant and is opposite to the direction of the inducing current

(c) increase with time and is in the direction of inducing current

(d) increase with time and is opposite to the direction of inducing current

23. The direction of induced emf during electromagnetic induction is given by

(a) Faraday’s law

(b) Lenz’s law

(c) Maxwell’s

(d) Ampere’s law

24. Two different loops are concentric and lie in the same plane. The current in the outer loop is clockwise and increasing with time. The induced current in the inner loop then, is

(a) clockwise

(b) zero

(c) counter clockwise

(d) in a direction that depends on the ratio of the loop radii

25.Lenz’s law is due to conservation of

(a) charge

(b) momentum

(c) energy

(d) current

26. The circular loops of equal radii are placed coaxially at some separation. The first is cut and a battery is inserted in between to drive a current in it. The current changes slightly because of the variation in resistance with temperature. During this period, the two loops

(a) attract each other

(b) repel each other

(c) do not exert any force on each other

(d) attract or repel each other depending on the sense of the current

27. A small, conducting circular loop is placed inside a long solenoid carrying a current. The plane of the loop contains the axis of the solenoid. If the current in the solenoid is varied, the current induced in the loop is

(a) clockwise

(b) anti-clockwise

(c) zero

(d) clockwise or anti-clockwise depending on whether the resistance is increased or decreased

29. When a magnet with its magnetic moment along the axis of a circular coil and directed towards the coil is withdrawn away from the coil, parallel to itself, the current in the coil, as seen by the withdrawing magnet is

(a) zero

(b) clockwise

(c) anti-clockwise

(d) None of the above

45. A 50 mH coil carries a current of 2 A. The energy stored in joules is

(a) 1

(b) 0.1

(c) 0.05

(d) 0.5