question_answer 21)

  There are two coils A and B as shown in Fig. 4(EP).2. 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 counter- clockwise. B is kept stationary when A moves. We can infer that (a) there is a constant current in the clockwise direction in A (b) there is a varying current in A (c) there is no current in A (d) there is a constant current in the counter- clockwise direction in A

Answer:

  (d)Coil A must be carrying a constant current in counter clockwise direction. That is why when A moves towards B, current induced in B is in counter clockwise direction, as per Lenz's law. The current in B would stop when A stops moving. Choice (d) is correct.