question_answer 22)

  Same as problem 4 except the coil A is made to rotate about a vertical axis, Fig. 4(EP).3. No current flows in B it A is at rest. The current in coil A, when the current in B (at t = 0) is counterclockwise and the coil A is as shown at this istant, t = 0, is (a) constant current clockwise (b) varying current clockwise (c) varying current counterclockwise (d) constant current counterclockwise

Answer:

  (a)When current in coil B (at t = 0) is counterclockwise, constant current in A (at t = 0) must be clockwise. Therefore, when coil A is made to rotate about a vertical axis, it would induce current in coil B in clockwise direction, as per Lenz's law. Choice (a) is correct.