question_answer 32)

  Consider a metal ring kept (supported by a cardboard) on top of a fixed solenoid carrying a current , Fig. 4(EP).6. The centre of the ring coincides with the axis of the solenoid. If the current in the solenoid is switched off, what will happen to the ring?

Answer:

                  In the same Fig. 4(EP).6, when current in the solenoid is suddenly switched off, magnetic flux linked with the solenoid and hence with metal ring decreases. Current induced in the metal ring is clockwise, i.e., in the same direction as the solenoid current. They will attract each Other. The metal ring, therefore, will remain on the cardboard. However, reaction of cardboard on the ring will increase.