question_answer

  Describe an experiment to show that a current is set up in a closed loop when an external magnetic field passing through the loop increases or decreases.

Answer:

                  Let two different coils of copper wire, namely coil 1 and coil 2, having large number of turns are arranged as per the circuit diagram (as shown in figure). The coil 1, having larger number of turns, is connected in series with a battery and a plug key whereas the other coil 2 is connected with a galvanometer.   Case I When key K is closed, the galvanometer shows a deflection in its needle instantly jumps to one side and just as quickly returns to zero, indicating a momentary current in coil 2. This happens due to an external magnetic field passing through the loop increases. Case II When key K is open, the coil 1 is disconnected from the battery. The needle momentarily moves, but to the opposite side. It means that now the current flows in the opposite direction in coil 2. This happens due to an external magnetic field passing through the loop decreases.                                       (2)