Question

In the arrangement shown in Figure  there are two coils wound on a non-conducting cylindrical rod. Initially the key is not inserted. Then the key is inserted and later removed. Then

Options

• the deflection in the galvanometer remains zero throughout

• there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed

• there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction

• there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

Answer 1

there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

Explanations - 

As the current in the first coil changes, the magnetic field associated with it also changes. Thus the magnetic field lines around the other coil also change. Hence the change in magnetic field lines associated with the secondary coil is the cause of induced electric current in it by the process of electromagnetic induction. Due to this reason, a momentary deflection in the galvanometer will be observed which will die out soon when the current flowing through the first coil attains a steady state.

Due to a similar phenomenon, a momentary deflection is again observed in the opposite direction when the key is removed.