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
- 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
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 galvanometer will be observed which will die out soon when the current flowing through first coil attains steady state.
Due to similar phenomenon, a momentary deflection is again observed in opposite direction when key is removed as in this case current is decreasing in the circuit.
The correct option is D.