(a) A galvanometer is an instrument that can detect the presence of a current in a circuit. The pointer remains at zero (the centre of the scale) for zero current flowing through it. Pointer can deflect either to the left or to the right of the zero-mark depending on the direction of current. There is a momentary deflection in the needle of the galvanometer to the right. This indicates the presence of a current in the coil AB. The deflection becomes zero the moment the motion of the magnet stops.