(a) Electromagnetic induction: whenever there is change in number of magnetic field lines associated with conductor. an electromotive force is developed between the ends of the conductor which lasts as long as the change is taking place. 

(b) Demonstration of the phenomenon of electromagnetic induction :

In the figure :

(i) When the magnet is stationary there is no deflection in galvanometer. The pointer read zero. [Fig. (a)] 

(ii) when the magnet with north pole facing the solenoid is moved towards the solenoid. the galvanometer shows a deflection towards the right showing that a current flows in the solenoid in the direction as shown in [Fig (b)] 

(iii) As the motion of magnet stops, the pointer of the galvanometer comes to the zero position [Fig (c)]. This shows that the current in the solenoid flows as long as the magnet is moving. 

(iv) If the magnet is moved away from the solenoid, the current again flows in the solenoid, but now in a direction opposite to that shown in [Fig. (b)] and therefore the pointer of the galvanometer deflects towards left[ Fig. (d)]. 

(v) If the magnet is moved away rapidly i.e. with more velocity, the extent of deflection in the galvanometer increases although the direction of deflection remains the same. It shows that more current flows now. 

(vi) If the polarity of the magnet is reversed and then the magnet is brought towards the solenoid, the current in solenoid flows in the direction opposite to that shown in Fig (b) and so the pointer of galvanometer deflect towards left [Fig. (e)].