Describe expriments to demonstrate electromagnetic induction.

Explanation

(a) Magnet and coil expriment : If one end of a magnet is suddenly introduced into a coil connected to a sensitive galvanometer it shows a momentary deflection.
This shows that a momentary current and hence an instantaneous emf is produced in the circuit and the direction of the current depends on the pole towards the coil. The current produced is called induced current. if the magnet is withdrawn suddenly ,a sudden deflection is again observed but in the opposite direction. The deflection is greater if the magnet is introduced or withdrawn quickly. No induced emf is obtained when threre is no relative motion between the coil and the magnet.

(b) Coil and coil experiment : Consider two coils P and S placed closed to each other.
Coil P connected to a cell through a key Sw is called the primary coil. The other coil S connected in series with a sensitive galvanometer G is called the secondary coil.
On pressing Sw a momentary defluction is noticed in the galvanometer. When the key is released the galvanometer deflects in the opposite direction. However, no induced emf is obtained when a steady current flows through the primary, as long as the secondary coil is at rest.