Describe the coil and barmagnet experiment to demonstrate the phenomenon of electromagnetic induction.

Explanation

(a) Magnet and coil experiment: 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 If the magnet is withdrawn suddenly, a sudden deflection is again observed but in the opposite direction. The deflection is greater if the magnet is introduced or withdrawn quickly.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 there is no relative motion between the coil and the magnet.

(b) Coil and coil experiment: Consider two coils Pand Placed close 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 deflection 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 of rest.