Explain the phenomenon of electromagnetic induction. Describe an experiment to show that a current is set up in a closed loop when an external magneic field passing through the loop increases or decreases.

Explanation

Electro-magnetic induction : This was first demonstrated by Michel Faraday in 1831. When a conductor and magnetic field are in motion relative to each other , electric current in induced in the condcutor. This phenomenon is called electromagnetic induction.
Experiment :

(i) Take two coils with large number of turns . Let us assume that number of turns in one coil is 100 and in another coil it is 50.
(ii) Insert a cylinder of a non-conducting material through these coils.
(iii) Connect the coil with 50 turns to a galvanometer.
(iv) Connect the coil with 100 turns to a battery and plug key.
Observation :
(v) When key is switched on deflectioon is seen in galvnometer.
(vi) When key is switched off, deflection is seen in galvanometer, but in opposite direction.
(vii) this shows that whenever there is a change in stregnth of magnetic field, current is induced in the coil.