Whenever there is a change in the magnetic flux linked with a closed circuit an emf is produced. This emf is known as the induced emf and the current that flows in the closed circuit is called induced current.
The phenomenon of producing an induced emf due to the changes in the magnetic flux associated with a closed circuit is known as electromagnetic induction.
Faraday discovered the electromagnetic induction by conducting several experiments.
Fig: Electromagnetic Induction
Figure consists of a cylindrical coil C made up of several turns of insulated copper wire connected in series to a sensitive galvanometer G. A strong bar magnet NS with its north pole pointing towards the coil is moved up and down. The following inferences were made by Faraday.
(i) Whenever there is a relative motion between the coil and the magnet, the galvanometer shows deflection indicating the flow of induced current.
(ii) The deflection is momentary. It lasts so long as there is relative motion between the coil and the magnet.
(iii) The direction of the flow of current changes if the magnet is moved towards and withdrawn from it.
(iv) The deflection is more when the magnet is moved faster, and less when the magnet is moved slowly.
(v) However, on reversing the magnet (i.e) south pole pointing towards the coil, same results are obtained, but current flows in the opposite direction.