FARADAY'S EXPERIMENTS OF ELECTROMAGNETIC INDUCTION

Faraday took a ring of soft iron. On one side of it, an insulated conducting coil was connected with a battery. On the opposite side, another conducting
coil was connected with a galvanometer.
Faraday observed that passing a steady current through the left coil produced no effect on the galvanometer in the right coil. However, a momentary deflection of galvanometer was noticed whenever the battery was switched on or off. When a steady current is passed magnetic flux produced in the left coil passes through the right coil which does not produce any current in it. Whenever the battery is switched on or off, magnetic flux in the right coil changes from zero to maximum or maximum to zero
respectively. This rate of change of magnetic flux in the right coil produces current in it. In another experiment, Faraday arranged two bar magnets in the shape of V. At the open end of V, he kept one soft iron rod with an insulated copper wire wound around it to which galvanometer was connected. On moving the upper magnet up and down, galvanometer showed deflection. Magnetic flux through the coil increased when the magnet touched  the iron rod and decreased when it moved away. Faraday concluded from these experiments that ‘To produce electric field in a coil, the change in magnetic flux is important and not the flux itself.’
Faraday also noted that:
( i ) More current is produced when the magnet is moved faster due to faster change of
magnetic flux linked with the coil.
( ii ) When a coil carrying electric current is placed  above another coil and relative motion produced between the two coils, galvanometer shows  deflection in the other coil.
( iii ) If any of the two coils is rotated with respect to the other, then also galvanometer shows deflection.
( iv ) If the north pole of a bar magnet is
moved towards a coil, the galvanometer
shows deflection. Now if the magnet is
moved away from the coil, the galvanometer
shows deflection in the opposite direction.
Similar results are obtained with the south pole of  the magnet with deflections of galvanometer in  opposite direction.
Faraday named the current produced as the ‘induced current’, the emf as ‘induced emf’ and the phenomenon as ‘magnetic induction’.