The property of a coil which enables to produce an opposing induced emf in it when the current in the coil changes is called self induction.
A coil is connected in series with a battery and a key (K) (Figure). On pressing the key, the current through the coil increases to a maximum value and correspondingly the magnetic flux linked with the coil also increases. An induced current flows through the coil which according to Lenz’s law opposes the further growth of current in the coil.
On releasing the key, the current through the coil decreases to a zero value and the magnetic flux linked with the coil also decreases. According to Lenz’s law, the induced current will oppose the decay of current in the coil.