Changing current in an inductor gives rise to self induced emf which opposes changes in the current flowing through the inductor.
This self inductance thus plays the role the inertia and it is electromagnetic analogue of mass in mechanics.
So a certain amount of work is required to be done against this self induced emf for establishing the current in the circuit.
In order to do so, the source supplying current in a circuit must maintain Potential difference between its terminals which is done by supplying energy to the inductor.
Power supplied to the inductor is given by relation
P=ξI ---(4)
where
L is Self inductance and
dI/dt is rate of change of current I in the circuit.
Energy dW supplied in time dt would be
dW=Pdt
=LI(dI/dt) dt
=LIdI
and total energy supplied while current I increases from o to a final value I is
Once the current reaches its final value and becomes steady ,the power input becomes zero.
The energy so far supplied to the inductor is stored in it as a form of potential energy as long as current is maintained.
When current in circuit becomes zero, the energy is returned to the circuit which supplies it.