# Energy in inductor

## Energy in an inductor

- 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.