Energy stored in an inductor

Let us turn our attention to power and energy consideration for an inductor. The instantaneous power absorbed by the inductor is expressed by product of the current through inductor i(t ) and the voltage across it v(t).

Since the energy is the product of power and time, the energy absorbed by an inductor over a period is expressed as

Example

Figure shows the plot of current i(t) through a series R − L circuit when a constant forcing function of magnitude Vs = 50 V is applied to it. Calculate the values of resistance R and inductance L .

                                              Current -Ys time characteristic

Solution:

Figure one can easily see that the steady state current flowing through the circuit is 10 A and the time constant of the circuit τ = 0.3 sec. The following relationships can be written as