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