Drop in EMF caused by Inductance is proportional to Rate of Change of Current

Physical Law
The drop in EMF $E_L$ caused by an inductor is proportional to the rate of change of current $I$ through the inductor:
 * $E_L = L \dfrac {\mathrm d I} {\mathrm d t}$

The constant of proportion $L$ is known as the inductance of the inductor.