Inductance

DC current flowing through any inductor has a tendency to maintain itself. Inductance basically determines how quickly current can change. When the resistance along a path with an inductor suddenly increases, inductance makes it impossible for the current to drop as suddenly. As a result, the current drops as a function of many factors, including inductance. Often, current drops slower than the increase of resistance. As a result, a large electrical potential is developed across the points where there is a sharp increase of resistance.