When does an inductor act as a temporary voltage source?

An inductor acts as a temporary voltage source when current is interrupted. This behavior is due to the fundamental principle of inductance, which is the tendency of an inductor to oppose changes in the current flowing through it. When current through an inductor is steady and then suddenly interrupted, the inductor generates a voltage in an attempt to maintain the current flow. This happens because the inductor stores energy in its magnetic field when current flows through it. If the circuit is suddenly opened or the current abruptly stops, the magnetic field collapses, releasing the stored energy and inducing a voltage. This induced voltage can be significant enough to drive current in the circuit briefly, effectively acting as a temporary voltage source.

In this context, while the other scenarios do provide different operational states of the inductor, they do not involve the same fundamental principles of sudden current interruption leading to the creation of a voltage. In a closed circuit, the inductor operates normally without the context of storing energy for temporary voltage supply. Similarly, during steady current flow, there are no abrupt changes that induce a reactive voltage. A constant voltage does not directly relate to the function of the inductor as a voltage source reacting to change.