What is the primary function of an inductor in a circuit?

The primary function of an inductor in a circuit is to oppose changes in current. Inductors achieve this by generating a magnetic field around themselves when current flows through them. This property is rooted in Lenz's Law, which states that the direction of induced electromotive force (EMF) is such that it opposes the change in current that created it. As a result, if the current through an inductor increases, the inductor will generate an opposing voltage to counter that change, and if the current decreases, it will act to keep the current flowing.

This characteristic makes inductors essential in various applications, such as in filters, oscillators, and power supply circuits, where managing current flow is crucial. In circuits where stability and control of current are required, inductors play a vital role by smoothing out fluctuations, thereby ensuring more consistent performance.

The other options provide functions that may or may not directly involve an inductor's fundamental role in opposing current changes, but they do not capture the essential purpose of an inductor as effectively as the correct choice does.