What does the term "reactance" refer to in an AC circuit?

The term "reactance" in an AC circuit specifically refers to the opposition that capacitors and inductors present to the flow of alternating current. This opposition is not due to resistance but rather to the stored energy in these components.

Capacitors store energy in the form of an electric field, while inductors store energy in a magnetic field. The unique properties of capacitors and inductors cause the current and voltage to be out of phase with each other, resulting in a kind of opposition that is frequency-dependent. This means that reactance varies with the frequency of the AC signal, a crucial aspect to consider when analyzing AC circuits.

Understanding reactance is essential when designing circuits because it impacts the overall impedance, which is the total opposition to current flow in an AC system, and thus affects performance, efficiency, and power factor in electrical systems.