What term describes the opposition to alternating current flow?

The term that describes the opposition to alternating current (AC) flow is impedance. Impedance is a comprehensive measure that combines both resistance and reactance in an AC circuit. It is expressed in ohms and accounts for the effects of both resistive components (which oppose current flow) and reactive components, including inductance and capacitance, which store and release energy.

In an AC system, impedance becomes especially important because it varies with the frequency of the current. Resistance, on its own, applies mainly to direct current (DC) and does not encompass the effects of inductance and capacitance, which are crucial in AC circuits. Inductance refers specifically to the opposition due to inductors, while capacitance relates to capacitors. Both contribute to the total opposition in an AC system but in a manner that is distinct from pure resistance. Thus, impedance is essential for analyzing and understanding how AC circuits behave under various conditions.