The property of an AC circuit that resists any change in voltage due to energy storage in a capacitor is called what?

• A. Capacitive reactance (capacitance)
• B. Inductive reactance (inductance)
• C. Resistance
• D. Conduction

Answer: (A)

Capacitors store energy in an electric field and, in an AC circuit, this storage resists rapid changes in voltage. The measure of that opposition to voltage changes is capacitive reactance, which depends on frequency and capacitance (Xc = 1/ωC). Higher frequencies lower the reactance, so the capacitor passes AC more easily at higher frequencies, while lower frequencies increase the reactance and the capacitor opposes the voltage change more. This concept is specific to capacitors; inductors produce inductive reactance, plain resistance is not tied to energy storage in the same way, and conduction isn’t the term for this behavior.