Which term describes the opposition to AC flow produced by inductance or capacitance?

• A. Ratio
• B. Reactance
• C. Saturation
• D. Retentivity

Answer: (B)

Reactance is the opposition to AC flow produced by inductance or capacitance. In AC circuits, inductors resist changes in current and capacitors resist changes in voltage, so they store energy and create a phase difference between current and voltage. This opposition depends on frequency: inductive reactance grows with frequency (X_L = ωL), making inductors oppose high-frequency signals more, while capacitive reactance falls with frequency (X_C = 1/ωC), making capacitors oppose high-frequency signals less as frequency increases. The overall impact in a circuit is described by impedance, whose imaginary part is the net reactance (X_L minus X_C). The other terms—ratio, saturation, and retentivity—do not describe this frequency-dependent opposition arising from energy-storing elements.