Which term describes the opposition to AC flow caused by inductance and capacitance?

Which term describes the opposition to AC flow caused by inductance and capacitance?

• A. Resistance
• B. Reactance
• C. Impedance
• D. Conductance

Answer: (C)

In AC circuits, the opposition to current isn’t just about a material’s resistance; inductors and capacitors store and release energy, causing a phase shift between voltage and current. The term that describes the total opposition to AC flow, taking into account both the resistive losses and the reactive effects from inductance and capacitance, is impedance. Impedance is a complex quantity Z = R + jX, where R is the real, resistive part and X is the net reactance from L and C (X = X_L − X_C, with X_L = ωL and X_C = 1/(ωC), the capacitor part being negative). The magnitude |Z| tells you how much the current is overall opposed, and the phase angle φ = arctan(X/R) tells you how voltage and current are shifted relative to each other. So impedance is the appropriate umbrella term because it fully describes how AC current is opposed by both energy-storing elements and resistive losses.

In AC circuits, the opposition to current isn’t just about a material’s resistance; inductors and capacitors store and release energy, causing a phase shift between voltage and current. The term that describes the total opposition to AC flow, taking into account both the resistive losses and the reactive effects from inductance and capacitance, is impedance. Impedance is a complex quantity Z = R + jX, where R is the real, resistive part and X is the net reactance from L and C (X = X_L − X_C, with X_L = ωL and X_C = 1/(ωC), the capacitor part being negative). The magnitude |Z| tells you how much the current is overall opposed, and the phase angle φ = arctan(X/R) tells you how voltage and current are shifted relative to each other. So impedance is the appropriate umbrella term because it fully describes how AC current is opposed by both energy-storing elements and resistive losses.