Which statement best describes impedance in AC circuits?

• A. It is the total opposition to current flow, combining resistance and reactance
• B. Only resistance
• C. Only inductive reactance
• D. Only capacitive reactance

Answer: (A)

In AC circuits, impedance is the total opposition to current flow, coming from both the resistive part and the reactive part. The resistive part dissipates energy as heat, while the reactive part stores and returns energy through inductors (inductive reactance) and capacitors (capacitive reactance). These reactive effects depend on frequency and together with resistance form a complex quantity Z = R + jX, where X accounts for the net reactance (X = X_L − X_C). Because of this combination, impedance describes not just how much the current is opposed, but also how the voltage and current relate in phase. So the statement that best describes impedance is that it is the total opposition to current flow, combining resistance and reactance.