In AC power analysis, the quantity measured in volt–amperes (VA) is referred to as which type of power?

Introduction / Context:
AC circuits with reactance exhibit a distinction between power that performs real work and power that circulates between source and reactive elements. Proper terminology—true, reactive, and apparent power—is foundational for sizing equipment and understanding power factor.

Given Data / Assumptions:

• Sinusoidal steady-state assumptions.
• Voltage and current may be out of phase by angle phi due to reactance.
• Standard definitions of power components.

Concept / Approach:
Apparent power S is defined as S = V_rms * I_rms and is measured in volt–amperes (VA). True (real) power P = V_rms * I_rms * cos(phi) is measured in watts (W). Reactive power Q = V_rms * I_rms * sin(phi) is measured in volt–ampere reactive (VAR). Thus, when an instrument reports results in VA, it is indicating apparent power.

Step-by-Step Solution:
Identify units: VA corresponds to S = V_rms * I_rms.Relate to P and Q: P in watts, Q in VAR, S in VA.Therefore, the power measured in volt–amperes is apparent power.

Verification / Alternative check:
Power triangle relationships: S^2 = P^2 + Q^2. Instruments like apparent power meters or nameplate ratings for transformers/UPS specify VA because they must supply the vector sum capacity regardless of power factor.

Why Other Options Are Wrong:

• Impedance power: Not a standard term in AC power theory.
• Reactive power: Measured in VAR, not VA.
• True power: Measured in watts.

Common Pitfalls:

• Confusing VA with W; at unity power factor, VA equals W, but the units and concept remain distinct.
• Using VA ratings to assume real work capability without considering power factor.

Final Answer:
apparent power