The product of RMS voltage and RMS current in an AC circuit is called:

• A. Real Power
• B. Reactive Power
• C. Power Factor
• D. Apparent Power

Answer: (D)

In AC circuits, the product of RMS voltage and RMS current defines apparent power. This quantity, S, represents the total power flow in the circuit without regard to the phase difference between voltage and current, and it’s measured in volt-amperes (VA) as S = Vrms × Irms.

Real power, P = Vrms × Irms × cos(phi), is the portion actually delivered as useful work (watts). Reactive power, Q = Vrms × Irms × sin(phi), represents energy stored and returned by reactive elements (volt-ampere reactive, vars). The relationship among them forms a power triangle where S^2 = P^2 + Q^2, and cos(phi) = P/S, sin(phi) = Q/S. When the circuit is purely resistive (phi = 0), all power is real and S = P; when it’s purely reactive (phi = 90°), P = 0 and S = |Q|. Thus, the product of RMS voltage and RMS current is the apparent power.