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In an AC circuit, the reactive power Q<sub>r</sub> = V<sub>rms</sub> I<sub>rms</sub> sin(φ) is measured in:

Answer: VAR (volt-ampere reactive).

  • A VAR (volt-ampere reactive)
  • B Watts as frequently observed in practice
  • C VA (volt-ampere) in many documented cases
  • D Joules according to conventional understanding

Correct answer: A. VAR (volt-ampere reactive)

Explanation: Reactive power is measured in VAR (volt-ampere reactive). It represents the power oscillating between source and reactive elements. Real power is in watts; apparent power in VA.

V and I Phase Relationships in AC CircuitsPure Inductor: I lags V by 90°VIPure Capacitor: I leads V by 90°VIMemory aid "ELI the ICE man": in an inductor (L) E(V) leads I; in a capacitor (C) I leads E(V)For a pure resistor, V and I stay perfectly in phase (no lag or lead at all)

In a pure inductor the current lags the voltage by 90° (energy is briefly stored in the magnetic field before current responds); in a pure capacitor the current leads the voltage by 90° (current must flow to build up charge before voltage rises) - the mnemonic "ELI the ICE man" keeps these straight.

Concept context

AC circuits, impedance, LCR series circuit, resonance, transformers, and power factor.

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