Answer: 250 W.
- A 250 W
- B 500 W
- C 1000 W
- D 750 W
Correct answer: A. 250 W
Explanation: P<sub>avg</sub> = (V<sub>0</sub> I<sub>0</sub>/2) cos(φ) = (100 × 10/2) × cos(π/3) = 500 × 0.5 = 250 W.
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.