Answer: 800 W.
- A 800 W
- B 200 W
- C 1000 W
- D 1250 W
Correct answer: A. 800 W
Explanation: Efficiency = P<sub>out</sub>/P<sub>in</sub>. P<sub>out</sub> = 0.80 × 1000 = 800 W. 200 W is lost as heat in the core and windings.
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.