Answer: 45° (lagging).
- A 45° (lagging)
- B 45° (leading)
- C 0°
- D 90°
Correct answer: A. 45° (lagging)
Explanation: tan(φ) = (X<sub>L</sub> - X<sub>C</sub>)/R = (20-10)/10 = 1. φ = 45°. Since X<sub>L</sub> > X<sub>C</sub>, the circuit is inductive and I lags V (lagging power factor).
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.