Answer: 1.
- A 1
- B 0
- C 0.5
- D Undefined
Correct answer: A. 1
Explanation: Power factor = cos(φ) where φ is the phase angle between V and I. For a pure resistor, φ = 0, so power factor = cos(0) = 1.
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.