Answer: 78.1 V and 39.8.
- A 78.1 V and 39.8°
- B 110 V and 36.9°
- C 170 V and 53.1°
- D 78.1 V and 50.2°
Correct answer: A. 78.1 V and 39.8°
Explanation: The net reactive voltage is 80 - 30 = 50 V. Hence V = √(60<sup>2</sup> + 50<sup>2</sup>) = 78.1 V. Also tan(φ) = 50/60, giving φ = 39.8°.
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.