Answer: Vrms = V 0 /sqrt(2).
- A Vrms = V<sub>0</sub>
- B Vrms = V<sub>0</sub>/sqrt(2)
- C Vrms = V<sub>0</sub> x sqrt(2)
- D Vrms = V<sub>0</sub>/2
Correct answer: B. Vrms = V<sub>0</sub>/sqrt(2)
Explanation: Vrms = V<sub>0</sub>/sqrt(2) = 0.707 V<sub>0</sub>. For household 220 V AC, peak voltage = 220 x sqrt(2) = 311 V.
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.