Answer: Q 0 /√(LC).
- A Q<sub>0</sub>/√(LC)
- B Q<sub>0</sub> √(LC)
- C Q<sub>0</sub>/LC
- D Q<sub>0</sub> LC
Correct answer: A. Q<sub>0</sub>/√(LC)
Explanation: Energy conservation: Q<sub>0</sub>²/(2C) = (1/2)LI_max². I<sub>max</sub> = Q<sub>0</sub>/√(LC) = Q<sub>0</sub> ω_0 where ω_0 = 1/√(LC).
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.