Answer: f = 1/(2π√(LC)).
- A f = 1/(2π√(LC))
- B f = 2π√(LC)
- C f = 1/√(LC)
- D f = RC/L
Correct answer: A. f = 1/(2π√(LC))
Explanation: In an ideal LC circuit (no R), energy oscillates at f<sub>0</sub> = 1/(2π√(LC)). When capacitor is fully charged, I=0. When capacitor is discharged, all energy is in inductor.
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.