Answer: 50.3 Hz.
- A 50.3 Hz
- B 100 Hz
- C 159 Hz
- D 25 Hz
Correct answer: A. 50.3 Hz
Explanation: f<sub>0</sub> = 1/(2π√(LC)) = 1/(2π√(0.04 × 250×10⁻⁶)) = 1/(2π√(10⁻⁵)) = 1/(2π × 3.162×10⁻³) ≈ 1/(0.01987) ≈ 50.3 Hz.
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.