Answer: 0.316 A.
- A 0.316 A
- B 0.224 A
- C 0.158 A
- D 0.500 A
Correct answer: A. 0.316 A
Explanation: Initially all energy is in the capacitor: U = (1/2)CV<sup>2</sup>. At maximum current, U = (1/2)LI<sub>max</sub><sup>2</sup>. Thus I<sub>max</sub> = V√(C/L) = 20√(50×10<sup>-6</sup>/0.2) = 0.316 A.
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.