Answer: V/R (maximum possible current).
- A V/R (maximum possible current)
- B V/Z (with Z minimum at resonance)
- C 0
- D V/(X<sub>L</sub> + X<sub>C</sub>)
Correct answer: A. V/R (maximum possible current)
Explanation: At resonance, Z = R (minimum). I = V/Z = V/R. This is the maximum possible current in the circuit. Both options A and B state the same thing at resonance.
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.