Answer: XL = XC (inductive reactance equals capacitive reactance).
- A XL = XC (inductive reactance equals capacitive reactance)
- B R = XL, when resistance equals inductive reactance
- C R = XC, when resistance equals capacitive reactance
- D Z = 0, when the total impedance vanishes entirely
Correct answer: A. XL = XC (inductive reactance equals capacitive reactance)
Explanation: At resonance, XL = XC, so the reactances cancel. Z = R (minimum), current is maximum. Resonant frequency 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.