Question 6A110

In a parallel RLC circuit, at resonance, the inductive reactance ($X_L$) is equal in magnitude to the capacitive reactance ($X_C$). In this specific problem, there is no resistance, so we're dealing with an ideal parallel LC circuit. At parallel resonance, the current flowing through the inductor is 180 degrees out of phase with the current flowing through the capacitor. Since $X_L = X_C$, these currents are equal in magnitude and perfectly cancel each other out. From the perspective of the source, no net current flows into the parallel LC combination. According to Ohm's Law ($Z = V/I$), if current ($I$) approaches zero while voltage ($V$) is present, the impedance ($Z$) approaches infinity. Therefore, the equivalent impedance of this ideal parallel resonant circuit is infinite. Zero impedance would occur in a *series* LC circuit at resonance, where the reactances also cancel, but result in a short circuit. "Median" is not a relevant electrical term for impedance.