In a parallel-resonant circuit at resonance, the circuit has:

At resonance in a parallel LC circuit, the inductive reactance and capacitive reactance are equal. This creates a high circulating current between the capacitor and inductor within the tank circuit itself. Because this circulating energy sustains itself, very little current is drawn from the external power source at the resonant frequency. When a circuit draws minimal current for a given applied voltage, it indicates a high level of opposition to current flow. As a result, a parallel-resonant circuit presents a very high impedance (maximum opposition) to the source at its resonant frequency.