The impedance of a resonant circuit reaches its minimum at the resonant frequency.

When an alternating current (AC) voltage is applied to a resonant circuit, the impedance of the circuit changes with frequency. At the resonant frequency, the impedance is at its lowest value, which corresponds to the resistance of the circuit. This occurs because, at resonance, the reactive components—inductance and capacitance—effectively cancel each other out, leaving only the resistive part of the impedance.

For frequencies that are either above or below the resonant frequency, the impedance increases due to the influence of the reactive components. Specifically, at frequencies below resonance, the inductive reactance becomes dominant, leading to an increase in impedance as the frequency decreases. Conversely, at frequencies above resonance, the capacitive reactance takes precedence, causing the impedance to rise with increasing frequency.

The frequency response of a resonant circuit can be illustrated by a resonance curve, which depicts how impedance varies with frequency. This curve features a pronounced peak at the resonant frequency, reflecting the low impedance characteristic of resonance. The width of this peak, referred to as the bandwidth, is influenced by the quality factor (Q) of the circuit. A higher Q value results in a narrower bandwidth and a sharper resonance peak.

In conclusion, the impedance of a resonant circuit is minimized at its resonant frequency, where the reactive components balance each other out, allowing only the resistive component to prevail. The frequency response can be effectively represented by a resonance curve, which highlights the relationship between impedance and frequency.