The voltages across the inductor and capacitor in a circuit at resonance are substantially opposite in phase (the loss resistances affect the phasing slightly) and cancel each other. The voltage developed across the inductor, usually the lossiest component, compared with the voltage applied in series to the circuit, is a measure of the ‘goodness’ of the circuit. This ratio is often referred to as the magnification factor, Q, of the circuit. The Q factor is calculated from:
ωL or 1Q= R ωCRwhere L and C are in henries and farads respectively.