Physics > Alternating Current > 4.0 Circuit element in AC circuit
Alternating Current
1.0 Introduction
2.0 Alternating current and alternating voltage
2.1 Instantaneous current and voltage
2.2 Mean or average current and voltage
2.3 Root mean square current and voltage
2.4 Form factor
3.0 Some important terms
4.0 Circuit element in AC circuit
4.1 Pure resistor circuit
4.2 Pure inductor circuit
4.3 Pure capacitor circuit
4.4 Series $L-R$ circuit
4.5 Series $C-R$ circuit
4.6 Series $L-C-R$ circuit
4.7 Resonance series $L-C-R$ circuit
4.8 Quality factor
4.9 Summary
5.0 Power in AC circuit
4.8 Quality factor
2.2 Mean or average current and voltage
2.3 Root mean square current and voltage
2.4 Form factor
4.2 Pure inductor circuit
4.3 Pure capacitor circuit
4.4 Series $L-R$ circuit
4.5 Series $C-R$ circuit
4.6 Series $L-C-R$ circuit
4.7 Resonance series $L-C-R$ circuit
4.8 Quality factor
4.9 Summary
It is a measure of sharpness of resonance. It is defined as the ratio of reactance of either the inductance or capacitance at the resonant angular frequency to the total resistance of the circuit.
$$Q = \frac{{{X_L}}}{R} = \frac{{\omega L}}{R}$$ or $$Q = \frac{{{X_C}}}{R} = \frac{1}{{\omega CR}}$$ $$Q = \frac{1}{R}\sqrt {\frac{L}{C}} $$
Quality factor is also expressed in terms of bandwidth,
$$Q = \frac{{{\text{Resonant frequency}}}}{{{\text{Bandwidth}}}}$$
