Q.Define quality factor.

The quality factor $Q$ measures the sharpness of resonance of a series LCR circuit; $Q=\dfrac{\omega_0 L}{R}=\dfrac{1}{R}\sqrt{\dfrac{L}{C}}$.

Definition: In a series LCR resonant circuit, the quality factor is defined as the ratio of the voltage developed across the inductor (or capacitor) at resonance to the voltage across the resistor, or equivalently as $2\pi$ times the ratio of the maximum energy stored in the circuit to the energy dissipated per cycle. A high $Q$ means a sharp, narrow resonance curve (a highly selective circuit); a low $Q$ means a broad, flat resonance curve.

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