Quality Factor (Q)
Definition
How 'pure' an oscillator is — a high-Q tuning fork rings for ages, while a low-Q car suspension soaks up bumps quickly.
Symbol: ·
Technical definition
Q = 2π × (energy stored)/(energy lost per cycle) = ω₀/Δω. High Q means a sharp resonance peak and slow damping.
Example
A quartz crystal in a watch has Q ≈ 10⁴–10⁶ — it loses a minuscule fraction of its energy per cycle, which is why quartz keeps near-perfect time.
Common confusion
High Q is not always better. A radio tuner wants high Q to select one station; a car shock absorber wants low Q so bumps die out instead of bouncing.