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Quality factor
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Number of radians over which energy decays by 1/e.
Q = ω₀m/bQ = ω₀m/b measures how weakly an oscillator is damped: it's about 2π times the energy stored over energy lost per cycle. High Q means sharp resonance and long ringing.
A tuning fork has Q of a few thousand.
Q has no unit.
In more detail
The quality factor Q measures how little damping an oscillator has, roughly the number of oscillations before the amplitude falls significantly. High Q means sharp resonance and low damping.
Real-world uses
- Quartz crystal oscillators in watches have very high Q for stable timing.
- Radio filters use high-Q circuits to select narrow frequency bands.
- Physicists describe the quality of a resonator, such as a guitar string or a microwave cavity, using its Q factor.
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Frequently asked questions
Is high Q always good?
It depends. High Q gives sharp, precise tuning, but the response is narrow and sensitive.
How is Q defined?
As 2π times the energy stored divided by the energy lost per cycle.
What does a high Q mean?
A high Q means the oscillation loses energy slowly, so the resonance is sharp and the oscillation lasts a long time.
Related topics in Oscillations & SHM
Differential equation of SHM · Damped oscillations · Underdamped, critical, overdamped · Forced oscillations · Resonance · Resonance examples