Quality Factor
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Quality Factor
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A measure of the sharpness of resonance or
frequency selectivity of a resonant vibratory system having a
single degree of freedom, either mechanical or electrical. See vibration.
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In a mechanical system, this quantity is very nearly equal to one-half
the reciprocal of the damping ratio. When used with reference to a lightly
damped system, it is also approximately equal to the following: (1)
transmissibility at resonance; (2) π/δ where δ is the logarithmic decrement; (3)
2πW/ΔW where W is the stored energy and ΔW the energy dissipation per cycle; and (4)
fr/Δf where fr is the resonance frequency and Δf is the bandwidth between the half-power points.
Historically the letter Q was an arbitrarily chosen symbol to designate the
ratio of reactance to resistance of a circuit element. The name quality factor
was introduced later.
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References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use