Q is for .... Q factor

Q is for .... Q factor

New postby Fortunat Mueller-Maerki » Thu Oct 02, 2008 3:41 pm

Q factor

(With input from Wikipedia, the free encyclopedia)

The q factor is a concept used in oscillation science (a sub part) of physics that measures the quality of an osciallator. As most timekeepers have at their heart some sort of an oscillator (a pendulum, a balance wheel, a foliot, a quartz etc) the q - factor is an important concept for horological sciencits, the people who study the theory and concept behind watches and clocks.

"In physics and engineering the quality factor or Q factor is a dimensionless parameter that compares the time constant for decay of an oscillating physical system's amplitude to its oscillation period. Equivalently, it compares the frequency at which a system oscillates to the rate at which it dissipates its energy. A higher Q indicates a lower rate of energy dissipation relative to the oscillation frequency, so the oscillations die out more slowly. For example, a pendulum suspended from a high-quality bearing, oscillating in air, would have a high Q, while a pendulum immersed in oil would have a low one. The concept originated in electronic engineering, as a measure of the 'quality' desired in a good tuned circuit or other resonator.

Generally Q is defined to be

Q = ω times [ (Energy Stored) /(Power Loss) ] ,

or, more intuitively,

Q = 2 π times [ {Energy Stored) / (Energy dissipated per cyclel) ]

where ω is defined to be the angular frequency of the circuit (system), and the energy stored and power loss are properties of a system under consideration."

In simplified terms, for a pendulum, Q measures how long a no longer impulsed pendulum takes to 'decay' to half its swing. A 'better' pendulum, e.g.with less air resistance and a better pendulum suspension, or a pendulum with a higher mass, takes longer to decay.

Fortunat Mueller-Maerki
Sussex NJ USA

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