Re: What is Q?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Herwig Roscher by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>
> 
> Corey May wrote:
> 
> > Hi, I was wondering what is the Q or Q factor is...whatever it is
> > called?
> 
> Corey,
> 
> Q or Quality factor by definition is: reactance divided by loss. For
> coils this means:
> 
>                                 Q = 2 * pi * f * L / loss
> 
> For "loss" you need to use the AC resistance which will be higher
> than the DC resistance (maybe 3 or 4 times higher) due to skin
> and proximity effects.
> 
> Regards,
> 
> Herwig

	In this expression substitute resistance for "loss".  For a SERIES
circuit Q = 2 * pi * f * L / (effective series resistance).  For a
PARALLEL circuit Q = (effective parallel resistance)/(2 * pi * f * L). 
(These equations apply for Q > ~ 10.)

	A more general expression (or definition) of Q:

	Q = 2 * pi * (energy stored)/(energy dissipated per cycle)

Ed