RE: K Factor & Mutual Inductance

            RE: K Factor & Mutual Inductance
            Mon, 14 Apr 1997 08:28:36 +1200
            "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
            Wellington Polytechnic, NZ

John, all,

>  Thank you for the derivation of Q = sqrt(L/C)/R.  I lost my Radiotron
> years
> ago (a good book). I did find the derivation in Henney's Radio
> Engineering
> Handbook.
> The sqrt(L/C) is shown in my TC Notebook to calculate the secondary
> circuit
> peak current. This is the equivalent of Zo in Ohms law. The Zo and Xo
> are
> consudered almost equal for these calculations.
> Apparently we both agree that the R is not the DC or AC resistance. It
> must
> be determined by calcs after finding the Q and the X of the coil.

Whoa! It is the resistance at the frequency of interest (effective 
AC resistance). The rho of the material is factored in. The only 
reason it is difficult to calculate is the many-bodied problem. The 
surroundings affect it. You can test this for yourself. Try mounting 
a primary and cap close to ground and measure its Q without the gap. 
Then sit it up a few feet and measure again. This should be of 
interest to anybody wanting to couple more primary power to the 
secondary than ground etc.  You can also see the effect of doing this 
on the secondary.