# RE: K Factor & Mutual Inductance

```Subject:
RE: K Factor & Mutual Inductance
Date:
Thu, 10 Apr 1997 07:54:36 -0400
From:
Heinz Wahl <hwahl-at-jtc-campus.moric-dot-org>
To:
"'Tesla List'" <tesla-at-pupman-dot-com>

John,

You state that the R is effective, not DC or AC. Why can't you
measure the R of the coil, calculate the XL, at the
expected frequency of operation, and use the result to find a ballpark
Q? Could you elaborate on effective R?

Heinz

>
>
>Hi John, All,
>Have you ever tried the formula Q = sqrt( L / C ) / R.
>
>Barry
>
> ----------------------------------------------------

Barry -

I have never seen the above Q factor equation before. What would you
use
for R? In the usual equation   Q = X/R   where X = 6.283 F L  the R is
an
effective resistance, not DC or AC.  The only way to find the R is to
use a
value for a typical Q and X and solve the equation for R. The Q factor
like
the K factor is easily found by tests after the TC is built, however, at
the
design stage these two factors are difficult to determine.

The basic nature of Q for Tesla coils has to do with the energy stored
in
the field of the coil and the energy dissipated. The Q factor also
involves
resonant rise in voltage and other electrical effects. It is also
interesting that Q involves other phenonmena such as in the swing of a
pendulum and in horological science ( measuring time).

John Couture

```