RE: New Inductance Formula

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

Original poster: "Jan Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>

(Terry is probably killing this thread soon... hope I can slip my $0.02
through before that... ;o)

Hi Dave,

> In the MKS system the equivalent expression would be 
> 	L = weber/amp

That is a no-no. Ok, Henry is equal to weber/amp, whereas "L" is certainly 
not, as it is not a unit. Formulas, constants and units are different
things, although many people somehow don't realize this. 
Mainly, see

 http://physics.nist.gov/Pubs/SP811/sec07.html  
 part 7.11 & 7.14
 (Dave, for your scientific publication, you should really keep to the
  rules given there... that is, if you want to keep within SI)

The Wheeler "formula" is a function like k=f(x,y,z), attempting to fit  
an experimentally determined curve, and in itself is unitless. You may say
"L_tc_sec  = f(x,y,z) mH/m" in order to interpret the result as
inductance, and as a bonus have your unit relations working as well.
"Reverse engineering" f(x,y,z) it is futile...

Anyway, a much more valid approach than fiddling around with the Wheeler
function is

  http://www.abelian.demon.co.uk/tssp/
  http://www.abelian.demon.co.uk/tssp/pn2511.html

because, unlike the Wheeler formula/function, this is an actual (attempt
at a ;) derivation. The messy finite element analysis thingy is left as an
excercise to the reader. As usual. ;o)

The other way to go is to measure a huge number of different coils and try
to invent a formula that fits the measurement data with as little error as
possible. Not an easy task, this one, either...

cheers,

 - Jan

--
*************************************************
 high voltage at http://www.hut.fi/~jwagner/tesla