Re: Self capacitance and Medhurst

To: tesla-at-poodle.pupman-dot-com
Subject: Re: Self capacitance and Medhurst
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 26 Mar 1997 23:11:23 -0600
Approved: tesla-at-stic-dot-net

Subject: 
        Re: Self capacitance and Medhurst
  Date: 
        Wed, 26 Mar 1997 17:35:01 -0800 (PST)
  From: 
        "Edward V. Phillips" <ed-at-alumni.caltech.edu>
    To: 
        tesla-at-pupman-dot-com


Re:
"> Capacitance is mostly dependent on the dielectric and area. For a
coil self
>capacitance this would relate to the wire insulation and wire length.  The
>Medhurst equation uses only radius and coil length for the coil self
>capacity. As Steve points out this can lead to some wild results."
        As noted before, I also disagree.  First of all, the capacitance
is almost independent of the dielectric on the wires and the dielectric
(constant) of the form.  Make that self capacitance.  I've gotten
results
as close or closer than Mark reports.  As for Wheeler's formula, which
is intended to be a "working formula", I've found that it when I get
results which are in error by several percent it is usually because
I didn't count the turns correctly.  I have other formulae for
inductance
and mutual inductance which are supposed to be good to within 0.1%,
which is closer than one can usually measure any of the physical
parameters of the coil.  For Tesla coil work they aren't worth
the bother.
Ed Phillips