Capacitance of a cylinder coil

From:  Antonio C. M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
Sent:  Thursday, April 09, 1998 12:54 AM
To:  Tesla List
Subject:  Re: Capacitance of a cylinder coil

Jim Lux wrote:

> > C=11.26*length+16*radius+76.4*radius^(3/2)/length^(1/2) pF

> I note that this tracks pretty well ( a few percent) with the tabular
> Medhurst, as provided by Rzeszotarski in an earlier post (and manifested on
> my web page). Does the original reference provide any bounds for where the
> formula is valid? Do you have an actual reference for this (i.e. is it the
> same "Wireless Engineer" papers, etc.)?

I found the formula in the paper "A high potential Tesla coil impulse generator
for lecture demonstrations and science exhibitions"," by Skeldon, Grant, and Scott,
American Journal of Physics, 68 (8), August 1997, pages 744-754. There is no
comment there about validity bounds. The original reference is "H. F. resistance
and self-capacitance of single-layer solenoids, by R. G. Medhurst, Wireless Eng.
21, 80-92 (1947).

I couldn't find the original paper here. Do someone have a copy that can send me?

I tested the formula with some coils that I have (several RF, one Tesla resonator),
and it appears to work quite well.
Antonio Carlos M. de Queiroz