RE: Top Capacitance Dominant?

To: tesla-at-pupman-dot-com
Subject: RE: Top Capacitance Dominant?
From: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Mon, 01 May 2000 16:34:20 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi John,

> Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net> 
> 
> 
> Terry -
> 
> Another possibility is that the toroid loses capacity when it is mounted on
> the secondary coil. This would mean the coil self capacity is more than 3
> pf. In an earlier post I said the toroid looses 15 to 20 % of its free space
> capacity when placed on the secondary.

That depends on the relative size of the terminal and secondary. If 
the secondary diameter is substantially greater than the toroid 
diameter, the total capacitance hardly changes from that of the bare 
coil. Just in case the TX line afficianados take issue with what really 
is capacitance, I should have said that the resonant frequency 
hardly changes. Been there - done that.
 
> A few years ago I read somewhere that a typical single wound TC coil would
> lose most of its self capacitance if the windings were spaced more than 31
> mils apart. Could this be one of the reasons why Tesla built the CS coil
> with about 3 inch spacing? The Medhurst equation does not even use windings!

It will lose inter-turn capacitance but not sheet capacitance (as Tesla 
discovered to his utter despair during his time at Colorado Springs).

In the mode in which the coil is used (yes - it really does matter) 
interturn capacitance appears to have negligible influence on 
function. Reasonably so if you consider that each turn-turn C is in 
series and each turn is shielded from all but its immediate 
neighbours (except for a relatively vast distance when turns are 
staring at each other from opposite sides of the coilform).

Regards,
malcolm