Re: split toroid

From: 	Robert W. Stephens[SMTP:rwstephens-at-headwaters-dot-com]
Sent: 	Sunday, June 22, 1997 9:07 PM
To: 	Tesla List
Subject: 	Re: split toroid
> From: 	Dan Kline[SMTP:ntesla-at-vishnu.csd.sc.edu]
> Sent: 	Thursday, June 19, 1997 9:14 PM
> To: 	tesla-at-pupman-dot-com
> Subject: 	split toroid
> Hi all,
> I have a toroid question:
> I'm making a toroid out of two toroid-halves, sorta, like if one was to cut
> a bagel in half, and I'm putting those two halves together to make a toroid.
> The question is, should I join the two halves around the outside
> perimieter, or should I leave the outside perimeter separated?
> If capacitance is a function of surface area, then not joining the outside
> perimeter would increase the capacitance, wouldn't it?
> In other words, I'd have a toroid with a split all the way around the
> outside edge, with an inside surface and an outside surface, rather than a
> joined perimeter, with only an outside surface.
> I hope that's not too unclear...
> Dan

If you are thinking that by leaving a gap between your toroid halves 
the entire insdide surface will suddenly become available as surface 
area to add to the outside and give nearly double the total 
capacitance, then you are unfortunately wrong.  The inside is completely 
shielded and enclosed by a faraday cage preventing it to function in an 
additive way to the capacitance of the toroid.  You will actually 
measure a fractional increase as you pull the two halves apart, but 
this is due to end effect, where up to a certain point, the distance 
you've pulled the toroid halves apart, will electrically look like 
they are still a solid metal sheet.