Re: Toroid Design .

> Original Poster: Jim Lux <jimlux-at-jpl.nasa.gov>
> Tesla List wrote:
> >
> > Original Poster: bertpool-at-ticnet-dot-com
> >
> > Date forwarded:         Sat, 19 Dec 1998 14:00:43 -0700
>   It does not matter whether you fill the inside with balls of
> > aluminum foil or even with Greg Leyhs (see his web site for a good
> > example), they will have no charge on them.  The surrounding electrode
> > effectively shields them.  The Tesla coil does not see anything inside the
> > toroid.  The outside, however is a different matter.  Hemispheres on the
> > surface of a toroid just may increase the effective capacitance (Tesla
> > constructed his largest top this way).
> I think that Tesla was using small hemispheres as a construction aid,
> not because a bumpy surface has higher C. He commented in several places
> that you can construct something of large effective radius (for higher
> voltage before breakdown) by combining things of smaller radius close
> together. Electrostatic field calculations, although tedious for any
> practical system, will confirm this. Some more modern practical
> applications include the construction of huge toroids used for testing
> at the IREC HV research center in Canada, field control rings on EHV
> transmission line terminations, and, of course, Greg Leyh's top load
> made from tubing welded into a sphere.
> >
> > Bert Pool
> --
> Jim Lux                               Jet Propulsion Laboratory

I was under the impression (please correct me if I am in error) that
capacitance was a function of surface area. As a hemisphere has twice the
surface area of a circle of equal radius, the capacitance of a hemisphere is
proportionally greater than the space occupied on the surface of another
object. I am still uncertain as to how Greg's top load can function as a
capacitor with so little surface area, unless it has something to do with the
RF wavelenth being long enough to see the surface as continuous (and that may
well be the merest conjecture on my part.)

Bryan Kaufman