# Re: Toroid Design .

```
>
> 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.)

Capacitance is a function of surface area, IF (and only IF), there isn't
any overlap of the fields from the surfaces. In any real system, there is
such an overlap. In a tube frame, or Telsa's Wardenclyffe set up, or Greg
Leyh's Electrum, etc., the conductors are close enough to each other that
the net field from all the components is actually pretty smooth.

Fortunately, there aren't any nonlinearities, so you can just add up the
field at each point from each component. This is called superposition. Of
such calculations are finite element electrostatic computations made. You
break your thing up into tiny little pieces, calculate the field for each
piece, and add them up. Then, to get the total capacitance, you integrate
the field over some convenient surface.

Your comment about RF wavelength is also well taken. Essentially, the same
rules apply with RF structures (superposition), but, if the structure is a
significant fraction of a wavelength (say more than a tenth), then it isn't
all at the same potential at the same time, so the calculations get more
complex (it isn't "statics" any more). At this point, you now have an