Re: electrostatic shielding

[Leigh Palmer <palmer@SFU.CA>]

>  > >The sharpness of the disk edges will probably play a
> >  >very significant role in the S(r) distribution.
> >
> >  I think that is not the case if the disc is thin (thickness t
> >  of disc is much less than the radius R).
>
> Intuitively I would expect the opposite. For a thinner disk
> more of the total Q will be near the edge. I am assuming
> that the edge is a circle (radius=0.5*thickness). For a very
> thin disk the E near the edges will result in a corona flow,
> like from a needle. Is this wrong?

My intuition tells me this is wrong. If one makes the disk
progressively thinner, one is, in a sense, getting progessively
farther from the center. There is a finite limit to the charge
that can be, um, marginalized.

My answer to Fred's question is all done intuitively. I don't
know how to calculate this in closed form, but my intuition
for electrostatics is pretty good, and of course I could solve
the problem numerically if I had to. I also have the feeling
that a good mathematical physicist could produce the analytical
solution for the case of a disc of infinitessimal thickness and
verify my intuition. An infinite series approach might work,
but it would be sufficiently ugly that it would likely not
inform my intuition.

Leigh