Re: mapping out equipotentials

[John Denker <jsd@MONMOUTH.COM>]

At 09:40 AM 2/2/01 -0500, Carl E. Mungan wrote:
> This does not however imply that the electric field outside the water
> is zero. Outside the water we have both J=0 and sigma=0, so Ohm's law
> can't tell us anything about E.

Right.

As David Bowman pointed out, you don't have a ghost of a chance of
measuring the E-field in the air using an ordinary voltmeter.  OTOH it is
amusing to keep in mind that there do exist very-high-impedance instruments
for measuring the such fields.  For starters
  http://www.google.com/search?q=electrostatic+field+mill
and in particular
  http://www.colutron.com/download_files/chap6.pdf

> I don't see any reason that [the tangential] component of E should be much
> weaker just outside the water than inside.

I agree.  Indeed I rather suspect that this component is _exactly_ the same
just outside and just inside the surface.  Prof. Maxwell had something to
say about curl E.