Re: Confused by a derivation.

["RAUBER, JOEL" <JOEL_RAUBER@SDSTATE.EDU>]

> "RAUBER, JOEL" wrote:
> ...
> > How do you prove the E field is zero inside an ideal
> conducting material?
>
> For electrodynamics, I don't.
> For electrostatics, see below.
>
> > I do it with Gauss' Law (and the electro-static equilibrium
> assumption).
>
> I do it with no Gauss's Law at all:

I beat you to the punch and rescinded my comment after reading Bob's
objection (the same as yours).  :-)

> > This tells me that in some fashion Gauss' Law is sufficient
> for deducing
> > zero field in the conductor and hence the rest of the arguement.
>
> Not quite.
>
> You need at least:
>  -- definition of conductor
>     (You can't prove anything about conductors without
>      invoking the definition of conductor!)
>  -- definition of "static" as in "electrostatic"
>  -- Coulomb force law.
>     (It doesn't help to know the fields if you
>      don't know how charges respond thereto.)
>  -- Gauss's law, or some other way to work out the fields.

The need for these definitions is why I carefully wrote in the words "in
some fashion", of course, its moot for reasons pertaining to your first
objection!

Joel R