Re: Confused by a derivation.

["John S. Denker" <jsd@MONMOUTH.COM>]

"RAUBER, JOEL" wrote:
>
...
> When you think in these terms, you find that conductors don't such much
> provide impenetrable barriers to E field, but rather provide a source of
> non-zero charge density that provides electric field that superposes in a
> "destructive" way with that of the sources (from which you are presumably
> shielding regions of space, e.g. with a Faraday cage).

I'm glad Joel agrees with me.
And I still agree with what I wrote.

But let me say that the point of view Michael E.
advocated is not really wrong;  it's just a
different point of view.

In particular, if I underderstand where M.E. is going,
it winds up expressing the Maxwell equations in
terms of E and D and B and H, with a constituative
equation connected D to E, and another connecting
H to B.  This is not wrong.  Some people consider
it slightly old-fashioned.  It simplifies certain
problems, but it complexifies certain others.
Whenever I get confused, I run home to the E and B
formulation (no D and no H) which is the way I was
taught.  I recommend the E and B (only) approach,
especially for intro courses, but your mileage
may vary.