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Re: Confused by a derivation.



Either I can't think or ... If one superposes, one obtains for the field
two times (Q/area) / kappa sub zero (with one + & - Q charges on the plates.

bc


"John S. Denker" wrote:

Bernard Cleyet wrote:
...

Why must one add the fields due to two insulating plates with
two G pb's, (very confortable w/ this) and not in the case of conducting
plates.

Huh?

Method 1: You can always add the fields. Always always always.
Linearity and superposability of the fields is one of
their most fundamental properties.
Then you can dot the net field on the unit outward
normal and apply Gauss's law.

Method 2: You can apply Gauss's law separately to
the various contributions to the field, and then
add up the results.

=======

Methods 1 and 2 are equivalent. Superposing the fields
is a linear operation. Applying Gauss's law is a linear
operation.

As my friend Yann once said:
"They're linear. I suspect they commute."

(He said that after walking in on a heated argument as
to which of two operators should be applied first.)