Re: Electric field in a grounded conductor

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

"Casuga, Adele" wrote:
> question from "Physics" by
> Eugene Hecht 1994 (p. 619 # 3)
>
> "Figure Q3 shows a dipole in a room (which is represented by a large
> grounded conductor). Make a rough sketch of its E-field and explain your
> reasoning."
...
> Outside the box, there shouldn't be any field.

True, by the usual screening theorems.

> I would reason that the electric field inside the box would behave as if the
> box weren't there.

Not true.  No reason why it should be true.  Can't be true.
There must be induced charges on the walls.
If the box "weren't there" the dipole would produce a
nonzero field everywhere, and when the box is there
it must be an equipotential.

The conventional way to solve such problems is to
impose periodic boundary conditions.  This is a
special case of the "method of images".

A spreadsheet to help you visualize such things is
available at

  http://www.monmouth.com/~jsd/physics/laplace.html