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Re: Why does electrostatic attraction in water decrease?



Some additional remarks:

1) I haven't seen the exact phrasing of Panofsky's
example. Conflicting versions have been posted.

2) I can nevertheless guess and probably come
pretty close to fingering the underlying physics.
There are a zillion problems of this sort, all
rather similar.

a) You can figure out what the answer is pretty easily
using energy considerations.

b) When people start asking about details of the
mechanism, all the details reside in the fringing
fields.

In this case, to see the role of fringing fields,
punch a small hole right in the middle of one of the
capacitor plates. Does the high-pressure water
between the plates leak out through the hole? No.
Why not? Huge field gradient at the location of
the hole.

For other geometries (e.g. at the ends of the plates,
as opposed to at the hole) it's laborious to track
down the details of the field gradients. Laborious
and unenlightening. It doesn't tell you anything
of interest beyond what the energy principle told
you.