Re: Non-conservative forces in a liquid dielectric

[Pentcho Valev <pvalev@BAS.BG>]

Bob Sciamanda wrote:

> Panofsky & Phillips raised the question (rhetorically) and answered it.  Their
> contention is that the reduced force is not accounted for by the explicit
> Coulomb forces alone - the increase in hydrostatic pressure (in the E field
> region) must also be taken into account.

This is not an explanation - rather, the increase in pressure is an empirical fact.
Something similar to explanation could be found on p. 114:

"The physical reason for this is that the energy of dipoles in an electric field is
lower than their energy in field-free space, and therefore the dipoles in the liquid
are drawn into the regions of higher field in order to satisfy the condition that
the potential energy be a minimum."

This explanation is contradictory but since such explanations are part of the
tradition I would not be convincing if I tried to prove my claim. Still two
questions need to be answered. How do you relate this explanation to the dielectric
constant showing how many times the force of attaction between the plates has
decreased (compared to that in vacuum), and then you will have to prove that this
value of the dielectric constant is equal to the value of the dielectric constant
showing how many times the voltage between the plates has decreased. Both dielectric
constants are taught to freshmen so you would agree that utmost clarity is needed.
     The second question concerns the energetics of the process. For some reason
water comes between the plates and even rises high above the surface of the pool. At
the expense of what energy? Again, a freshman who has studied the first law may ask
you this simple question.

Pentcho