Re: Non-conservative forces in a liquid dielectric

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

On Wednesday, May 14, 2003 3:49 AM, Pentcho Valev wrote:

> [snip]
> When two opposite
> charges (e.g. the plates of a capacitor) are immersed in 
> water, why does the force of
> attraction between them decreases 80 times?

I'd like to consider a different situation.  Suppose we have a
parallel-plate capacitor, separated by a vacuum, with plate
separation D and capacitance C.

 -Q|      |+Q
---|      |---
   |      |

What happens if we insert into the vacuum a piece of
something as follows:

 -Q| |  | |+Q
---| |--| |---
   | |  | |

such that we now have two capacitors in series, each with
plate separation D/3?

Does the force of attraction between the -Q and +Q change?
If so, in what way?

Does the capacitance increase to 1.5 what it was before?
Is this equivalent to a "dielectric constant" of 1.5?

> [snip]
> If we 
> imagine an analogous
> situation in which all participants are macroscopic (e.g. a 
> capacitor plus some
> macroscopic "dipoles" between the plates able to rotate and 
> "polarize") we see that
> polarization, per se, must increase rather than decrease the 
> attraction. In other words,
> electrical forces can by no means be held uniquely 
> responsible for the effect.

In my case, if we imagine that the charges within my "insert"
separate so that we have

    +Q  -Q
 -Q| |  | |+Q
---| |--| |---
   | |  | |

we see that the "polarization" of the insert must increase
the attraction rather than decrease the attraction.

Does this mean that electrical forces can by no means be held
uniquely responsible for the effect?

What am I missing?
____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; 570-422-3428; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ., E. Stroudsburg, PA 18301