Re: Flat conductors (was I need help).

[Bernard Cleyet <anngeorg@PACBELL.NET>]

the beauty of using a brine tank is that it may done "3D", as described on p.
100 (Harnwell).  [The probes and electrode connections must, of course, be
insulated.]


"Why should the gradient be parallel to the paper boundary everywhere, as it
seems to be?  I know why the E lines are
perpendicular to conductive surfaces in electrostatics but I do not know why
should they be parallel to the surface
inside a conductor connected to a battery.
Ludwik Kowalski"

To not be perpendicular would imply (exply?) a current outside or through the
boundaries of the paper.  This happens in the "electrostatic" case where the
paper's resistivity approaches that of the outside medium (air).

I have finally duplicated LK's reduction in the size of the paper to determine
the effect on the equipotentials.  Reducing the depth (Y direction) from 18 cm
to 16 cm made only a noticeable difference on the ~ two cm D. equipot.  i.e. ~
< 5% change from the original V (potential).  A further reduction of 4 cm still
was not measurable in that the movement of the equipotential was less than the
resolution of the probe (slightly dulled push pin).  Earlier I found that gross
change (1/2 cm movement) requires a change in the edge ( one cm) when the edge
is < ~ 4 cm from the nearest point on the equipotential.

All this JM shows.

bc


kowalskil wrote:

> Carl Mungan was describing experiments in a tank last
> year. It would be very interesting to know if a transition
> from the conductive behavior to electrostatic behavior
> could be observed. Are you there Carl? Who else is in a
> position to try to explore Joseph's idea?
>
> I think I will share something very interesting soon. But
> let me do this again first. The Pasco paper offers many
> new experiments. Please start experimenting, if you can.
> Student research projects can be exciting in this area.
>
> Ludwik Kowalski
>
> Joseph Bellina wrote:
>
> > The original experiments, I think, of this sort were not done with
> > resistive paper but with flat tanks of conducting solutions in which metal
> > objects were placed.  I wonder if any of the issues you have been
> > discussing could be probed by looking at the patterns as a function of the
> > conductivity of the liquid.  If the conductivity is high, is seems to me
> > that the patterns would be dominated by conduction effects, as they are on
> > paper.  Whereas is the conductivity was very low, you might expect to see
> > something that looks more electrostatic...or so it would seem.
> >
> > what do you'all think?
> >
> > joe
> >
> > Joseph J. Bellina, Jr.               219-284-4662
> > Associate Professor of Physics
> > Saint Mary's College
> > Notre Dame, IN 46556