Re: Capacitor Charged, Right term

["Bob Sciamanda" <trebor@velocity.net>]

The problem of the field lines of a single charged sphere is no different
than the problem of a point charge and its field.  Here we have no trouble
conceiving and using the model of a point charge far removed (isolated) from
all else (a single charge universe).  In both ideal models, symmetry alone
forces radial field lines.

A problem only arises when you try to force the narrow two-element notion of
capacitance upon the isolated charged sphere.  Pioneers in the field have
spoken of the capacitance of an isolated sphere since "time immemorial".
There is clearly no physics problem here, the problem is purely language.

BTW,  If you're going to treat a single charged sphere, you must either
model it as isolated, with field lines extending to infinity, or you must
describe the environment.  In a practical experimental embodiment, "field
lines extending to infinity" applies as an approximation to the real
situation only in the "vicinity" of the charge!

-Bob

Bob Sciamanda   sciamanda@edinboro.edu
Dept of Physics   trebor@velocity.net
Edinboro Univ of PA  http://www.edinboro.edu/~sciamanda/home.html
Edinboro, PA   (814)838-7185

-----Original Message-----
From: Rauber, Joel Phys <RAUBERJ@mg.sdstate.edu>
To: phys-l@atlantis.uwf.edu <phys-l@atlantis.uwf.edu>
Date: Sunday, February 15, 1998 11:21 PM
Subject: Re: Capacitor Charged, Right term


> > To speak of the capacitance of a single sphere is misleading. It is the
> > capacitance of that sphere in combination with the infinite radius "sphere
> > at infinity". If the small sphere has charge Q the sphere at infinity has
> > charge -Q. After all, the radial field originating on Q must continue to
> > -Q.
>
> Ludwik,
> mentioned this situation; and I brought it up and mention it for its
> relevance to the capacitor discussion and for its own right.
>
> I have never been happy with the statement that the field lines on the +Q
> charge must continue to -Q's at infinity.   Why?  Does this mean a universe
> that consists of one positive electron is impossible??
>
> If one insists that a capacitance is two conductors and the charge is
always
> just seperated charge, how did you charge up that single conducting
sphere??
> No doubt with an infinitely long wire hooked to the battery.
>
> My opinion, is that saying that this single conductor capacitor implies
> negative charges at infinity; is simpy a mental construct made solely to
> allow one the mental convenience of saying all field lines orginate on
> positive charges and terminate on negative charges; *always*.  I don't
think
> it is necesary to say this nor even correct; Because I think a universe of
> one proton only is consistant with Maxwell's equations, and would be a
> universe with no negative charges upon which the Field lines from the
proton
> would terminate.
>
> I admit, I'm venturing into the realm of meta-physics to some extent, but
> thoughts and opinions are welcome
>
> Joel