Re: batteries (again)

["Paul O. Johnson" <pojhome@SWBELL.NET>]

----- Original Message -----
From: "kowalskil" <kowalskil@MAIL.MONTCLAIR.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, 05 March, 2002 16:25
Subject: Re: batteries (again)


> Justin Parke asked:
>
> > > ...When a conductor is placed in contact with the terminals
> > >    of a battery, is the electric field constrained to exist only
> > >    within the conductor? ...
>
> Paul  Johnson answered the question:
>
> > If the conductor is in contact with only one terminal, the situation
> > is static (no current flows). In such a static case, the field inside
any
> > conductor is zero (all points in the conductor are at the same
potential).
> > potential). The field between terminals in question 1 is then modified
> > by the presence of the conductor.
>
> I think that Justin's question was about a long wire connected to
> the battery terminals. How does the distribution of electric field
> lines (and equipotential surfaces) is changed (in comparison with
> what it was when the wire was disconnected and was far away.)
> This question has not been answered.

By George, you're right, Ludwik. I completely overlooked the "s" at the end
of "terminal". I thought he was describing a conductor of undefined shape
connected to only one terminal. That's what my answer applied to.

If a wire is connected between the terminals, the situation is obviously no
longer static. A potential gradient exists along the wire and field lines
run along the gradient pushing free electrons uphill. They constitute the
current that flows.

Field lines also exist outside the wire. They bulge out from the wire's
surface, their spacing indicating decreasing field strength with increasing
radial distance from the wire. They go from points of higher potential on
the wire (nearer the positive battery terminal) to points of lower potential
(nearer the negative terminal). The field lines display cylindrical symmetry
around the axial wire.

poj