Re: batteries (again)

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

----- Original Message -----
From: "Justin Parke" <FIZIX29@AOL.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, 05 March, 2002 09:51
Subject: batteries (again)


> Another set of questions about batteries:
>
> Does an electric field always exist between the terminals of a battery?

Answer: As long as the terminals are at different potentials (the battery is
not completely discharged), an electric field will exist between them. The
field lines are both inside and outside the battery.

> When a conductor is placed in contact with the terminals of a battery, is
the electric field constrained to exist only within the conductor?

Answer: 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).
The field between terminals in question 1 is then modified by the presence
of the conductor.

> If there is an electric field that exists outside the conductor near the
terminals of a battery, is there a flow of charge (say ions in the air) in
that region, and if so, is it measurable?

Answer: There is, indeed, a field outside the conductor. It fills the region
between the terminals. If the substance between the terminals contains
charge carriers (free electrons or free ions), there is a current. If there
is no substance (a vacuum), there is no current. Since dry air always
contains at least a few charge carriers, there will be a small current
(probably too small to be measured. The air on a seashore will contain more
charge carriers (sodium ions, chlorine ions), so the current is greater
there.

> Thanks
>
> Justin Parke