Re: batteries (again)

[Joseph Bellina <jbellina@SAINTMARYS.EDU>]

On Tue, 5 Mar 2002, Justin Parke wrote:

> Another set of questions about batteries:
>
> Does an electric field always exist between the terminals of a battery?
Yes, if it did not, then there would no ion current to complete the closed
circuit of current flow (electrons in the conductor and ions in the
electolyte of 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?

The electric field created by the battery and the induced charges on the
conductor surface exist everywhere...your question hints at the notion of
shielding, that the field is prevented from being somewhere by some
object or objects.  There is no such shielding, just the superposition of
the fields due to the various charges that exist.

> 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?
The presence of a static electric field does not imply the existence of a
current.  SInce the air is not a conductor, the only way to get conduction
is to create ions and electrons...cosmic rays will do that in small
numbers.  If the field is very large then the electrons released by such
cosmic event might gain enough KE before colliding with a molecule so that
the collision could ionize the molecule.  That process could continue and
produce a spark, or set of sparks...but the field would have to be very
high...not the sort of thing you would get with a battery.  Or if you did
get it with an ensemble of batteries, would be such a person killing
device that one would not what to have it around.

cheers,

joe

> > Thanks > > Justin Parke >

Joseph J. Bellina, Jr.               219-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556