Re: Current Flow (shouldn't it be "charge flow?")

[William Beaty <billb@ESKIMO.COM>]

On Sat, 20 Apr 2002, Brian McInnes wrote:

> on 20/4/02 7:35 PM, William Beaty at billb@ESKIMO.COM wrote:
>
> > If we constantly talk as if there were a substance called "current" which
> > flows through conductors, won't students come to believe that this
> > substance exists?  Yet the "substance" flowing through wires is not called
> > current, it's called charge.
> I know that we've been here (or in a place very much like it) before BUT is
> charge a substance?

So you believe that an electric current is NOT a flow of electric charge?
(If charge is not a substance, than how could it ever flow?)

:)

We model it as a substance because it, like mass and energy, is a
conserved quantity.  If charge is not substance-like, then an electric
current is not a flow.

But more to the point: should we unwittingly teach students that the
"stuff" which flows along conductors is called "current?"  I constantly
exchange mail with students, technicians, and engineers.  I find that a
significant number of them (perhaps even the majority)  believe that
"current" flows inside of metals.  Most of the non-engineers have never
encountered the phrase "charge flow" at all. I have even encountered many
otherwise intelligent people who strongly object to the description of
electric current as a flow of electric charge, instead they insist that it
is a flow of "electricity."

In my opinion, the phrase "current flow" is the cause of enormous amounts
of misconception.  If we could perform some grammatical engineering and
totally remove the phrase "current flow" from all textbooks, then the
understanding of things electrical would take an enormous leap forward.

> I, for one, don't believe so.  Electrons have the property of mass and
> charge.  Electrons flow through the wire.

Electrons are charge carriers, so when electrons flow, charge flows too.
Charge obviously is not an *independant* substance.  However, unless you
can tell me how to get some charge into the interior of a closed Gaussian
surface without transporting it through that surface, then I'll have to
insist that charge certainly is substance-like, and it certainly can flow
from place to place using a conductor.

Perhaps we should examine our definition of the word "substance."  Suppose
we define "substance" as:

  "a conserved entity, an entity which must be transported through a
   closed surface in order to enter or leave the interior."

Under this definition, charge is MORE like a substance than, say, water.
After all, water is only sometimes conserved, and it can be created and
destroyed (by burning H2 and O2, or by electrolysis, respectively.)


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