Quite a bit, actually - it's just that there is an equal amount
of positive and negative charge. If all of those eight
trillion electrons could magically be removed (that's a pretty
small piece of wire, by the way), how much charge would
there be then?
But the ability of a conductor to conduct current is not dependent upon how
many electrons it has, but rather how easily those electrons may be induced
to move. A piece of glass and a piece of copper with equal amounts of
electrons will have an equal *net* charge of zero in the idealized absence
of an electric field. When a field is introduced - the application of a
potential from one end to the next, the copper will much more easily
acquire net charge differences at the molecular level. So, let's modify my
statement to say that a piece of wire with no electric field present will
have no net positive or negative charge.
Fundamentally, "charge" refers to a basic property of
subatomic particles, namely that property which causes
them to produce an electric field. (Or at least that is one
aspect of it - the fundamental force involved is the
electromagnetic force, which also is responsible for
magnetic fields.)
So let's apply this to the statement I replied to:
"charge is a a number of electrons (or equivalent)"
That's very inaccurate. Let's get down to fundamentals, and look at how
current is defined in a physical model. I'll substitute English letters
for the Greek that is standard in the definition
I = pn*q*vd*A
vd = Drift Velocity
pn = Number Density - Charges per unit Volume
q = Magnitude of the charge on each moving charge
A = Cross-sectional Area perpendicular to the flow.
So, charge can't be said to be a "number of electrons" unless there is some
quantity that produces a charge due to the presence of potentially free
electrons - IOW you won't have net positive or negative charge until
something gets electrons moving. Am I correct so far?
We can short this whole argument to ground (no
pun intended..
) by simply noting that "current" (which
is what "amperes" are used to quantify) is not
technically the movement of charged particles themselves,
necessarily, but rather the EFFECTIVE movement
of charge. The addition of that one little word lets us
talk reasonably about alternating current; even though
there is no real net movement of charge carriers in
one direction over the other, there IS a flow of "energy"
which can be quantified by using notions of current, etc.,
just as if everything was "flowing" in one direction (as
in the case of DC). This is just one of those areas where
our mental model than uses a stream of water (or
whatever) as an analog for electricity starts to look a
little problematic. But once you remember that it
really IS just a model, and not precisely a description
of the real thing, the problems go away.
Well I think that definition is pretty good, and I don't think it differs
much from what I am trying to say. My comment comes from being a bit
baffled by seeing current being referred to as the movement of potential,
instead of the movement of charge. I'd like to see that explained. I
mean, I can see that across a conductor that is conducting charge, that in
taking slices of that conductor and measuring potential, one can see that
potential changes over the linear distance of measurement. But how can
that lead to a definition of current as being a movement of potential?! I
just don't think that's right.
Let's take an example from a thread from a month or so ago, regarding the
propagation of an electric field through the air. It can be seen and
measured that the field strength decreases with distance from the
transmitter. May that be considered a movement of potential? It is a
travel ling electric field, but it is not current. Indeed, several posters
were insisting that it's not even electricity. So, can we reconcile that
definition? Or not?
