On 8/28/2013 6:36 PM, Fuqua, Bill L wrote:
In a workshop I teach, I explain to young students how current flows thru
conductors.
I put them all in a circle and insert myself into the circle. Then I tell them
that they are the
atoms that make up the conductor and I am a battery, I give each a shinny new
penny with
a negative sign on both sides. I then tell them that the pennies are free
electrons and being
the battery my job is to take them in one hand and hand them out on the other.
So I take one penny
into my positive hand from the first student, and telll him that now he is
positive and must take one from
his neighbor. This continues until the student on my negative side is short an
electron (penny) and I
give that student another penny.
In an introductory course we had to figure out the average speed of the
electron drift in a #10 wire carrying 1 Amp.
Like the pool ball experiment the one entered and the other popped out
almost instantly, but the average speed was somewhat faster than a fast
walk IIRC. It's quite possible that the original electron never did
make it to the other end.
Although it was a fairly easy exercise, I don't remember the steps,
other than all atoms were considered to have a free electron. The
number of electrons in a coulomb, and Avogadro's number for atoms in a
mole of copper.
Anyone remember how to do that?
73
Roger (K8RI)
While doing this one day, we started going faster and faster until
something went wrong.
A boy had two pennies and the girl next to him had none. I said, now we have a
problem, remember, these are
young elementary students. I told the boy that now he is negative, and the girl
is positive. One kid pointed
out that they must be attracted to one another. The boy and girl both said
"yuck".
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Fuqua, Bill L
[wlfuqu00@uky.edu]
Sent: Wednesday, August 28, 2013 6:23 PM
To: Roger (K8RI); amps@contesting.com
Subject: Re: [Amps] Electron HOLE flow
sometimes I fell like Ben, given a 50-50 chance I always get it wrong.
Bill
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Roger (K8RI)
[k8ri@rogerhalstead.com]
Sent: Wednesday, August 28, 2013 5:56 PM
To: amps@contesting.com
Subject: Re: [Amps] Electron HOLE flow
On 8/28/2013 2:05 PM, Mike Waters wrote:
Absolutely it is an illusion. IIRC, that was erroneously introduced into
textbooks around 1970 the same time as the "electricity flows from positive
to negative" nonsense. Whoever came up with the latter never heard of
electron flow in a vacuum tube, among other things.
You are quite right. The vacuum tube hadn't been invented yet when + to
- (conventional current) was defined although you're a bit off on the
date. EEs have used conventional current since there have been EEs and
it was defined by Ben Franklin.
73
Roger (K8RI)
73, Mike
www.w0btu.com
On Wed, 28 Aug 2013 03:54:29 -0400, K8RI wrote:
They still refer to "hole flow" in introductory semiconductors.
REPLY:
"Hole flow" is an illusion, much like the moving lights on a theater
marquee. If it helps to understand things fine, but holes don't move. It's
more accurate to say a hole is created in one atom and disappears in
another. For a brief time while the electron is in motion, there are
actually two holes. Neither one "moves".
73, Bill W6WRT
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