todd wrote:
Tom Veatch wrote in message
...
On Fri, 15 Jun 2007 20:50:12 -0500, dpb wrote:


Trust me, there are some _REALLY, REALLY BRIGHT_ folks who do this
stuff for a living -- if it were feasible, they would have already
done it...

Believe me, I'm not trying to be a wiseass, but there were some
"REALLY, REALLY BRIGHT" folks in the 1800's. So why didn't they
"already done" semiconductor devices?

The point is, we don't know all there is to know about (fill in the
blank). Right up until Kitty Hawk really bright people were insisting
that heavier than air powered flight was impossible - even though
gliders had been around for years.

Ease up on the analogies. We're not talking about having to invent a
superconductor. The actual products that Tom is wishing someone
would use are already in existence in relevant industries, they're
just not being used in quite the way that Tom is contemplating. It's
just that electrical engineers aren't creative enough to connect the
dots.

Tom's trying to oversimplify a complicated question and then produce an
engineering design based on that oversimplified analysis.

Electrons in a conductor flow wherever the electromagnetic field in the
conductor causes them to flow. At DC levels the field is more or less
uniform throughout the conductor so they'll move more or less uniformly
through the entire cross section. At AC levels where skin effect
becomes an issue the electrons will flow more heavily near the surface
than at the center, with the details depending on the geometry, the
frequency, and the current.

The trouble with his notion of using "thin coatings" is that there still
has to be enough cross sectional area to carry the current. At 60 Hz AC
levels, trying to use a "thin coating" for household wiring doesn't gain
you anything--the diameter of a solid conductior is much less than the
skin thickness and making the conductor a shell wouldn't reduce the
amount of conductive material needed, it would just make the conductor
more costly to manufacture and more difficult to handle. In substations
at very high currents the diameter of the conductor becomes large
relative to the skin thickness and it becomes beneficial to use his
"thin coating" in the form of tubular busbars. This is also done in the
aforementioned aluminum clad steel transmission lines, however in that
case the hollow center is in effect filled with the steel structural
element.

As for his electrical engineer friend, EEs don't generally deal with
electrons unless they're designing vacuum tubes, they deal with
fields--for the distribution of electrons in a conductor he'd really
have to ask a solid state physicist.

--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)