Tom Watson wrote:
Read the Wall Street Journal article of last week, which references a
Science article of previous.

They are using MRE technology to direct a useful power across at least
three meters without wires.

Damned interesting.

I don't think that is only about frequency - but it certainly inhabits
the concept of specific resonant frequency.


This is a sort of unremarkable finding. Tesla did more-or-less the
same thing years ago. There are a myriad of issues here, not the
least of which is the effects on human tissue that such a technique
might engender when scaled sufficiently to be useful (assuming it
is practical as an engineering matter). See the comments at the
end of this article:

http://www.physorg.com/news100445957.html


--
----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/

Tom Veatch wrote:
... if the concept was
considered very high on the list, it would have received funding for at
least theoretical work. ...
The problem with those who are educated is that ...
Their predilection is to assume the veracity of the precedent, without
question.
...

When vacuum tubes were coming on line, there probably wasn't an awful
lot of funding for semiconductor research. "Invention" may be what's
needed rather than "development".


Certainly, but invention does not take place (so to speak) in a vacuum.
No innovation can violate demonstrated physical properties. Maxwell's
Equations that describe the governance of electromagnetic fields
have been with us for quite some time and seem unlikely to be
wrong. So, if we are to "innovate" in matters as discussed here,
there are really only two choices: A) There must be a fundamental
breakthrough in physics that changes all the known rules (possible
but unlikely) or B) We find a better way to engineer around the known
constraints of physics.

What Tom wants makes sense, but only in limited contexts, at least as
physics is understood today. Moreover, all engineering is a tradeoff
between features, time (to go to market) and *cost*. A modern wire
manufacturing facility is not a cheap thing to build. To justify what Tom
suggest, there has to be concrete economic advantage. If copper cost,
say, $3M per oz, that would be a compelling economic driver. But it
doesn't and the economics seems - at least at a casual glance - to favor
the status quo.

BTW, note that the transition from vacuum tubes to semiconductors was
not a fundamental shift in our understanding of amplification or
oscillation. It was a fundamental breakthrough in process technology.
That is, we discovered how to do what vacuum tubes were doing in a more
compact, and ultimately, less expensive way as a matter of
*engineering*. There was, of course, a corresponding breakthrough in our
understanding of the physics of semiconductors. Even so, semiconductors
never completely replaced vacuum tubes. Radio transmitters of any large
size still use tubes (valves to those of you in the rest of the
Anglosphere) because there are no transistors of which I am aware,
at least, than can deliver 50KW of RF into an antenna.

--
----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/

Tim Daneliuk wrote in
:

*trim*


P.S. There are no electrons, electricity is carried by teeny little
magic dwarfs with bad tempers and worse breath ...


Those teeny little magic dwarfs smoke a lot, don't they?

On Jun 15, 6:08 pm, Tom Watson wrote:
There have been a number of responses so far, many of which reference
the "skin effect" - why the hell do we continue to produce wire that
has a core of the same conductive capacity as the surface

At 60 Hz, the skin depth is inches (and wire a fraction of an inch
across is the norm). At higher frequencies, you see silver-plated
wire and most CATV cable is copper-plated iron for the central
wire. So, common wire products DO use less conductive
materials in the core.

On Fri, 15 Jun 2007 20:48:22 -0500, Tim Daneliuk
wrote:



I'm not sure where you're going with this. Skin Effect is
not an "assumption" - it can be calculated and probably even
measured.

At the Boston Museum of Science, there is a live demo where an
operator in a metal cage is hit by lightning while his or her hands
are against the inside of the cage. The lightning travels down the
outside of the cage.

http://www.mos.org/sln/toe/cage.html

Well worth the trip if in Boston!


---------------------------------------------
** http://www.bburke.com/woodworking.html **
---------------------------------------------

On Sat, 16 Jun 2007 02:27:09 -0500, Tim Daneliuk wrote:
Even so, semiconductors never completely replaced vacuum tubes. Radio
transmitters of any large size still use tubes (valves to those of
you in the rest of the Anglosphere) because there are no transistors
of which I am aware, at least, than can deliver 50KW of RF into an
antenna.

High-powered radar has been all solid state for some time. Many, many
peak KW at low duty cycle into the antenna. Continuous (AM, FM, TV) at
high power uses a number of smaller amplifiers with a split feed at the
input and a combiner at the output.

Back in 1975, I worked with solid state amplifiers in the ultrasound
range (30-50KHz) that delivered bursts of a single tone into a piezo
transducer. Several peak KW with two TO-3 transistors and no heatsink!

Today, Harris Broadcast sells an all solid-state 40KW FM broadcast
transmitter. I'm sure there are others, and for AM and TV as well.

--
Art Greenberg
artg at eclipse dot net

On Fri, 15 Jun 2007 20:33:23 -0500, Tim Daneliuk
wrote:

Tom Watson wrote:
There have been a number of responses so far, many of which reference
the "skin effect" - why the hell do we continue to produce wire that
has a core of the same conductive capacity as the surface, at great
cost, when we might manufacture a wire of a cheaper core material,
with the surface conductor at optimum.?


This is, in fact, done in some cases. I recall one 50KW broadcast
transmitter wherein a colleague of mine had to replace the tuning coils.
Instead of paying a small fortune to the manufacturer for what he
needed, he made his own out of ordinary copper water pipe - exactly
because the very high currents involved were carried on the surface of
the coil "winding" anyway. Note that this is not even particularly high
frequency stuff, the AM broadcast band running from about 500-1500 Khz.

Interestingly, he had to do this because the station had purchased a
used transmitter (50KW broadcast transmitters are NOT cheap) but it was
tuned to the wrong frequency. He reengineered it himself by changing the
aforementioned coil and a few other parts and got the thing to sit right
on the frequency they needed. As I understand it, they passed FCC
proof-of-performance handily.

And this is exactly the reason why smaller coils and cavities are
often silver plated copper. the whole thing doesnt need to be silver,
just the skin.

dickm

On Fri, 15 Jun 2007 19:43:14 -0400, Tom Watson
wrote:

The question that I asked him, which I thought to be simple enough,
was - do the electrons travel down the circumference of the wire, or
do they travel through the core of the wire?

This is _very_ well understood. If an "EE" doesn't understand this, I
can only assume they've spent their life working on 60Hz kit and never
gone near a radio.

Electrons go everywhere. At low frequencies, a substantial number are in
the middle of the conductor, and that might be a thick conductor.

If you consider a high frequency though, there's an exponential (i.e.
gradual) fall off with depth. This leads to "skin effect" and is why VHF
radios used to use Litz wire (many strands, so much more "surface to
diameter" ratio) and why VHF / UHF uses silver plating on the surface of
conductors. Above UHF, it's mostly waveguides rather than conductors.

On 16 Jun 2007 07:37:00 GMT, Puckdropper wrote:

P.S. There are no electrons, electricity is carried by teeny little
magic dwarfs with bad tempers and worse breath ...


Those teeny little magic dwarfs smoke a lot, don't they?

No, they don't usually smoke at all.

Until they all stop working for a massed fag break, where they now have
to go outside to do it.

On Fri, 15 Jun 2007 21:40:08 -0500, "Morris Dovey"
wrote:

Tom Watson wrote:
| There have been a number of responses so far, many of which
| reference the "skin effect" - why the hell do we continue to
| produce wire that has a core of the same conductive capacity as the
| surface, at great cost, when we might manufacture a wire of a
| cheaper core material, with the surface conductor at optimum.?

It's already been/being done. Check out wire for electrified fences at
your local farm store. Mild steel core with copper exterior. I used it
for building VHF transmit/receive antennas.

One more thing: VHF antennas work better when (a) wire diameter is
increased and (b) the wire is polished mirror bright.

I remember building 40M antennas out of Copperweld wire. A steel core
with a copper skin. You had to be careful with that stuff. Cut the
ties holding the coil of wire together and, BOING, like letting go of
a spring, you were immediately standing in the middle of a tangled
mess of wire that you didnt dare kink. It would take hours to
untangle.

dickm

"Tom Watson" wrote in message
...
There have been a number of responses so far, many of which reference
the "skin effect" - why the hell do we continue to produce wire that
has a core of the same conductive capacity as the surface, at great
cost, when we might manufacture a wire of a cheaper core material,
with the surface conductor at optimum.?

In high frequency situations we don't Tom. Conductors for such things as
radio towers are often hollow core conductors.


--

-Mike-

"Tom Watson" wrote in message
news
Not with the intent of giving offence but -

That is a particularly shabby piece of reasoning.


Not with the intent of giving offence but -

Yours is a particularly baseless argument, seemingly overly fond of your own
insightfulness.

--

-Mike-

"todd" wrote in message
news

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.


That has the sound of stating that the EE's are missing the obvious benefits
of applying these principles universally. As you so properly stated though,
they are being applied in the relevant industries. The operative part of
that is the word "relative".

--

-Mike-

In article , Tom Watson wrote:
Don't know whether they thought to check, or not.

Don't really know how someone who isn't really creative via
personality might be encouraged to think outside the box created for
them - that made them part of their personal cognoscenti.

I think you're making a fundamentally mistaken assumption here, that engineers
are people "who aren't really creative via personality." If nothing else, the
thousands of patents granted every year would suggest otherwise. Creativity
occurs in other areas besides the fine arts, you know.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Tom Watson wrote:
Tim:

Let's say that I admit all that you present.

The fundamental question still stands.,

Why do we insist on producing conductors composed of very expensive
core materials, when we could achieve the same effect, or better, by
coating the core material with a highly conductive skin?


Copper clad steel ground rods are common.

HF tank circuits using silver plated copper are common.

Nothing novel about what you are saying. As the table of skin depths
shows, the value is very dependent on the frequency of use. For DC or
normal house wiring there is no benefit.

John

On Jun 15, 7:43 pm, Tom Watson wrote:
I had a conversation with a friend of mine today who has a masters in
electrical engineering.

This degree was conferred by the same school that I went to
(Villanova) about a hundred years ago, so I must inherently trust him.

Yet...

The question that I asked him, which I thought to be simple enough,
was - do the electrons travel down the circumference of the wire, or
do they travel through the core of the wire?

He told me that that is an unknown.

This was very surprising to me as I thought that it would be easily
tested.

Could we not create a wire of a core of inert material and coat it
with a conductor and measure the difference between a wire of the pure
element and that of the coated variety?

This seemed to be not within his reckoning.

The reason that it is important, to me, is that, if the electrons only
travel on the circumference, that circumference may be folded into a
smaller section than that described by the original, and wires would
not have to be so thick.

Would y'all please try to help me out of this conundrum?

Is my friend a poseur?

Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/



Hello Tom,
You're post has brought out some erudition on the subject of electical
engineeering. If this keeps up I suspect our NG will be discussing
entropy and a deeper understanding of gravity, with respect to
woodworking of course.
Joe G

Doug Miller wrote:


I think you're making a fundamentally mistaken assumption here,

Imagine my surprise.....

Tom Watson wrote:

Why do we insist on producing conductors composed of very expensive
core materials, when we could achieve the same effect, or better, by
coating the core material with a highly conductive skin?

Because it's cheaper? I used to work, many eons ago, for American Steel and
Wire in North Chicago. Plain old drawn copper or aluminum or whatever was
cheap to produce. Plating was expensive. I don't know if that's still the
case or not, but I'd guess it is.

--
It's turtles, all the way down

Art Greenberg wrote:
On Sat, 16 Jun 2007 02:27:09 -0500, Tim Daneliuk wrote:
Even so, semiconductors never completely replaced vacuum tubes. Radio
transmitters of any large size still use tubes (valves to those of
you in the rest of the Anglosphere) because there are no transistors
of which I am aware, at least, than can deliver 50KW of RF into an
antenna.

High-powered radar has been all solid state for some time. Many, many
peak KW at low duty cycle into the antenna. Continuous (AM, FM, TV) at
high power uses a number of smaller amplifiers with a split feed at the
input and a combiner at the output.

Back in 1975, I worked with solid state amplifiers in the ultrasound
range (30-50KHz) that delivered bursts of a single tone into a piezo
transducer. Several peak KW with two TO-3 transistors and no heatsink!

Today, Harris Broadcast sells an all solid-state 40KW FM broadcast
transmitter. I'm sure there are others, and for AM and TV as well.


Interesting. I used to service marine Radars, and while their peak
output power was in the 10-50 KW range, their average power was far
lower because of the low duty cycle. When you say that radars have
been solid state for some time, does that mean magnetrons and klystrons
are no longer in the picture? (Not arguing, just curious.)

--
----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/

On Sat, 16 Jun 2007 13:35:31 GMT, (Doug Miller)
wrote:

I think you're making a fundamentally mistaken assumption here, that engineers
are people "who aren't really creative via personality." If nothing else, the
thousands of patents granted every year would suggest otherwise. Creativity
occurs in other areas besides the fine arts, you know.

Excellent point.

---------------------------------------------
** http://www.bburke.com/woodworking.html **
---------------------------------------------

On Sat, 16 Jun 2007 11:24:17 -0500, Tim Daneliuk wrote:
When you say that radars have been solid state for some time, does
that mean magnetrons and klystrons are no longer in the picture?
(Not arguing, just curious.)

I'm pretty sure that cost still dictates magnetron transmitters in
recreational (marine) and virtually all commercial radars. I
spot-checked a few Furuno and Raymarine units between 4KW and 60KW, and
they use magnetrons. I wasn't able to find any on-line references to
klystron based units. I also wasn't able to find any on-line product
brochures or other evidence of commercially available all solid-state
radars, which surprises me greatly.

Back when I was a little closer to this, in the early 90s, there was
work being done to put together all solid-state radar transmitters. But
the transistors of that era were unable to do make very high peak power
pulses needed for high resolution returns. There was discussion of using
signal processing techniques in both the transmitter and receiver to
compensate for longer pulse durations. But at the time, that kind of
processing was costly. It certainly should be much more in reach today.

I was able to find a few items on-line that talk about military
solid-state radar dating to as early as 1992, and a report about an FAA
test of a solid-state ASR in 1994.

--
Art Greenberg
artg at eclipse dot net

dicko wrote:

| I remember building 40M antennas out of Copperweld wire. A steel
| core with a copper skin. You had to be careful with that stuff.
| Cut the ties holding the coil of wire together and, BOING, like
| letting go of a spring, you were immediately standing in the middle
| of a tangled mess of wire that you didnt dare kink. It would take
| hours to untangle.

SOP was to tie one end around a tree and the other end around a car
bumper (remember when we could do that?) and let the car creep
foreward until the tightness could be either heard (twunggg) or felt.

When the wire was snipped (next to the knots) it would stay as
straight as you please. :-)

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Art Greenberg wrote:

they use magnetrons. I wasn't able to find any on-line references to
klystron based units. I also wasn't able to find any on-line product

The klystrons were used as local oscillators for the receiver.
In the smaller units, the magnetron was excited by a solid state
modulator circuit, but in the larger (25KW and up) commercial
marine units I worked on (Decca, Furuno, Kelvin Hughes) the modulators
where "valves", aka tubes


--
----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/

B A R R Y wrote:
On Fri, 15 Jun 2007 20:48:22 -0500, Tim Daneliuk
wrote:


I'm not sure where you're going with this. Skin Effect is
not an "assumption" - it can be calculated and probably even
measured.

At the Boston Museum of Science, there is a live demo where an
operator in a metal cage is hit by lightning while his or her hands
are against the inside of the cage. The lightning travels down the
outside of the cage.

http://www.mos.org/sln/toe/cage.html

Well worth the trip if in Boston!



Just bear in mind that lightning is an electroSTATIC phenomenon not
electroMAGNETIC one. It's been way to many years since I actually
had to know anything about this stuff, but IIRC, the behaviors
of electrostatics are governed by rather different mathematics
than electromagnetics (which are described by Maxwell's Equations).
So ... what you see at the museum is not exactly the same thing
under discussion here. It's still fun to watch though

--
----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/

On Sat, 16 Jun 2007 15:24:42 -0500, Tim Daneliuk
wrote:

Just bear in mind that lightning is an electroSTATIC phenomenon not
electroMAGNETIC one. It's been way to many years since I actually
had to know anything about this stuff, but IIRC, the behaviors
of electrostatics are governed by rather different mathematics
than electromagnetics (which are described by Maxwell's Equations).
So ... what you see at the museum is not exactly the same thing
under discussion here. It's still fun to watch though

It is, and thanks for the clarification.

Maxwell's equations wouldn't mean much to me, but I'm currently
reading:

http://www.amazon.com/gp/product/customer-reviews/067003441X/ref=cm_cr_dp_all_helpful/104-7024228-0566367?ie=UTF8&n=283155#customerReviews




---------------------------------------------
** http://www.bburke.com/woodworking.html **
---------------------------------------------

Tom first off.... I've seen them plate aluminum wire with copper and copper
cores plated with carbon. Cost not performance the factor... Secondly as
much BS as there is electrons flow the path of least resistence but
basically it's the whole hose principle..... Current is the controlling
factor. Put a 20g wire under 20A and watch it fail.

Copper will easily be cheaper then "gold" plating the wire. and essentually
you'll find plenty of it (gold plated) where humidity and environment is a
factor to oxidation and corrosion more so then low current loads like Scada
data leads or Hi-Def Audio circuitry.


"Tom Watson" wrote in message
...
There have been a number of responses so far, many of which reference
the "skin effect" - why the hell do we continue to produce wire that
has a core of the same conductive capacity as the surface, at great
cost, when we might manufacture a wire of a cheaper core material,
with the surface conductor at optimum.?

Wouldn't it make more sense to create a wire of a cheap core, with a
surface at optimum? We could have gold plated wires that would be
cheaper than solid copper.

On Fri, 15 Jun 2007 19:43:14 -0400, Tom Watson
wrote:

I had a conversation with a friend of mine today who has a masters in
electrical engineering.

This degree was conferred by the same school that I went to
(Villanova) about a hundred years ago, so I must inherently trust him.

Yet...

The question that I asked him, which I thought to be simple enough,
was - do the electrons travel down the circumference of the wire, or
do they travel through the core of the wire?

He told me that that is an unknown.

This was very surprising to me as I thought that it would be easily
tested.

Could we not create a wire of a core of inert material and coat it
with a conductor and measure the difference between a wire of the pure
element and that of the coated variety?

This seemed to be not within his reckoning.

The reason that it is important, to me, is that, if the electrons only
travel on the circumference, that circumference may be folded into a
smaller section than that described by the original, and wires would
not have to be so thick.

Would y'all please try to help me out of this conundrum?

Is my friend a poseur?





Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

IIRC, they tend to gravitate towards the circumference. Google 'eddy
currents' and you might turn up something. It was taught to me this is
one of the reasons that stranded wiring (in heavy duty applications)
works better. Obviously, stranded is easier to work with, also.
I'll watch this thread to se if I'm on the right track....
Mark

You must have gone the same school as me, years ago.

Pete

Tom Watson wrote:
I had a conversation with a friend of mine today who has a masters in
electrical engineering.

This degree was conferred by the same school that I went to
(Villanova) about a hundred years ago, so I must inherently trust him.

Yet...

The question that I asked him, which I thought to be simple enough,
was - do the electrons travel down the circumference of the wire, or
do they travel through the core of the wire?

He told me that that is an unknown.

This was very surprising to me as I thought that it would be easily
tested.

Could we not create a wire of a core of inert material and coat it
with a conductor and measure the difference between a wire of the pure
element and that of the coated variety?

This seemed to be not within his reckoning.

The reason that it is important, to me, is that, if the electrons only
travel on the circumference, that circumference may be folded into a
smaller section than that described by the original, and wires would
not have to be so thick.

Would y'all please try to help me out of this conundrum?

Is my friend a poseur?





Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

Wow, small things can occupy small minds. I know fer shure this's the first
place I'd ask a fisics kwestion!

Pop`

Andy Dingley wrote:
On 16 Jun 2007 07:37:00 GMT, Puckdropper
wrote:

P.S. There are no electrons, electricity is carried by teeny little
magic dwarfs with bad tempers and worse breath ...


Those teeny little magic dwarfs smoke a lot, don't they?

No, they don't usually smoke at all.

Until they all stop working for a massed fag break, where they now
have to go outside to do it.

The trouble is that when they do that you can't get them to go back to
work.

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

Tim Daneliuk wrote:
Tom Watson wrote:
Read the Wall Street Journal article of last week, which references a
Science article of previous.

They are using MRE technology to direct a useful power across at
least three meters without wires.

Damned interesting.

I don't think that is only about frequency - but it certainly
inhabits the concept of specific resonant frequency.


This is a sort of unremarkable finding. Tesla did more-or-less the
same thing years ago. There are a myriad of issues here, not the
least of which is the effects on human tissue that such a technique
might engender when scaled sufficiently to be useful (assuming it
is practical as an engineering matter). See the comments at the
end of this article:

http://www.physorg.com/news100445957.html

Somebody demonstrated a model helicopter flying by transmitted power in
the '60s and Gerard K. O'Neill designed a system that would transmit
power from orbit in gigawatt quantities.

Using it for cell phones and the like, one might be able to have a local
charger in one's car or on one's desk that charges the phone without
having to plug it in, but having all cell phones charged from a central
power transmitter is unlikely in the extreme.

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

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)

... if the concept was
considered very high on the list, it would have received funding
for at least theoretical work. ...

The problem with those who are educated is that ...
Their predilection is to assume the veracity of the precedent,
without question.
...

When vacuum tubes were coming on line, there probably wasn't an awful
lot of funding for semiconductor research. "Invention" may be what's
needed rather than "development".

It never occurred to anybody that a semiconductor device could replace a
vacuum tube for any purpose other than as a rectifier until Shockley
came up with the idea in the mid-1940s of the transistor, and he
couldn't have done that without a great deal of research into the nature
of semiconductors, which research was the result of a need in radar
development for low-inductance components.

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

Tom Watson wrote:
Not with the intent of giving offence but -

That is a particularly shabby piece of reasoning.




I marked the thread with an OT because I'm trying to be helpful and Tom
apparently forgot to do it.

But, as regards the reasoning, I have to agree with Tom. For many years
there were some really, really bright people working on heavier than air
flight Da Vinci, for one) ... and a couple of bicycle mechanics from
Ohio share the honors with a Latin American bon-vivant for solving the
basic problems.

While Goddard gets much of the credit for space flight, a lot of very
intelligent Chinese had solved most of the problem centuries earlier ...
but never finished up.

It's hard to point at any single area of life and say 'IF there was an
answer THESE people would know what it is.' I can say it ... but it's
hard to keep a straight face.

I do rather suspect that enough research would reveal that the question
has already been considered since one of the areas engineers are often
found considering is price.

Bill


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I've had a bit of time to refine my understanding of the real world
problem that engendered this inquiry.

We are trying to run a carrier in a trough that is 1/2" wide by 3/4"
deep. This carrier will feed five LED arrays that are composed of 54
Watts each.

The maximum length of the run is 100 feet.

I was worried that the wire would have to be of such a size that it
would not fit, and, more importantly, the connectors would not fit, in
the available volume.

It seems to be the case that I need not have worried.

BTW - my apologies for the apparent disparagement of engineers in my
post. I was actually responding to one person, but tarred the
profession with the same brush.

I have the greatest respect for engineers and deal with them on a more
or less daily basis.

That one guy ****ed me off and I shot back at him. My apologies to
those who were caught in the crossfire.


Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/On Fri, 15 Jun 2007 19:43:14 -0400,
Tom Watson wrote:

I had a conversation with a friend of mine today who has a masters in
electrical engineering.

This degree was conferred by the same school that I went to
(Villanova) about a hundred years ago, so I must inherently trust him.

Yet...

The question that I asked him, which I thought to be simple enough,
was - do the electrons travel down the circumference of the wire, or
do they travel through the core of the wire?

He told me that that is an unknown.

This was very surprising to me as I thought that it would be easily
tested.

Could we not create a wire of a core of inert material and coat it
with a conductor and measure the difference between a wire of the pure
element and that of the coated variety?

This seemed to be not within his reckoning.

The reason that it is important, to me, is that, if the electrons only
travel on the circumference, that circumference may be folded into a
smaller section than that described by the original, and wires would
not have to be so thick.

Would y'all please try to help me out of this conundrum?

Is my friend a poseur?





Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

Tom Watson wrote:
I've had a bit of time to refine my understanding of the real world
problem that engendered this inquiry.

We are trying to run a carrier in a trough that is 1/2" wide by 3/4"
deep. This carrier will feed five LED arrays that are composed of 54
Watts each.

The maximum length of the run is 100 feet.

I was worried that the wire would have to be of such a size that it
would not fit, and, more importantly, the connectors would not fit, in
the available volume.

It seems to be the case that I need not have worried.

BTW - my apologies for the apparent disparagement of engineers in my
post. I was actually responding to one person, but tarred the
profession with the same brush.

I have the greatest respect for engineers and deal with them on a more
or less daily basis.

That one guy ****ed me off and I shot back at him. My apologies to
those who were caught in the crossfire.


Regards,

Tom Watson


S'OK Tom - we engineers are not only rather creative - we're a forgiving
lot


----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/

On Fri, 15 Jun 2007 20:48:22 -0500, Tim Daneliuk
wrote:

In Engineering Electromagnetics, Hayt points out that in a power station
a bus bar for alternating current at 60 Hz with a radius larger than
1/3rd of an inch (8 mm) is a waste of copper, and in practice bus bars
for heavy AC current are rarely more than 1/2 inch (12 mm) thick except
for mechanical reasons.

I've never seen busbars much thicker than that, even in DC systems.

I used to work in telephone exchanges, back in the days of Strowger etc.
_Lots_ of power was needed to run an exchange, all distributed at 50V
DC. The bus bars were copper strip, about 1/2" from memory and up to 12"
wide. Generally the thickness was standard everywhere, but the width was
proportional to the current for that citcuit. For a really big feed,
such as the one from the battery room downstairs, these busbars would be
paralleled up and spaced slightly apart. Mainly this was done for ease
of mechanically forming busbars, as two 1/2" strips are easier to
install than one 1" strip. It also meant thought that skin effect
wouldn't have been a problem, even at 50Hz.

On Sat, 16 Jun 2007 15:24:42 -0500, Tim Daneliuk
wrote:

Just bear in mind that lightning is an electroSTATIC phenomenon not
electroMAGNETIC one.

It isn't. You might generate lightning by a static phenomenon, but if a
current flows (ie there's a flash) then it will also generate the
magnetic effects.

There's also the question of Tesla coils, which are AC anyway. Most of
the museum "lightning demonstrations" you see are done with Teslas,
rather than an electrostatc machine. Except in Boston though, where they
still have that huge Van de Graaff generator that's sometimes used for
"geek in a cage" shows.

On Sat, 23 Jun 2007 12:02:28 +0100, Andy Dingley

There's also the question of Tesla coils, which are AC anyway. Most of
the museum "lightning demonstrations" you see are done with Teslas,
rather than an electrostatc machine. Except in Boston though, where they
still have that huge Van de Graaff generator that's sometimes used for
"geek in a cage" shows.

Daily! G

---------------------------------------------
** http://www.bburke.com/woodworking.html **
---------------------------------------------

Thanks Tim.

I dislike being tarred with the same brush and seek to not do same in
my life with others.

In this instance I reacted emotionally, and I regret it.

Thank you for your forbearance.



On Thu, 21 Jun 2007 23:37:13 -0500, Tim Daneliuk
wrote:

Tom Watson wrote:
I've had a bit of time to refine my understanding of the real world
problem that engendered this inquiry.

We are trying to run a carrier in a trough that is 1/2" wide by 3/4"
deep. This carrier will feed five LED arrays that are composed of 54
Watts each.

The maximum length of the run is 100 feet.

I was worried that the wire would have to be of such a size that it
would not fit, and, more importantly, the connectors would not fit, in
the available volume.

It seems to be the case that I need not have worried.

BTW - my apologies for the apparent disparagement of engineers in my
post. I was actually responding to one person, but tarred the
profession with the same brush.

I have the greatest respect for engineers and deal with them on a more
or less daily basis.

That one guy ****ed me off and I shot back at him. My apologies to
those who were caught in the crossfire.


Regards,

Tom Watson


S'OK Tom - we engineers are not only rather creative - we're a forgiving
lot


----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

In article ,
Tom Watson wrote:
Tim:

Let's say that I admit all that you present.

The fundamental question still stands.,

Why do we insist on producing conductors composed of very expensive
core materials, when we could achieve the same effect, or better, by
coating the core material with a highly conductive skin?


Wading in very late on this discussion, but the answer to virtually every
question of the general form "why don't they do ..." is very simple.
"Money".

And, in the specific instance you raise, Tom, the answer is "In the situations
where it makes economic sense to do so, they *do*, and have, for _many_ years."

One of the more common examples is 'hollow tubes' used at RF frequencies.
One can't get much cheaper than air for a 'core material'. grin
It's amazing how much RF energy at even AM radio frequencies that, say
1/2" copper water tubing can carry.

Most high-power microwave waveguides -- which are nothing more than a thin
layer metal surrounding an air core -- *are* _GOLD_ plated. Have been, for
*decades*. For exactly the reasons you the designers of _not_ considering.

'Solid' conductors made of dissimilar materials introduce a raft of other
engineering issues. Differing 'coefficient of expansion' in the materials
can introduce _major_ stresses, contributing to *GREATLY* reduced life-span.
If you reduce the 'cost' by 20%, but the life-span is reduced by 50% you
_are_ at a net loss.

In addition, 'bi-metallic' conductors are *MUCH* more expensive to manufacture
than ones of monolithic construction. There is a lot more to building wire
than just the 'cost of materials'.

And, the fact remains, that at 'power line' frequencies, the 'skin effect' is
minimal, except on _very_ large cables.

The _killer_ is that "very large" cables are a _bad_choice_ *economically*.
One can move the same amount of energy over a *smaller* cable, by simply using
a higher voltage. Which is more efficient for other reasons as well.

In short, the question you raise is a "solved problem". The physics haven't
changed in the last 50 years, although manufacturing techniques have. And
folks like the E.P.I. _do_ keep an eye on developments in the manufacturing
arts. If a 'solution' comes along that is _cheaper_ than present methodologies,
they *WILL* jump on it.

Example: substations and switchyards use a lot of rigid hollow-tube 'wiring'.
For *short* runs, where you don't have 'parabolic sag' issues, it is more
effective than conventional wire. Over longer spans, however, conventional
'solid core' wire strands "win", because of the 'adaptability' and consequent
less frequent need for support structures.


Summary: Your 'bright idea' is *well-known* in the industry, and has been
used for many _decades_ in contexts where it makes economic sense to do so.
You don't see much about it, because it is such _common_practice_ in the areas
where it is economically viable that nobody bothers to talk about it -- it *is*
just the way 'everybody does it'.