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 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/
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

On Jun 15, 4:58?pm, Mark wrote:
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/

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- Hide quoted text -

- Show quoted text -

When I took grounding and shielding from Ralph Morison the first thing
he said was that you need to remember two things 1) all electrical
energy is contained in fields.
2) ohms law works.

the electrical field is defined by the boundaries of the conductors.

GeneK

In article , 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?

No, I don't think your friend is a poseur, but I don't think he completely
understood the drift of your question, either.

In an alternating-current circuit, electric *charge* travels on the surface of
the conductor, and to some depth below the surface. Google on "skin effect"
for more information, or ask your friend; I'm sure he must be familiar with
the concept. Moving electric charge is not quite the same as moving electrons,
and if you phrased your question specifically with regard to electrons, he may
not have made the connection to skin effect -- especially if you didn't tell
him why you wanted to 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 in message
...


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

Is my friend a poseur?


Can't say anything about your friend, because I've never met him. But... I
do recall from days gone by, that as frequency increases, skin effect
becomes more of a factor. Seems to me that at least at one time, it was
believed that electrons only traveled the skin at these high frequencies.

--

-Mike-

"Tom Watson" wrote in message
...
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/

It's been a while, but my remembrance is that as the frequency increases, a
larger portion of the electrons travel on the surface of the wire (skin
effect, see http://en.wikipedia.org/wiki/Skin_effect). So, your idea may
work for high frequencies, but probably not for low frequencies/DC. Some
high frequency circuits (coils, particularly) are built using Lenz wire
(spelling?) which is made up of many strands of very fine wire. Since the
high frequency current flows along the surface, and there's a lot more
surface to the many strands, this bunch of wires can conduct more current
than a single wire of the same outside diameter could.
Real ee's may be able to offer a more correct explanation.
Kerry

1st point: this is not a woodworking discussion

You did not specify if the current was AC or DC. If it's DC the
current would more or less evenly spread throughout the wire. If the current
is AC Maxwell's equation's force the electron's to travel on the outer
surface of the wire, with a quick lowering of current density as you got
closer to the center.
The AC model is fairly certain, the DC model is almost entirely
based on theory.
Your folded wire would still have the electrons travelling on the outer
edges while carrying an AC current.
I see no problems with the answer your friend gave based on the question you
asked.

BS in physics and electrical engineering.

"Tom Watson" wrote in message
...
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:

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?

Good question.

You could compare a solid conductor V a tubular conductor made of the
same materials and of the same length at various currents and frequencies.

To paraphrase an old chief engineer of mine, "Give us a year and $500K
and we will define the problem for you."

Lew

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?

It depends on the frequency of the signal, IIRC. As frequency rises
the tendency is conduct along the surface of the conductor. This is
(if I can remember that far back) called "skin effect".
----------------------------------------------------------------------------
Tim Daneliuk
PGP Key: http://www.tundraware.com/PGP/

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/

JP wrote:
....
You did not specify if the current was AC or DC. If it's DC the
current would more or less evenly spread throughout the wire. If the current
is AC Maxwell's equation's force the electron's to travel on the outer
surface of the wire, with a quick lowering of current density as you got
closer to the center.
....

And, the effect is used in higher-end of the HV transmission lines --
the three conductors relatively close together in a triangle are a
"virtual" wire acting in concert...

--

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.?



I think this is all about frequency. At 60hz I don't believe this
buys you much, but at Mhz/Ghz freqs it might ...

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

Tim Daneliuk wrote:
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?

It depends on the frequency of the signal, IIRC. As frequency rises
the tendency is conduct along the surface of the conductor. This is
(if I can remember that far back) called "skin effect".
----------------------------------------------------------------------------

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

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

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

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.?



I think this is all about frequency. At 60hz I don't believe this
buys you much, but at Mhz/Ghz freqs it might ...


Oh, in a related note ... In my misspent youth, I installed/repaired
High Frequency Single Sideband Radios for fishing boats in Alaska.

Many of these vessels were wooden and ground is rather important when
designing HF radio antennas. We could typically find good ground at the
heat exchanger in the bilge of the ship which was metal and in contact
with the ocean.

The problem always was that these are typically pretty far away (20-100
feet) from the wheelhouse. If we used wire to get to ground, that wire
then actually became a radiator of radio energy - which is not what you
want from a ground.

So, we used copper flashing which was very thin but *Wide*. At HF
frequencies, area turns out to be a big deal for ground planes. In the
worst case, we'd use 00 or even 0 welding cable to get to a real ground
because - IIRC - the effective area of a wire is something like 2-3x its
diameter.




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

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.?

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.


As most of those postings noted, the "skin effect" is really only of
significance and high frequency (far above the 60 Hz AC). The solution
of Maxwell's equations is dependent on the material and changing the
core material changes the behavior as well. A combination of materials
_might_ be effective, but certainly until very recently the cost
differential of manufacture w/ multiple materials far outweighs the
benefits. It _might_ be getting to the realm of reasonable, but while
I've not investigated it as a real possibility, I really doubt even yet
we're to that point on material costs relative to other costs.

The electric utilities spend a great deal on research and I spent a
sizable fraction of my career in the utilities business working w/ EPRI
(Electric Power Research Institute, a utility-funded R&D organization)
in the I&C and Transmission & Distribution areas and if the concept was
considered very high on the list, it would have received funding for at
least theoretical work. To the best of my knowledge it hasn't.

Where we could _really_ make a savings would be to get practical
near-room-temperature or at least not near-absolute-zero
superconductors--they're making progress, but a ways to go yet.

--


For transmission

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.


On Fri, 15 Jun 2007 20:15:53 -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.?



I think this is all about frequency. At 60hz I don't believe this
buys you much, but at Mhz/Ghz freqs it might ...
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

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.


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

On Fri, 15 Jun 2007 20:26:23 -0500, dpb wrote:



The electric utilities spend a great deal on research and I spent a
sizable fraction of my career in the utilities business working w/ EPRI
(Electric Power Research Institute, a utility-funded R&D organization)
in the I&C and Transmission & Distribution areas and if the concept was
considered very high on the list, it would have received funding for at
least theoretical work. To the best of my knowledge it hasn't.


The problem with those who are educated is that they have been trained
off the obvious.

Their predilection is to assume the veracity of the precedent, without
question.

I'm asking you to revisit the fundamental assumptions.


Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

You are moving towards my theory on this, Tim.


On Fri, 15 Jun 2007 20:24:33 -0500, Tim Daneliuk
wrote:

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.?



I think this is all about frequency. At 60hz I don't believe this
buys you much, but at Mhz/Ghz freqs it might ...


Oh, in a related note ... In my misspent youth, I installed/repaired
High Frequency Single Sideband Radios for fishing boats in Alaska.

Many of these vessels were wooden and ground is rather important when
designing HF radio antennas. We could typically find good ground at the
heat exchanger in the bilge of the ship which was metal and in contact
with the ocean.

The problem always was that these are typically pretty far away (20-100
feet) from the wheelhouse. If we used wire to get to ground, that wire
then actually became a radiator of radio energy - which is not what you
want from a ground.

So, we used copper flashing which was very thin but *Wide*. At HF
frequencies, area turns out to be a big deal for ground planes. In the
worst case, we'd use 00 or even 0 welding cable to get to a real ground
because - IIRC - the effective area of a wire is something like 2-3x its
diameter.
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

Tom Watson wrote:
On Fri, 15 Jun 2007 20:26:23 -0500, dpb wrote:


The electric utilities spend a great deal on research and I spent a
sizable fraction of my career in the utilities business working w/ EPRI
(Electric Power Research Institute, a utility-funded R&D organization)
in the I&C and Transmission & Distribution areas and if the concept was
considered very high on the list, it would have received funding for at
least theoretical work. To the best of my knowledge it hasn't.


The problem with those who are educated is that they have been trained
off the obvious.

Their predilection is to assume the veracity of the precedent, without
question.

I'm asking you to revisit the fundamental assumptions.



I'm not sure where you're going with this. Skin Effect is
not an "assumption" - it can be calculated and probably even
measured. From http://en.wikipedia.org/wiki/Skin_effect we
get this (near the end of the article):


In copper, the skin depth at various frequencies is shown below.

frequency depth

60 Hz 8.57 mm
10 kHz 0.66 mm
100 kHz 0.21 mm
1 MHz 66 µm
10 MHz 21 µm


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. A possible solution to this problem consists of
using cables with multiple insulated conductors. A thin film of silver
deposited on glass is an excellent conductor at microwave frequencies.

----------------------

Note that multi-wire transmission lines for very high power shortwave
transmitters (and their attendant power supply lines) make use of this
fact today. So .... where are you going, I wonder ...


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

Tom Watson wrote:
On Fri, 15 Jun 2007 20:26:23 -0500, dpb wrote:


The electric utilities spend a great deal on research and I spent a
sizable fraction of my career in the utilities business working w/ EPRI
(Electric Power Research Institute, a utility-funded R&D organization)
in the I&C and Transmission & Distribution areas and if the concept was
considered very high on the list, it would have received funding for at
least theoretical work. To the best of my knowledge it hasn't.


The problem with those who are educated is that they have been trained
off the obvious.

Their predilection is to assume the veracity of the precedent, without
question.

I'm asking you to revisit the fundamental assumptions.


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...

--

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?

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

Tom Watson wrote:
On Fri, 15 Jun 2007 20:26:23 -0500, dpb wrote:


The electric utilities spend a great deal on research and I spent a
sizable fraction of my career in the utilities business working w/ EPRI
(Electric Power Research Institute, a utility-funded R&D organization)
in the I&C and Transmission & Distribution areas and if the concept was
considered very high on the list, it would have received funding for at
least theoretical work. To the best of my knowledge it hasn't.


The problem with those who are educated is that they have been trained
off the obvious.

Their predilection is to assume the veracity of the precedent, without
question.

I'm asking you to revisit the fundamental assumptions.



I'm not sure where you're going with this. Skin Effect is
not an "assumption" - it can be calculated and probably even
measured. From http://en.wikipedia.org/wiki/Skin_effect we
get this (near the end of the article):


In copper, the skin depth at various frequencies is shown below.

frequency depth

60 Hz 8.57 mm
10 kHz 0.66 mm
100 kHz 0.21 mm
1 MHz 66 µm
10 MHz 21 µm


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. A possible solution to this problem consists of
using cables with multiple insulated conductors. A thin film of silver
deposited on glass is an excellent conductor at microwave frequencies.

----------------------

Note that multi-wire transmission lines for very high power shortwave
transmitters (and their attendant power supply lines) make use of this
fact today. So .... where are you going, I wonder ...
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

Not with the intent of giving offence but -

That is a particularly shabby piece of reasoning.



On Fri, 15 Jun 2007 20:50:12 -0500, dpb wrote:

Tom Watson wrote:
On Fri, 15 Jun 2007 20:26:23 -0500, dpb wrote:


The electric utilities spend a great deal on research and I spent a
sizable fraction of my career in the utilities business working w/ EPRI
(Electric Power Research Institute, a utility-funded R&D organization)
in the I&C and Transmission & Distribution areas and if the concept was
considered very high on the list, it would have received funding for at
least theoretical work. To the best of my knowledge it hasn't.


The problem with those who are educated is that they have been trained
off the obvious.

Their predilection is to assume the veracity of the precedent, without
question.

I'm asking you to revisit the fundamental assumptions.


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...
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

At DC the entire volume of the conductor is carrying current, not
just the surface.
The DC resistance of a conductor is:
R = [bulk resistivity] x [length] / [cross sectional area]
In the above area is independent of geometry. It works for round,
square, triangular, etc.
If current only flowed on the surface the above equation would have
the wire circumference in it instead of area.

For AC skin depth is a factor as others have already pointed out.
Changing the geometry of the conductor, from a rod to a sheet, is
one remedy for this. Litz wire is another and it is good for up to
about 1MHz IIRC.

Art


"Tom Watson" wrote in message
...
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:
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?


Several reasons leap to mind:

1) The place where you typically most care about efficient current
conduction (i.e., where resistive losses matter especially) is in
high power applications. These typically are in the 50-60Hz
range where skin effect is negligible.

2) The complexity and cost to manufacture what you suggest was
either impossible or so economically irrational that it was
never pursued historically. Even today, with quite sophisticated
manufacturing process technologies, is it really worth it to, say,
make a better coax to go from cable converter to your TV? The
currents (and losses) involved are miniscule and almost certainly
pale by comparison to the costs to spin up a new wire manufacturing
facility.

3) In effect, what you ask for is already taking place. In high frequency
applications like VHF/UHF radios and microwave Radar, there is a
technique called "microstripline" that uses the copper etching on
a circuit board (thin but with appropriate area) to actually synthesize
discrete components like capacitors and inductors. This has been done
for years. But note: These are very high to microwave range frequencies
where skin effect does indeed kick in AND the places where microstripline
is used tends to be medium to low power environments - say under 500 watts
or so (at least that's my last recollection - things may well have changed
in the intervening eons).

4) As someone already pointed out - the Public Futilities have a deep
and vested interest in reducing cost and improving reliability of
their plants and transmission facilities. They have many
Smarty Pants Engineers (tm) who look at exactly these questions.
If/When there is a compelling economic driver to do this, you'll
see it happen. Again, though, they live at 50-60Hz so it's not
likely ...

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

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:
Or better yet with silver which not only conducts temperature better
than gold but electricity as well.

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

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?

Experimenting with light weight conductors is always being done. But
the holy grail is room temp super conductor. The skin effect does
happen but at the diameter of the conductors generally used it is not
a problem (DC current). The electrons are forced in a random pattern
similar to the way photons travel within the suns deepest layers
changing from atom to atom within the conductor, but with a very
limited area.

But as Davis Estep once told me in my beginning of my tech career,
either it is forward biased or not.

It works or it does not.

Not an EE, but a eclectic electronic technician of over 25 years.

Mark
(sixoneeight) = 618

Look up wave guides, as frequency reaches Giga hertz range the current
passes along the skin. Radar frequencies actually travel inside a hollow
conductor that "funnel" the signal from the electronic circuit output to the
antenna.


"Tom Watson" wrote in message
...
You are moving towards my theory on this, Tim.


On Fri, 15 Jun 2007 20:24:33 -0500, Tim Daneliuk
wrote:

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.?



I think this is all about frequency. At 60hz I don't believe this
buys you much, but at Mhz/Ghz freqs it might ...


Oh, in a related note ... In my misspent youth, I installed/repaired
High Frequency Single Sideband Radios for fishing boats in Alaska.

Many of these vessels were wooden and ground is rather important when
designing HF radio antennas. We could typically find good ground at the
heat exchanger in the bilge of the ship which was metal and in contact
with the ocean.

The problem always was that these are typically pretty far away (20-100
feet) from the wheelhouse. If we used wire to get to ground, that wire
then actually became a radiator of radio energy - which is not what you
want from a ground.

So, we used copper flashing which was very thin but *Wide*. At HF
frequencies, area turns out to be a big deal for ground planes. In the
worst case, we'd use 00 or even 0 welding cable to get to a real ground
because - IIRC - the effective area of a wire is something like 2-3x its
diameter.
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

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.

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

"Tom Watson" wrote in message
...
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?

I used to work in an industry that catered to the electric utility industry,
specifically in transmission and distribution. If there was ever an
industry where this would matter, this would be it. The concept of, for
lack of a better term, bimetallic cable is not foreign to this industry.
The have a variety of cables classified as ACSR (Aluminum Conductor, Steel
Reinforced). These cables contain a stranded steel core with a stranded
aluminum covering. Now, the purpose of this is not for cost reduction, but
in high-strength applications where aluminum or aluminum-alloy conductors
would not be strong enough. My assumption would be that since the engineers
are familiar with this product and its current-carrying capabilities (and
how it relates to AAC and AAAC conductors), if there was an advantage to
this sort of arrangement, they'd be doing it. From your other posts on this
thread, it appears that you think it just hasn't occurred to them to check.
That might be the case, but I doubt it.

todd

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

That is a particularly shabby piece of reasoning.

It's true, however...as someone else has noted, if it were economically
feasible, it would have been done a long time ago as the actual concept
does exist.

You, of course, in your infinite wisdom, are welcome to enter the field
and make your fortune in an area others have overlooked.

--

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.

If you teach a non creative person that x is true, he will think that
x is true.

He may pass his whole life without questioning what x is.


I've played with drummers who are like that.



Go back to the initial question and see if you can answer it.


So far, I haven't seen any satisfactory answers.








On Fri, 15 Jun 2007 21:51:09 -0500, "todd" wrote:

"Tom Watson" wrote in message
.. .
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?

I used to work in an industry that catered to the electric utility industry,
specifically in transmission and distribution. If there was ever an
industry where this would matter, this would be it. The concept of, for
lack of a better term, bimetallic cable is not foreign to this industry.
The have a variety of cables classified as ACSR (Aluminum Conductor, Steel
Reinforced). These cables contain a stranded steel core with a stranded
aluminum covering. Now, the purpose of this is not for cost reduction, but
in high-strength applications where aluminum or aluminum-alloy conductors
would not be strong enough. My assumption would be that since the engineers
are familiar with this product and its current-carrying capabilities (and
how it relates to AAC and AAAC conductors), if there was an advantage to
this sort of arrangement, they'd be doing it. From your other posts on this
thread, it appears that you think it just hasn't occurred to them to check.
That might be the case, but I doubt it.

todd

Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

ex cathedra v. non cathedra.

is this really the best that you can do?





On Fri, 15 Jun 2007 22:00:45 -0500, dpb wrote:

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

That is a particularly shabby piece of reasoning.

It's true, however...as someone else has noted, if it were economically
feasible, it would have been done a long time ago as the actual concept
does exist.

You, of course, in your infinite wisdom, are welcome to enter the field
and make your fortune in an area others have overlooked.
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

Tom Watson wrote:
ex cathedra v. non cathedra.

is this really the best that you can do?


It's really the best (actually more than) it deserves here.

--

... 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".

Tom Veatch
Wichita, KS
USA

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.

Tom Veatch
Wichita, KS
USA

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.

todd

On Jun 15, 7:43 pm, Tom Watson wrote:
[snipped for brevity]

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.

Please add some more information:

1) define 'thick' ('thickness' can be manipulated via the increase in
voltage carried.... jack up the voltage high enough, and I can push a
whack of power through a wire the size of a human hair.)
2) at what frequency, or range of frequencies?


r

Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane
mittam.

http://forums.craigslist.org/?forumID=96

You might try your question there. They really get into this kind of thing
there.

todd

"Tom Watson" wrote in message
...
ex cathedra v. non cathedra.

is this really the best that you can do?





On Fri, 15 Jun 2007 22:00:45 -0500, dpb wrote:

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

That is a particularly shabby piece of reasoning.

It's true, however...as someone else has noted, if it were economically
feasible, it would have been done a long time ago as the actual concept
does exist.

You, of course, in your infinite wisdom, are welcome to enter the field
and make your fortune in an area others have overlooked.
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

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

IIRC in 6th grade science class I learned that the energy travels on the
outside of the wire.





"Tom Watson" wrote in message
...
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/