I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?

Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===

(Please note that the vast # of "e"lectrons shown in Figure B is simply to
show the path's of electrons. )

The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the cubes
were brought together to complete the circuit) how would it effect electron
flow where the cubes touch?

Thanks for your help.

AllTel - Jim Hubbard wrote:
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?

Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===

(Please note that the vast # of "e"lectrons shown in Figure B is simply to
show the path's of electrons. )

The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the cubes
were brought together to complete the circuit) how would it effect electron
flow where the cubes touch?

Thanks for your help.

Every atom in the conductor contributes an electron to the moving
herd. If you alter the cross section or shape of the conductor, the
total number of electrons taking part in the flow across any cross
section changes in proportion to the cross sectional area (with cross
section being defined as perpendicular to the local E field that
motivates the flow).

Since the current (number of electrons passing through a cross
section) has to be uniform, all around a current carrying loop, the
average velocity of the electrons must vary inversely to the cross
sectional area. If more of them are carrying a given current, they go
slower. If fewer have to carry that current, they mist move faster.

I think these rules cover all your cases.

"John Popelish" wrote in message
...
AllTel - Jim Hubbard wrote:

Since the current (number of electrons passing through a cross section)
has to be uniform, all around a current carrying loop, the average
velocity of the electrons must vary inversely to the cross sectional area.
If more of them are carrying a given current, they go slower. If fewer
have to carry that current, they mist move faster.


Before you attack this post, saying electrons can only travel at the speed
of light, that's incorrect. The electrons themselves can travel any speed,
but the voltage wave produced does travel at 300,000 kms per second.

JoeSixPack wrote:
"John Popelish" wrote in message
...

AllTel - Jim Hubbard wrote:

Since the current (number of electrons passing through a cross section)
has to be uniform, all around a current carrying loop, the average
velocity of the electrons must vary inversely to the cross sectional area.
If more of them are carrying a given current, they go slower. If fewer
have to carry that current, they must move faster.

Before you attack this post, saying electrons can only travel at the speed
of light, that's incorrect. The electrons themselves can travel any speed,
but the voltage wave produced does travel at 300,000 kms per second.

Before you attack this post for saying that electrons can travel at
any speed, keep in mind that Joe probably understands that this
includes any speed up to, but not including, the speed of light. ;-)

Thanks for helping out, Joe.

On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack"
wrote:

Before you attack this post, saying electrons can only travel at the speed
of light, that's incorrect. The electrons themselves can travel any speed,

---
No, they can only travel at speeds less than the speed of light.
---

but the voltage wave produced does travel at 300,000 kms per second.

---
It's not a "voltage" wave, it's an electromagnetic wave, and it can
only propagate at the speed of light in a vacuum.

--
John Fields
Professional Circuit Designer

John Fields wrote:

On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack"
wrote:


Before you attack this post, saying electrons can only travel at the speed
of light, that's incorrect. The electrons themselves can travel any speed,


---
No, they can only travel at speeds less than the speed of light.
---


but the voltage wave produced does travel at 300,000 kms per second.


---
It's not a "voltage" wave, it's an electromagnetic wave, and it can
only propagate at the speed of light in a vacuum.

i am glad some one is on the ball here! )


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Op [GMT+1=CET], hakte Jamie op ons in met:

John Fields wrote:

On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack"
wrote:


Before you attack this post, saying electrons can only travel at
the speed of light, that's incorrect. The electrons themselves can
travel any speed,


---
No, they can only travel at speeds less than the speed of light.
---


but the voltage wave produced does travel at 300,000 kms per second.


---
It's not a "voltage" wave, it's an electromagnetic wave, and it can
only propagate at the speed of light in a vacuum.

i am glad some one is on the ball here! )

Damn perhaps Maxwell can help us out

John Fields wrote:
No, they can only travel at speeds less than the speed of light.

wrong:
http://groups.google.com/group/sci.p...1738a7b007dc8c

On 30 Jul 2005 18:26:41 -0700, "Autymn D. C."
wrote:

John Fields wrote:
No, they can only travel at speeds less than the speed of light.

wrong:
http://groups.google.com/group/sci.p...1738a7b007dc8c

---
Wrong.

Since an electron has a rest mass, m0, and since:


m0
mr = -------------------- ,
sqrt (1 - (v²/c²))


its relativistic mass, mr, will tend toward infinity as its
velocity, v, approaches that of light, c.
--
John Fields
Professional Circuit Designer

"Autymn D. C." wrote in message
oups.com...
John Fields wrote:
No, they can only travel at speeds less than the speed of light.

wrong:
http://groups.google.com/group/sci.p...1738a7b007dc8c


We are indeed gifted to have so many brainiacs in here.

In article .com, Autymn D. C. wrote:
John Fields wrote:
No, they can only travel at speeds less than the speed of light.

wrong:
http://groups.google.com/group/sci.p...1738a7b007dc8c

I looked at it, and you're right, the posting at that URL is wrong.
here's another time wasting URL http://www.geocities.com/jasen_betts/Autymn.txt

--

Bye.
Jasen

John Fields wrote:

On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack"
wrote:

Before you attack this post, saying electrons can only travel at the speed
of light, that's incorrect. The electrons themselves can travel any speed,

---
No, they can only travel at speeds less than the speed of light.
---

but the voltage wave produced does travel at 300,000 kms per second.

---
It's not a "voltage" wave, it's an electromagnetic wave, and it can
only propagate at the speed of light in a vacuum.

Either an Electrolux or a Hoover.

;-)

--
Paul Hovnanian
------------------------------------------------------------------
APL is a write-only language. I can write programs in APL, but I
can't read any of them.
-- Roy Keir

"Paul Hovnanian P.E." wrote in message
...
John Fields wrote:

On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack"
wrote:

Before you attack this post, saying electrons can only travel at the
speed
of light, that's incorrect. The electrons themselves can travel any
speed,

---
No, they can only travel at speeds less than the speed of light.
---

but the voltage wave produced does travel at 300,000 kms per second.

---
It's not a "voltage" wave, it's an electromagnetic wave, and it can
only propagate at the speed of light in a vacuum.

Either an Electrolux or a Hoover.

;-)

--
Paul Hovnanian
------------------------------------------------------------------
APL is a write-only language. I can write programs in APL, but I
can't read any of them.
-- Roy Keir


Hey, My Dirt Devil, 2C

The house clean before it ever gets dirty....

;^)

"Paul Hovnanian P.E." wrote in message
...
John Fields wrote:

On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack"
wrote:

Before you attack this post, saying electrons can only travel at the
speed
of light, that's incorrect. The electrons themselves can travel any
speed,

---
No, they can only travel at speeds less than the speed of light.
---

but the voltage wave produced does travel at 300,000 kms per second.

---
It's not a "voltage" wave, it's an electromagnetic wave, and it can
only propagate at the speed of light in a vacuum.

Either an Electrolux or a Hoover.

;-)

--
Paul Hovnanian
------------------------------------------------------------------
APL is a write-only language. I can write programs in APL, but I
can't read any of them.
-- Roy Keir

Of course you can read APL programs- it's just that the necessary comments
are far,far longer than the program itself!

--

Don Kelly @shawcross.ca
remove the X to answer
----------------------------

In article xPMGe.110096$wr.102342@clgrps12, JoeSixPack wrote:

Before you attack this post, saying electrons can only travel at the speed
of light, that's incorrect. The electrons themselves can travel any speed,
but the voltage wave produced does travel at 300,000 kms per second.

electrons cannot exceed the speed of light in a vacuum. no physical object can.

That said the drift velocity of electrons in electric wires is rarely
more than walking speed, the signals are transmitted by the interaction
of the electrons electric fields - ie each electron pushes on its neighbours...

signals usually seem to propogate through coaxial conductors at 2/3 the
speed of light. iirc they travel no faster in any other type of conductor.

Even in fibreoptic cables the signals (photons) go slower than 300000 km/s
the ratio difference is the definition of the refractive index of the optic
material.

--

Bye.
Jasen

On 7/29/05 8:15 PM, in article ,
"AllTel - Jim Hubbard" wrote:

I am curious about what would happen to an electrical current in 2
situations.....

snip

It is not a stupid question--it is just irrelevant. Current flows in various
ways, and in almost all cases, the details of the flow is unimportant. The
"wires" can be made from metals, semimetals, hot glass, semiconductors,
ionic solutions, etc. Each has a different kind of conduction mechanism.

I have taken the probably impossible task upon myself to discourage thinking
of conduction as a flow of electrons.

Bill

"Repeating Rifle" wrote in message
...
On 7/29/05 8:15 PM, in article ,
"AllTel - Jim Hubbard" wrote:

I am curious about what would happen to an electrical current in 2
situations.....

snip

It is not a stupid question--it is just irrelevant. Current flows in
various
ways, and in almost all cases, the details of the flow is unimportant. The
"wires" can be made from metals, semimetals, hot glass, semiconductors,
ionic solutions, etc. Each has a different kind of conduction mechanism.

I have taken the probably impossible task upon myself to discourage
thinking
of conduction as a flow of electrons.

Bill



Not so impossible. I think many think of the electron as some little
microscopic BB with a negative charge. It may be more accurate to think of
the buggers as a microscopic region of space/time with properties that give
it a negative charge among other properties. It takes an enormous amount of
mass to move space/time. It is the properties that are passed along the
way. A bit of an illusion perhaps.



So yes, I agree, not a flow of electrons but a flow of energy...



Whatever that is.....



It is all speculation of course. I have never seen an electron, Have you?


I don't think we should judge the OP on the relevancy of his question, as we
have no idea why he asked it...

"AllTel - Jim Hubbard" wrote in message
...
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?


neither ... research "skin effect"


Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===

(Please note that the vast # of "e"lectrons shown in Figure B is simply to
show the path's of electrons. )

The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the
cubes
were brought together to complete the circuit) how would it effect
electron
flow where the cubes touch?

electron flow (or hole flow is you prefer to think that way) is determined
by total circuit resistance. (and applied EMF as per ohms law) decreasing
total resistance by increasing contact point surface area will result in
increased current flow if all other factors remain the same.



Thanks for your help.

"TimPerry" schreef in bericht
...

"AllTel - Jim Hubbard" wrote in message
...
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?


neither ... research "skin effect"

Most of the times this just aplies to AC (high frequency) circuits


Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===

(Please note that the vast # of "e"lectrons shown in Figure B is simply
to
show the path's of electrons. )

The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the
cubes
were brought together to complete the circuit) how would it effect
electron
flow where the cubes touch?

electron flow (or hole flow is you prefer to think that way) is determined
by total circuit resistance. (and applied EMF as per ohms law) decreasing
total resistance by increasing contact point surface area will result in
increased current flow if all other factors remain the same.



Thanks for your help.

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Alexander" Ýãñáøå óôï ìÞíõìá
...

"TimPerry" schreef in bericht
...

"AllTel - Jim Hubbard" wrote in message
...
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would
the
resulting electron paths be more like figure A or Figure B?


neither ... research "skin effect"

Most of the times this just aplies to AC (high frequency) circuits
Or of line-to-line voltage equal or above 220 kV.Therefore transmission
lines of 400 kV are always designed with a double conductor, thus to reduce
the corona discharge due to skin effect.


Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===

(Please note that the vast # of "e"lectrons shown in Figure B is simply
to
show the path's of electrons. )

The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the
cubes
were brought together to complete the circuit) how would it effect
electron
flow where the cubes touch?

electron flow (or hole flow is you prefer to think that way) is
determined
by total circuit resistance. (and applied EMF as per ohms law)
decreasing
total resistance by increasing contact point surface area will result in
increased current flow if all other factors remain the same.



Thanks for your help.

"Dimitrios Tzortzakakis" schreef in bericht
...


--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Alexander" Ýãñáøå óôï ìÞíõìá
...

"TimPerry" schreef in bericht
...

"AllTel - Jim Hubbard" wrote in message
...
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would
the
resulting electron paths be more like figure A or Figure B?


neither ... research "skin effect"

Most of the times this just aplies to AC (high frequency) circuits
Or of line-to-line voltage equal or above 220 kV.Therefore transmission
lines of 400 kV are always designed with a double conductor, thus to
reduce
the corona discharge due to skin effect.
A tranismission line always has an AC element according to fourier Analysis.
Some times it is superimposed on an DC element but nearly always you want to
avoid this.


Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===

(Please note that the vast # of "e"lectrons shown in Figure B is
simply
to
show the path's of electrons. )

The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the
cubes
were brought together to complete the circuit) how would it effect
electron
flow where the cubes touch?

electron flow (or hole flow is you prefer to think that way) is
determined
by total circuit resistance. (and applied EMF as per ohms law)
decreasing
total resistance by increasing contact point surface area will result
in
increased current flow if all other factors remain the same.



Thanks for your help.

"Dimitrios Tzortzakakis" wrote in message
...


--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Alexander" Ýãñáøå óôï ìÞíõìá
...

"TimPerry" schreef in bericht
...

"AllTel - Jim Hubbard" wrote in message
...
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would
the
resulting electron paths be more like figure A or Figure B?


neither ... research "skin effect"

Most of the times this just aplies to AC (high frequency) circuits
Or of line-to-line voltage equal or above 220 kV.Therefore transmission
lines of 400 kV are always designed with a double conductor, thus to
reduce
the corona discharge due to skin effect.

Oh boy, you have a 'couple of crossed wires' there.

"Skin effect" is the phenomenon where electric current flow is forced out
from the center of a conductor due to the self-inductance in the conductor
when carrying AC current. The higher the frequency, the more pronounced the
current shift to the exterior. It's mostly a problem with high current
situations, even if the voltages are so low that corona discharge is not a
problem.

"Corona discharge" is *NOT* caused by AC or skin effect. Corona discharge
is caused by a high voltage gradient in the space around a conductor. This
is a combination of the voltage applied to the conductor and the effective
radius of the conductor. A high voltage, or very small effective radius can
increase the gradient to the point where the air is ionized. Simple proof
is that corona discharge is a problem with high DC voltage systems as well
as AC.

Sometimes hollow tubes are used for high frequency power conductors. This
reduces the weight and cost by eliminating the central part of the
conductor, where 'skin effect' has rendered the impedence high anyway. So
little admittance is lost for a great savings in material/weight.

And for high voltage systems, multiple parallel conductors are used to give
a larger 'effective radius', thereby reducing the corona losses.

But the two phenomenon are not related, and the two techniques used are not
really related.

daestrom

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "daestrom" Ýãñáøå óôï ìÞíõìá
...

"Dimitrios Tzortzakakis" wrote in message
...


--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Alexander" Ýãñáøå óôï ìÞíõìá
...

"TimPerry" schreef in bericht
...

"AllTel - Jim Hubbard" wrote in message
...
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would
the
resulting electron paths be more like figure A or Figure B?


neither ... research "skin effect"

Most of the times this just aplies to AC (high frequency) circuits
Or of line-to-line voltage equal or above 220 kV.Therefore transmission
lines of 400 kV are always designed with a double conductor, thus to
reduce
the corona discharge due to skin effect.

Oh boy, you have a 'couple of crossed wires' there.

"Skin effect" is the phenomenon where electric current flow is forced out
from the center of a conductor due to the self-inductance in the conductor
when carrying AC current. The higher the frequency, the more pronounced
the
current shift to the exterior. It's mostly a problem with high current
situations, even if the voltages are so low that corona discharge is not a
problem.

"Corona discharge" is *NOT* caused by AC or skin effect. Corona discharge
is caused by a high voltage gradient in the space around a conductor.
This
is a combination of the voltage applied to the conductor and the effective
radius of the conductor. A high voltage, or very small effective radius
can
increase the gradient to the point where the air is ionized. Simple proof
is that corona discharge is a problem with high DC voltage systems as well
as AC.

Sometimes hollow tubes are used for high frequency power conductors. This
reduces the weight and cost by eliminating the central part of the
conductor, where 'skin effect' has rendered the impedence high anyway. So
little admittance is lost for a great savings in material/weight.

And for high voltage systems, multiple parallel conductors are used to
give
a larger 'effective radius', thereby reducing the corona losses.

But the two phenomenon are not related, and the two techniques used are
not
really related.

Yes, but also in voltages =15 kV there's a signifigant skin effect, that's
why all transmission conductors are constructed with a steel *core* and an
*aluminium* outer sheath, because the current tends to flow on the skin of
the conductor.I mentioned corona discharge, to bring into evidence the very
strong electric field around the conductor in very high voltages.
daestrom

On Sat, 30 Jul 2005 02:14:28 -0400, "TimPerry"
wrote:


"AllTel - Jim Hubbard" wrote in message
.. .
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?


neither

---
That's not true. The electrons diffusing through the flattened
portion of the wire would result in a charge flow profile more like
Figure B, given the understanding that none of the electrons would
follow a straight-line path through any portion of the wire.
Further, the assumption is made that the cross-sectional area of the
wire remains constant at the connection.
---


... research "skin effect"

---
To what end? Skin effect comes into play when the current in the
wire is alternating.
--

Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===



--
John Fields
Professional Circuit Designer

In article , TimPerry wrote:

"AllTel - Jim Hubbard" wrote in message
...
I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed
electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?


neither ... research "skin effect"

AIUI the skin effect is for AC (and other time-varying signals)

In a uniform conductor carrying a constant DC the current will be uniformly
distributed.

in the hammered flat sections it will be mostly uniform:
the centre part of each flat provides a slightly shorter
path and therefore possibly a slightly lower resistance.
On the other hand the hammering of the copper will increase
its resistivity more where it's most deformed (this is the
centre part of the flat) so that may tend to counteract the
shortest path effect...

Bye.
Jasen

On Fri, 29 Jul 2005 23:15:20 -0400, "AllTel - Jim Hubbard"
wrote:

I am curious about what would happen to an electrical current in 2
situations.....

Assume that you have 2 wires that, when joined, complete a closed electrical
DC circuit with electrons flowing thusly.....

------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============


If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?

Figure A

--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===


Figure B

--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===

(Please note that the vast # of "e"lectrons shown in Figure B is simply to
show the path's of electrons. )

The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the cubes
were brought together to complete the circuit) how would it effect electron
flow where the cubes touch?

Thanks for your help.



For DC or low-frequency AC, charge flow will be uniform across the
cross-section of a round wire conductor (or, actually, any shaped
conductor with unchanging cross-section.) If you butt two clean-cut
wires against each other, they're now effectively a single wire, so
current distribution is still uniform.

The cube situation is more complex. A wire pokes a nearly uniform
circle of current into the cubes, and the other wire (by symmetry)
sucks it up uniformly across its cross-section, but the current
spreads out as it passes through the large cube, most diffuse halfway
through and necking down near the entry/exit circles at the wires. The
exact current distribution within the cube is complex, usually
computed using finite-element simulation. It might be possible to use
calculus to compute this distribution, but I wouldn't want to try.

At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."

John

On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

John

On Sat, 30 Jul 2005 10:50:24 -0700, John Larkin
wrote:

On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

---
I would think that simple thermal effects would cause charge to flow
closer to the surface just because that part of the conductor would
be cooler, ergo lower resistance than the hotter interior.

--
John Fields
Professional Circuit Designer

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "John Fields" ?????? ??? ??????
...
On Sat, 30 Jul 2005 10:50:24 -0700, John Larkin
wrote:

On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

---
I would think that simple thermal effects would cause charge to flow
closer to the surface just because that part of the conductor would
be cooler, ergo lower resistance than the hotter interior.
That can happen in high impulse short circuit currents.An unfused 220 V
circuit shortcircuited between live and earth, can have an impulse current
of 20 kA.Properly fused with a circuit breaker, up to 50 A.In normal
operating conditions, a transmission line of 150 kV operating at 200 A with
an ambient teperature of 20 deg.C (65deg.F)should not exceed 50
deg.C(105deg.F)however as it operates continually at these conditions the
temperature is uniform across the conductor (ACSR).

John Fields wrote:

I would think that simple thermal effects would cause charge to flow
closer to the surface just because that part of the conductor would
be cooler, ergo lower resistance than the hotter interior.


To which Tzortzakakis Dimitrios replied:

That can happen in high impulse short circuit currents.An unfused
220 V
circuit shortcircuited between live and earth, can have an impulse
current
of 20 kA.Properly fused with a circuit breaker, up to 50 A.In normal
operating conditions, a transmission line of 150 kV operating at 200
A with
an ambient teperature of 20 deg.C (65deg.F)should not exceed 50
deg.C(105deg.F)however as it operates continually at these
conditions the
temperature is uniform across the conductor (ACSR).

---
I think you misunderstood my point, which was that the copper at the
surface of the conductor would, by virtue of radiation and
convection, be cooler than the copper at the center of the
conductor. Such being the case, the resistance of the cooler copper
at the surface would be less than the resistance of the copper in
the core, leading to a non-uniform radial current gradient in the
conductor.

--
John Fields
Professional Circuit Designer

"John Fields" wrote in message
...
On Sat, 30 Jul 2005 10:50:24 -0700, John Larkin
wrote:

On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

---
I would think that simple thermal effects would cause charge to flow
closer to the surface just because that part of the conductor would
be cooler, ergo lower resistance than the hotter interior.


An interesting point. *IF* the current density is uniform across the
conductor, then the heat generated would be uniform in each unit
cross-section. And a uniform heat generation in a cylindrical rod leads to
a parabolic temperature profile, the highest exactly at the centerline,
dropping of as you move outward along any radial line.

Of course, in an AC line, the current density isn't uniform, so neither is
the heat generation. So when it comes to skin effect, it tends to lower the
peak, centerline temperature.

Now, given that both copper and aluminum are excellent heat conductors, it
might be interesting to calculate how big a temperature profile could be
expected, and from this calculate the variation in resistivity.

I suspect the work has been done before, and that the difference is rather
modest for all but the largest cylindrical conductors.

daestrom

--
John Fields
Professional Circuit Designer

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "John Larkin" ?????? ???
?????? ...
On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

Very high AC currents are much more common.The output of a moderate 300 MW
alternator is 10 kA at 21 kV.A nuclear power station alternator with a
voltage of 27 kV almost reaches 20kA, with a nominal power output of 1500
MVA.Always talking about balanced three-phase systems.The output of the 300
MW power-station at 400 kV transmission voltage is just 400 A.Conductors in
all LV circuits are made of electroletically purified solid copper, 99,99 %
Cu.In MV, HV and EHV distribution and transimission voltages respectively,
they use ACSR conductors (Aluminium Conductor Steel Reinforced)that have a
steel core, but an aluminium outer sheath.

"Dimitrios Tzortzakakis" schreef in bericht
...


--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "John Larkin" ?????? ???
?????? ...
On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

Very high AC currents are much more common.The output of a moderate 300 MW
alternator is 10 kA at 21 kV.A nuclear power station alternator with a
voltage of 27 kV almost reaches 20kA, with a nominal power output of 1500
MVA.Always talking about balanced three-phase systems.The output of the
300
MW power-station at 400 kV transmission voltage is just 400 A.Conductors
in
all LV circuits are made of electroletically purified solid copper, 99,99
%
Cu.In MV, HV and EHV distribution and transimission voltages respectively,
they use ACSR conductors (Aluminium Conductor Steel Reinforced)that have a
steel core, but an aluminium outer sheath.

Sometimes you have something like Aluminium inside (for the weight) and
Cupper on the outside for conductivity. Due to the Skin Effect this is where
the most (AC) current will flow.
On some application I have even seen Cu on the inside and Au on the outside,
my guess there is at least one other material between the two for obvious
reasons.

Alexander (ACE, Applied Communications Engineer)

On Mon, 1 Aug 2005 18:23:25 +0200, "Alexander"
wrote:


Sometimes you have something like Aluminium inside (for the weight) and
Cupper on the outside for conductivity. Due to the Skin Effect this is where
the most (AC) current will flow.
On some application I have even seen Cu on the inside and Au on the outside,
my guess there is at least one other material between the two for obvious
reasons.

Really? The reasoning for that layering doesn't seem obvious to me,
so would you mind explaining it in greater detail?

--
John Fields
Professional Circuit Designer

"Dimitrios Tzortzakakis" wrote in message
...


--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "John Larkin" ?????? ???
?????? ...
On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

Very high AC currents are much more common.The output of a moderate 300 MW
alternator is 10 kA at 21 kV.A nuclear power station alternator with a
voltage of 27 kV almost reaches 20kA, with a nominal power output of 1500
MVA.

Yes, but most of the phase conductors that I've seen from large alternators
(500MW to 1200MW) to the step-up transformers are not simple round
conductors. In fact, rectangular tubing is used for the conductors (at
least those used in many nuclear stations). The tube is encased within an
outer 'pipe' and H2 is forced down the center of the tube to the end, where
it exits the tube and returns outside the tube within the outer pipe. Such
'isophase busses' are specifically designed to carry this large amount of
current just far enough to reach the main step-up transformer where it rises
from the nominal 25kv to 345kv or higher. The secondary is connected with
'normal' ACRS conductor to the remaining switch yard equipment.

daestrom

Thanks to everyone for the great input!

Hi

I just want to remind u sth. When we say: electrons flow & flow like
this & flow like this in that direction & .... It's nothing except
what a "model" is saying, a model that has matched the experiment
results in the best & most convincing way. But who can be sure that
this model matches the truth - I mean the real mechanism- as well as
experiment results. However, I don't claim it is empty of truth (in
fact, any model that is completely empty of truth can't continue even
for a short time, believe it or not).
Well, I don't mind to make u disappointed, simply want to say: BE
CAREFUL not to mix up the "model" of what happens with what
"exactly" happens.

Now experts can answer ur question based on different models, I just
wanted to remind sth that was likely to be forgotten.

--adn