wire conductivity

At 60 Hz in copper, the skin depth is about 8.5 mm, slightly thicker than gauge 0. You are talking about skin effect which is only starts to show above a few kilohertz, otherwise the raw diameter of the wire is what carries the current. Multi-strand wire (such as power cords, or speaker wire) is convenient as it flexes, but it carries no more current than an equivalent solid core wire at frequencies under around 10kHz. For transmission towers where the outer diameter of the wire is much larger that 8.5mm dia, then uses multi-stranded wire to get around it.

If you are comparing wire coated with aluminum vs a copper wire of the same diameter as the coated, then yes, the plain copper would conduct more current.

Of course corrosion will show up as a problem at connection points, but rarely does it matter for regular wire. Battery leakage though was a big problem with electronics designed in the 70s to 90s - but that mostly affect circuit boards and the connectors to them. Battery and salt are factors for wire corrosion in vehicles.

Interesting. Thanks. The results probably depend on the hardness of your water...

Indeed, have a good day!

John :-#)#

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(Please post followups or tech inquiries to the USENET newsgroup) 
John's  Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 

In the words of the prophet: Yabbut!! (Yes, but!)

Most discussions around wire material and types wind up, at least at some point, around speaker wire discussions. Hence the reference to surface area being an advantage. Speaker wires commonly carry in the multi-kHz frequencies.

For normal household use the difference will be negligible, and in some specific conditions actually favor solid conductors. And to be a tiny bit snarky: "There is a formula for that".

My specific choice for speaker wire is #12 19-strand THHN wire chucked and twisted in a drill for easier handling. Quite manageable and extremely tough.

Peter Wieck Melrose Park, PA

Yup. But, my recollection is that the "surfaces" of the individual wire strands are almost irrelevant for speaker wire. The strands are packed together, and are in frequent-enough electrical contact with one another that they behave electrically in a way very close to that of a solid wire. You don't get an additional "skin effect" conductivity win from the individual "skins" of the individual strands.

So, high-audio-frequency performance tends to be influenced more by the bulk inductance of the cable than by the solid/stranded issue. Using four conductors in a "four-cross" confirmation can help with this.

Sounds like a good economical choice.

they just flip out

electrical current, here 12v+ DC in an auto primary wire does not seek the least obstructive path that is at the interface of copper n aluminum cladding ?

Shouldn't that be CROSS-SECTIONAL area?

Yes, but actually, I think the conductivity is better with FEWER strands of thicker wire. Many strands of tiny wire ends up being a lot of air and not so much copper.

As for the original poster, that silvery coating on typical stranded wire is tin or solder, NOT aluminum. It is there mostly to make the wire solderable, but also acts as a corrosion inhibitor.

The only aluminum wire is used as power lead-ins to houses, as it is much cheaper than copper. They did use aluminum wire INSIDE houses in the US around 1966-1968, and it burned a lot of houses down, due to the cold flow of aluminum weakening the contact force.

Jon

I got some wire of 16 and 12 guage to use for 12 volt power wiring. It may have been called speaker wire. A red and black pair. The wire turned out to be aluminuim with a coating of copper.

I have seen some coax where the center conductor is aluminum with a coating of copper, but this is for use at radio frequencies where the skin effect is very much in effect.

** Yes, stranded wire is far more flexible.

** Aluminium wire is often coated in copper, not the other way around.

It improves conductivity and most importantly makes it possible to solder the ends.

Sometimes it is passed off as being pure copper to the unwary.

.... Phil

accessed the specs via 4 lines of ID codes.....copper inside, aluminum coating outside, 25 strands Ga 12 has a mil spec rating

difficult scraping the silver off with a new utility blade

** Kindly post in plain English - not pure gibberish like the above.

I have never heard of Aluminium clad Copper wire and neither has Google.

Where have you ?

.... Phil

** Copper clad aluminium wire ( aka CCA ) is commonly used for loudspeaker voice coils - enamel coated of course.

The advantage is lower weight compared to pure copper, leading to more dBs per watt.

.... Phil

s per watt. "

Depends on the application, the advantage might be negligible. The mass wil l certainly matter more at higher frequencies, so these big massive cones o n speakers in sound reinforcement bass bins might not benefit quite so much as say a woofer in a decent quality two way home speaker.

I also have heard of copper clad aluminum wire for other purposes and usual ly it is to save money. One instance it is wires strung from telephone pole s. Alot of that is copper clad steel for the tensile strength, again becaus e of cost but not just the cost of the copper, they can put up longer spans and have to set less poles.

I can't think of much reason for aluminum clad copper.

A quantity of aluminum tineed or clad (?) Material online but not specifically answering my question beyond the general rules of surface conduction.

An absence, in a brief surface read, led to a conclusion there's not a serious difference tween copper m aluminum clad copper. An original patent sez there is a layer of silver molecules between...in 1956, WE.

And the advantage is the AL clad wire is less reactive to insulation at higher temps.

Last question: when soldered is the joint as conductive as copper solder copper ?

Silver melts streams off solder joins copper copper with a low % aluminum.

I used the new aluminum clad wire giving a less conductive result but there are other available reasons for the result so a redo. Maybe a direct conparison.

Is there a potential problem with clad wire in temperature extremes? Will the layers shed in extreme (-40C) cold or heat (100C)? Or is that not extreme enough?

Just asking...

John

no, in the 1930's rubber insulation decayed against copper so cladding was produced. Aluminum cladding ( I read this last night ) did not adhere to co pper but the Westinghouse patent covering copper with silver produced a fun ctioning AL outer layer .....for lower temps on the surface or greater resi stance to degradation from outside heat sources...I'm not sure which or bot h.

Thus, with a fine multiple strand wire there is more conductivity, less deg radation more flex with a smaller space occupation. Maybe more effective bu ndling ?

that's what the material suggests. I read the answer to my question of not flowing thru less resistance toward the center of a copper wire with a thic ker AL cladding as the outer areas of conductivity are geometrically larger supplying more free electrons in this Cu AL apparently topping more conduc tive copper below.

now tell me why that wire is more resistive ? as per common knowledge.

** So what? If make no odds then makers use plain copper.

JBL have been using aluminium wire on their instrument speakers for many decades to increase efficiency. CCA is easier to work with and solder.

.... Phil

It's mostly a function of cross-section area at DC. As frequency rises and skin effect begins to be important, surface area starts to matter, so more, finer strands might be better, *but only if the individual strands are insulated from each other*.

Isaac

ISTR that the problem was mostly that electricians couldn't be bothered to learn the new techniques and so on that were mandatory to install the stuff safely. It was only when it was installed just like Cu that it was prone to overheating.

Isaac

explain cross section electron availability for an aluminum/silver/copper wire or aluminum/copper where cladding cross section is thin ?