# Conductivity



## Radman (Apr 25, 2006)

No response required, simply do the poll! After a while I'll put up the answer if nobody else felt like explaining it before I get to it. This one's fairly easy too.


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## Radman (May 4, 2006)

All right, now who can back up their answers? (Oh and FYI the 100& should be 100% that was a typo.)


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## kingfisher1 (May 4, 2006)

I guessed rather the google it, but it seems to me that copper was a pretty darn good conductor yet some of the energy put in had to turned into heat (second law of tehrmodynamics?) so 89% seemed logical...


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## Radman (May 4, 2006)

This brings up a good point I forgot to mention, these answers may be slightly rounded or approximate.


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## Mayhem (May 4, 2006)

Have not taken the time to look it up but I have a strange recollection that aluminium was originally considered the ideal conductor of electricity but since that copper is a much more efficient conductor it has a rating of 100%. In saying that, it is quite likely that I am wrong.

However, given that I do recall that it was given a 100% conductivity rating in the standards, there must be some reason why resistance isn’t considered. 

Then again, given that you can never expect to transfer energy with out some form of loss (why we have never been able to achieve perpetual motion), the 100% rating may come from the fact that it has the lowest resistance of other conductors and is therefore used as the bench mark.

Suppose I should really go and find a reference to back this up. Perhaps I will do so over the weekend, unless someone else beats me to it (hint hint).


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## Chris15 (May 5, 2006)

Mayhem said:


> Have not taken the time to look it up but I have a strange recollection that aluminium was originally considered the ideal conductor of electricity but since that copper is a much more efficient conductor it has a rating of 100%. In saying that, it is quite likely that I am wrong.
> 
> However, given that I do recall that it was given a 100% conductivity rating in the standards, there must be some reason why resistance isn’t considered.
> 
> ...



I thought that gold was a better conductor than copper... and Aluminium is used for HV transmission lines around a steel core for strength.


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## Mayhem (May 5, 2006)

Chris15 said:


> I thought that gold was a better conductor than copper... and Aluminium is used for HV transmission lines around a steel core for strength.



Neither gold or aluminium are as good at conducting electricity as copper. Gold is used because it does not corrode. Aluminium is used over copper in some applications because it is stronger. Brass is used for the same reason.


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## Chris15 (May 5, 2006)

If I consult my SI Data Book, copper has aconductivity of 57.9. There is one element with better conductivity, that being silver, with a conductivity of 60. The unit is MS/m. 1 MS/m = 1 / (1 micro ohm * 1 metre) = 1 / 0.01 micro ohm centimetres. (


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## Radman (May 6, 2006)

Answer: Number 2


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## Chris15 (May 6, 2006)

I would tend to think that copper is not 100% conductive, else it would not have any resistance at all, and we know that it is not true. Superconductors are the only instance of practically zero resistance, and then only at temperatures within few degrees of absolute zero.


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## Radman (May 6, 2006)

Chris15 said:


> I would tend to think that copper is not 100% conductive, else it would not have any resistance at all, and we know that it is not true. Superconductors are the only instance of practically zero resistance, and then only at temperatures within few degrees of absolute zero.


This may explain the discrepencies: Conductivity


It says specifically of intrest

> ...conductivity values are often reported as percent IACS. IACS is an acronym for International Annealed Copper Standard or the material that was used to make traditional copper-wire . The conductivity of the annealed copper (5.8108 x 107S/m) is defined to be 100% IACS at 20°C. All other conductivity values are related back to this conductivity of annealed copper.



So I suppose this may be what Belden was referring to on that exam. (That was a rephrasal of a question off their Belden Cable College "Cable 101" Exam.)


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## Radman (May 7, 2006)

Chris15 said:


> I would tend to think that copper is not 100% conductive, else it would not have any resistance at all, and we know that it is not true. Superconductors are the only instance of practically zero resistance, and then only at temperatures within few degrees of absolute zero.



Just noticed that you haven't even voted!


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## Chris15 (May 8, 2006)

Radman said:


> Just noticed that you haven't even voted!



Correct. Is there a problem with that?  But I guess if the standard against which conductivity is measured is copper, then I guess it would be 100%. Then silver would have a conductivity of 104%! I have issues with the question (like percent of what) and I know that you have taken it from elsewhere, so I will not blame you for it, but I am withholding my vote at this point.


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## kingfisher1 (May 17, 2006)

It seems to me that 100% is measure agaist copper, makiing copper not the most conductive things around but the bench mark to which everything else is compared. is a bit like tempature. O degrees Celsius isn't an absense of a quantity. temputrue is jsut a scale that compares one things heat to anothers heat (in celius' case it being water)


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