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DCaD
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Join Date: Aug 2007
Location: Columbia City, Indiana, USA
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Temperature Coefficient

10/30/2013 6:01 PM

Dear Friends and Associates,

I hope you can help with my confusion. I work with magnet wire and coils, and I needed to find (again) the temperature coefficient of Copper and Aluminum. Sounded easy enough, but It seems everywhere I look, I find DIFFERENT ANSWERS. It makes no sense at all.

All these are given per degrees C (where there are extensive lists, I am choosing the one closest to the materials I am using)

Chemistry and Physics Handbook (yes, some of us DO still own books )

Cu = 0.0039 Al = 0.0039

Engineers Toolbox (http://www.engineeringtoolbox.com)

Cu = 0.00429 Al = 0.0038

(http://hyperphysics.phy-astr.gsu.edu)

Cu = 0.0068 Al = 0.00429

(http://hyperphysics.phy-astr.gsu.edu/hbase/electric/restmp.html#c3) NOTE these last two are the same 'company', but two different pages give different references.

Cu = 0.0039 Al = 0.0039

AAAARRRRRRGGGGGG!!!!!!!

What in the world to do?!?!?! It seemed like such a SIMPLE thing to search. (like the lady in the spaghetti sauce commercial, "I wonder what other stupid choices I've made before?")

If anyone has the CORRECT answer, I would appreciate knowing. (it WILL be interesting to see how many different answers I get from everyone ) And, if someone could let me know what they use and believe is a consistently reliable source of materials data.

Kind regards ...

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#1

Re: Temperature Coefficient

10/30/2013 6:13 PM

Temperature coefficient of.......?

.

If you are going to complain about the quality of information available, at least make sure enough information is provided in your complaint......

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DCaD
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#4
In reply to #1

Re: Temperature Coefficient

10/30/2013 6:58 PM

Hello Truth,

You are correct ... the issue is Temperature Coefficient of Resistivity.

Kind regard ...

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#5
In reply to #4

Re: Temperature Coefficient

10/30/2013 9:37 PM

The temperature coefficient of resistivity for copper and aluminum is pretty close to the same value.... roughly between 0.0039/°C - 0.0040/°C when close to 20°C. The coefficient will probably be different for various alloys and possibly even for different conditions of the conductor, i.e. annealed, oxygen free, under high pressure, etc.

.

I suspect the variation you noted either reflects values for various alloys, or perhaps reflects something other than a ratio per °C (perhaps Ω/°F ?).

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DCaD
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#6
In reply to #5

Re: Temperature Coefficient

10/30/2013 11:58 PM

Thanks for the information. Can you cite your source?

It's consistent with the Chemistry and Physics Handbook, which I would hope is accurate.

Thanks for your help.

Kind regards ...

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truth is not a compromise
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#7
In reply to #6

Re: Temperature Coefficient

10/31/2013 10:33 AM

Here is a decent reference for copper.

.

I'm embarrassed to say I was going off memory, and cannot find a good reference for the temperature coefficient of electrical resistivity for aluminum. Even worse, when I estimate the coefficient using data from a reliable source, the results differ from the answer I previously provided (with high confidence).

.

0.0043/°C - 0.0045/°C is probably closer to the value for aluminum... so, close, but still a little bit higher than copper.

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DCaD
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#8
In reply to #7

Re: Temperature Coefficient

10/31/2013 3:03 PM

Thanks for the data, and thanks for confirming how strangely difficult it is to find the data. I think what I'm going to do is (1) run with what seems the best data at the moment, but also (2) find a way to do my own confirmation. I think I can, and I probably won't need more than a few data points to confirm.

It's not really necessary, but I really need to find some substance to the data. My wife has a name for that behavior .

Kind regards, and thanks for your help ...

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Fredski
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#2

Re: Temperature Coefficient

10/30/2013 6:17 PM

It's not hard to track downhttp://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html
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Fredski
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#3
In reply to #2

Re: Temperature Coefficient

10/30/2013 6:19 PM

or here http://hyperphysics.phy-astr.gsu.edu/hbase/tables/thexp.html
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