Elctrical Resistivities & Temperature Coefficients

The following table is taken from IEC 60287-1-1:2006 and other sources:

DescriptionSymbolResistivity ohm.m at 20 °CTemperature Coefficient 1/K at 20 °CVolumetric Heat Capacity
Aluminium Tape ArmourATA2.84E-080.004032.5E-12
Aluminium Tube ArmourAT2.84E-080.004032.5E-12
Aluminium Wire ArmourAWA2.84E-080.004032.5E-12
Cuponal (15%)Cuponal2.65E-080.004012.64E-12
Stainless SteelSS7E-0703.8E-12
Steel Wire ArmourSWA1.38E-070.0043.8E-12




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Ei Le Dec 12, 2018 6:45 PM
Correct that resistivity in given table is the DC resistivity in https://mycableengineering.com/knowledge-base/conductor-resistance ?

Should it be Ω/m as resistivity is proportional to length?  

How to calculate α20 when temperature in cable is changing? Possible to assumed it's constant in temperature range og 20-90 degrees celcius?
Steven McFadyen Dec 12, 2018 7:35 PM
The values are the ones you should use for d.c. resistivity and the units are Ω.m.  

For 20 to 90°C, normally people would assume α is constant.  Using a more accurate value is probably not going to make much difference (unless you are doing laboratory type experiments).

If you are interested in how α varies with temperature, an Internet search will give more information.
Ei Le Dec 12, 2018 7:52 PM
Great, thank you!