Temperature Coefficient of Resistance for Copper
The Temperature Coefficient of Resistance for Copper (near room temperature) is 0.393% per degree Celsius (C) meaning that for every 1°C rise in temperature, the resistance increases by 0.393%.
The relationship can be expressed in the formula:
R = Rref [1 + α(T – Tref)]
Where:
| R | = | Conductor resistance at temperature “T” in Ohms |
| Rref | = | Conductor resistance at reference temperature (Tref) in Ohms |
| α | = | Temperature coefficient of resistance for the conductor material |
| T | = | Conductor temperature in degrees C |
| Tref | = | Reference temp at which α is specified for the conductor material in degrees C |
Example:
Assume 100 feet of 20 gauge wire has a resistance of 1.015 Ohms at 20°C (room temp). If the temperature of the wire increases by 10°C, what will the resistance of the wire be?
R = Rref [1 + α(T – Tref)]
R = 1.015 [1 + 0.00393 (30 – 20)]
R = 1.015 [1 + 0.00393 (10)]
R = 1.015 [1 + 0.0393]
R = 1.0549 Ohms
The change in resistance (∆R) can be expressed by a simple change to the original formula:
∆R = Rref [α(T – Tref)]
Example:
Using the same assumptions as in the previous example, what will the change in the resistance of the wire be?
∆R = Rref [α(T – Tref)]
∆R = 1.015 [0.00393 (30 – 20)]
∆R = 1.015 [0.00393 (10)]
∆R = 1.015 [0.0393]
∆R = 0.0399 Ohms
The temperature coefficient of resistance for some common materials at 20°C:
- Copper = 0.00393
- Aluminum = 0.004308
- Iron = 0.005671
- Nickel = 0.005866
- Gold = 0.003715
- Tungsten = 0.004403
- Silver = 0.003819
Further details about temperature coefficients of resistance can be found on the All About Circuits web site.
A calculator is available on the University of Georgia HyperPhysics web site.