0.0179 ohms for copper.
0.0184 ohms for annealed copper
Ď = R (A/l) where
Ď = electrical resistivity
R = electrical resistance of a uniform specimen
A = cross sectional area
l = length
Solve for R by multiplying both sides by l/A
R = Ď(l/A)
The cross section of the wire is pi * 1^2 mm = 3.14159 square mm = 3.14159e-6 square meters.
The length is 3 meters. So l/A = 3/3.14159e-6 = 9.5493e5
Ď for copper is 1.68e-8 so 1.68e-8 * 9.5493e5 = 1.60e-2 ohms at 20 C
But copper has a temperature coefficient (α) of 0.00386 per degree C.
So the resistance value needs to be adjusted based upon how far from 20 C the temperature is.
50 - 20 = 30 C
So 0.00386 * 30 = 0.1158 meaning that the actual resistance at 50 C will be 11.58% higher.
So 1.1158 * 0.016 = 0.0179 ohms.
If you're using annealed copper, the values for Ď and the temperature coefficient change.
Ď = 1.72e-8
α = 0.00393
Doing the math, you get
1.72e-8 * 9.5493e5 * (1 + 30 * 0.00393) = 0.0184 ohms
