The resistivity of an alloy of Ni is 2 x 103 Ohmm the dimens

The resistivity of an alloy of Ni is 2 x 10^-3 Ohm-m; the dimensions of a rectangular bar of this material are w = 4 mm, t = 10 mm, and I = 50 mm; the thermal conductivity of this alloy is:

The answer is: 1.47 * 10^(-8) W m^-1 K^-1

I am not sure how they arrived to this answer..

Solution

The given resistivity is electrical resistivity. By inversing electrical resistivity you can find electrical conductivity. Thermal conductivity can be related to electrical resistivity using Wiedemann–Franz law.

K/   = L*T

Where K = Thermal conductivity

= Electrical conductivity ( = 1/electrical resistivity)

L = Lorentz Number = 2.45 10^-8 W.ohm/K²

T = temperature in Degree Kelvin