Question

The thermal conductivity of copper at 300 K is 470 W/m/K. Calculate the

electrical conductivity of copper at 300K. Lorentz number L= 2.45 x 10-8​

Answer 1

Given:

Thermal conductivity of copper = 400 W/m/K

Temperature = 300 K

L = 2.45 × $10^{-8}$ ( Lorentz number)

To Find:

Electrical conductivity of copper at 300K =?

Solution:

According to Wiedemann-Franz Law, thermal conductivity and electrical conductivity are related; their relation can be represented as follow:

  $\dfrac{K}{\sigma}$  =  LT

where k = thermal conductivity in W/m/K

           T = temperature in kelvin

           L = Lorentz number

           $\sigma$ = electrical conductivity

Now, we have the value of thermal conductivity, temperature and Lorentz number, so we can easily calculate the electrical conductivity,

   $\sigma$ = $\dfrac{K}{LT}$

     = $\dfrac{400}{2.5 \times 10^{-8} }$

     = $1.6 \times 10^{10} \Omega^{-1}m^{-1}$

Hence, the electrical conductivity of copper is $1.6 \times 10^{10} \Omega^{-1}m^{-1}$