My name is Alexander FufaeV and here I will explain the following topic:

# Wiedemann-Franz Law: How Electrical and Thermal Conductivity Are Related

## Formula

What do the formula symbols mean?

## Thermal Conductivity

Unit
Thermal conductivity is the specific thermal conductivity of the conductor, which depends on the geometry of the conductor (hence "specific"). This tells how capable a conductor is of transporting heat.

## Electrical Conductivity

Unit
Electrical conductivity is the specific electrical conductivity of the conductor, which depends on the geometry of the conductor (hence "specific"). This tells how well a conductor conducts the electric current.

## Lorenz number

Lorenz number is the constant of proportionality between the temperature and the ratio of conductivities. The unit of Lorenz number is $$\mathrm{V}^2 / \mathrm{K}^2$$.

## Temperature

Unit
Absolute temperature of the considered material.
Explanation

## Video

The Wiedemann-Franz law is an empirical relationship between the electrical conductivity $$\sigma$$ and the thermal conductivity $$\kappa$$ of a metal at constant temperature $$T$$.

Formula anchor

Here $$L$$ is the Lorenz number. It is the proportionality constant between the temperature and the ratio of the conductivities. The unit of the Lorenz number is $$\mathrm{V}^2 / \mathrm{K}^2$$.