# Frequent question: What is the ratio of thermal conductivity to electrical conductivity equal to Lorenz number?

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The Lorenz number (L) contained in the Wiedemann-Franz law represents the ratio of two kinetic parameters of electronic charge carriers: the electronic contribution to the thermal conductivity (K_el) and the electrical conductivity (sigma), , and can be expressed as LT=K_el/sigma where T is temperature.

## What is the ratio of thermal conductivity to electrical conductivity equal to?

In physics, the Wiedemann–Franz law states that the ratio of the electronic contribution of the thermal conductivity (κ) to the electrical conductivity (σ) of a metal is proportional to the temperature (T).

## What is meant by Lorenz number?

The ratio of thermal to electrical conductivity, commonly known as the Lorenz number, is the same for almost all metals at a given temperature T and takes a value around 3(kB/e)2T, where kB and e are the Boltzmann constant and electronic charge, respectively.

## How do you calculate thermal conductivity ratio?

m. W−1, where A is the cross sectional area perpendicular to the path of heat flow, and l is the thickness (length) of the conductor parallel to the heat flow. Then thermal conductivity is given as: k=lRθA. Now, we are given that the ratio of thermal conductivity of two different materials is 5:3.

## What is the relation between thermal conductivity k and electrical conductivity sigma?

The Wiedemann–Franz Law (1853) states that the ratio of the electronic contribution of the thermal conductivity κ to the electrical conductivity σ of a metal is proportional to the temperature T based on a semi-classical treatment of the electron gas [11, 24].

## Which metal has the maximum thermal conductivity?

As you can see, out of the more common metals, copper and aluminum have the highest thermal conductivity while steel and bronze have the lowest. Heat conductivity is a very important property when deciding which metal to use for a specific application.

## What is meaning of thermal conductivity?

Thermal conductivity can be defined as the rate at which heat is transferred by conduction through a unit cross-section area of a material, when a temperature gradient exits perpendicular to the area.

## What is meant by electrical conductivity?

Conductivity is the measure of the ease at which an electric charge or heat can pass through a material. A conductor is a material which gives very little resistance to the flow of an electric current or thermal energy. Materials are classified as metals, semiconductors, and insulators.

## What is the expression for Wiedemann Franz law?

The usual statement of the Wiedemann–Franz law is, Kσ=LT. Here K is the electrical component of the thermal conductivity, σ is the thermal conductivity, T is the absolute temperature, and L is the Lorentz number.

## How do you calculate lattice thermal conductivity?

By splitting the total anharmonic interatomic lattice potential into its diagonal and nondiagonal contributions, V=Vd+Vnd, the effect of the equilibrium and nonequilibrium properties of the crystal lattice on the thermal conductivity can be studied separately.

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