Question

state and prove the wiedemann franz law​

Answer 1

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). ... The proportionality of κ/σ with temperature was discovered by Ludvig Lorenz in 1872.

Answer 2

Answer:

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). ... The proportionality of κ/σ with temperature was discovered by Ludvig Lorenz in 1872.

In this law:

Thermal Conductivity (κ) is a degree of the capacity of a material to conduct heat.

Electrical Conductivity (σ) is a degree of the capacity of a material to conduct electricity (1ρ).

Wiedemann Franz LawWiedemann-Franz Law Model

The law states that the ratio of electronic contribution of the thermal conductivity (κ) to the electrical conductivity (σ) of a metal is somewhat equivalent to the temperature (T).

κσ=LT

Here, the L is proportionality constant and it is called as the Lorenz number. The L is equal to:

L=κσT=π23(κBe)2=2.44×10−8 WΩK−2

The relationship between the thermal and electrical conductivity is based on the fact that heat and electrical movement involves freely moving electrons in the metal.

The Wiedemann-Franz law is based upon the fact that the heat and electrical transport both involve the free electrons in the metal. It also shows that with increase in particle velocity the electrical conductivity decreases and the thermal conductivity increases with the average particle velocity.

Wiedemann Franz Law Limitations

The value of Lorenz number L will not remain same for all materials.

The law don’t hold true for intermediate temperature.

The temperature decreases as both (κ) and (σ) increases in the pure metals.