What is the significance of Wiedemann-Franz Lorenz law?
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].
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.
Which of the following relation gives Wiedemann-Franz law where ΣT thermal conductivity and ΣE electric conductivity *?
The WiedemannFranz law is the ratio of the electronic contribution of the thermal conductivity (k) to the electrical conductivity (σ) of a metal, and is proportional to the temperature (T). L=σTk=3π2(ekB)2=2.
What is the expression of Lorenz number its significance and value?
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.
What is the content of the Wiedemann-Franz law and for which materials does it hold?
Wiedemann-Franz law is the law which relates the thermal conductivity (κ) and the electrical conductivity (σ) of a material which consists of somewhat freely moving electrons in it. Thermal Conductivity (κ): It is the degree (measure) of capacity of a material to conduct heat.
How is Lorentz number calculated?
Because the charge carriers (electrons in n-type or holes in p-type semiconductors) transport both heat and charge, κE is commonly estimated using the measured σ using the Wiedemann-Franz law: κE = LσT, where L is the Lorenz number.
How is Lorenz number calculated?
What is meant by Lorentz number?
The Lorentz number is a dimensionless number that relates the thermal conductivity of a metal to its temperature and its electrical conductivity. The Lorentz number equals voltage squared times specific electrical conductivity divided by the temperature difference and specific thermal conductivity.
What is the cause of failure of free electron theory?
Drawbacks of classical free electron theory 1) It fails to explain the electric specific heat and the specific heat capacity of metals. 2) It fails to explain superconducting properties of metals. 3) It fails to explain new phenomena like photo-electric effect, Compton effect, Black body radiation, etc.
What is Lorentz no?
Is Lorenz number constant?
Thus, L is typically estimated either as a constant (2.44 × 10−8 WΩK−2) or by applying a transport model—such as the single parabolic band (SPB) model obtained by solving the Boltzmann transport equations—to experimental data.
What is meant by Lorenz number?
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.