Wiedemann–Franz law

The Wiedemann–Franz law states that, in metals, the ratio of thermal conductivity to electrical conductivity is proportional to absolute temperature, with the Lorenz number as proportionality constant.

Lorenz number: The ratio of a material’s thermal conductivity to its electrical conductivity and absolute temperature. It is the proportionality constant in the Wiedemann–Franz relation.
Electrical conductivity: A material property measuring how readily electric current flows under an applied electric field. It is the charge-transport quantity paired with thermal conductivity in the law.
Lorenz ratio: The ratio of thermal conductivity to electrical conductivity divided by absolute temperature. Comparing this measured ratio with the Lorenz number shows whether the law holds.
Gustav Wiedemann: A German physicist who studied the thermal and electrical properties of metals. His measurements helped establish the empirical connection between the two conductivities.
Drude model: A classical model that describes electrical and thermal transport in metals through collisions of mobile electrons. It gives an early kinetic explanation for linked electrical and thermal conduction.
Thermal conductivity: A material property measuring how readily heat flows through a temperature gradient. The law estimates its electronic contribution from electrical conductivity and temperature.
Phonon: A quantized collective vibration of atoms in a solid. Phonons carry heat without carrying electrical charge, so they can raise the measured ratio.
Rudolf Franz: A German physicist who investigated heat and electrical conduction in metals. His work with Wiedemann gave the empirical law its name.
Sommerfeld model: A quantum model of conduction in metals that applies Fermi–Dirac statistics to their electrons. It derives the law more accurately by accounting for the electrons’ quantum statistics.
Thermoelectric effect: The coupling of heat flow and electrical behavior that produces voltage from temperature differences or heat from current. Thermoelectric transport measurements test the relation among charge, heat, and temperature.

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