What is Thomson Coefficient (σ)

The amount of heat energy absorbed or evolved when one-ampere current flows for one second (one coulomb) in a metal between two points which differ in temperature by 1 0C  is called Thomson coefficient (σ). It is denoted by σ. Its unit is volt per 0C.

The Thomson coefficient (σ), is positive (negative) for materials exhibiting the positive (negative) Thomson effect.