Fourier's Law of Conduction

Fourier's law is an empirical law based on observation. It states that the rate of heat flow, dQ/dt, through a homogenous solid is directly proportional to the area, A, of the section at right angles to the direction of heat flow, and to the temperature difference along the path of heat flow, dT/dx i.e.

The proportionality ratio,

, is called thermal conductivity of the material.