Conductivity

Conductivity is the capcity of bodies to transmit heat, electricity or certain vibrations.

Metals such as gold, silver and copper have a high thermal conductivity (they conduct heat easily), whereas materials such as glass and asbestos have a much lower thermal conductivity. The latter are insulators.

Conduction is the only effective heat transfer method through opaque solids. When one of the ends of a metal bar is heated, the heat is transmitted by conduction to the other colder end. The precise mechanism of conduction in solids has still not been elucidated but it is mainly due to the movement of free electrons in the body triggered as soon as there is a difference in temperature. Thus, good heat conductors are usually good electrical conductors.

A mathematical definition of thermal conduction: in 1822, the French mathematician Joseph Fourier gave a precise mathematical definition of conduction. According to Fourier's law, the speed at which heat is conducted in a body per unit of cross section is proportional to the opposite of the body's temperature gradient. The proportionality factor is the material's thermal conductivity.

PHYSICS - The capacity of bodies to transmit heat, electricity or certain vibrations.