Thermal conductivity the list of thermal conductivities. These should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper "(see: Copper in heat exchangers)", aluminium, and silver. On the other hand, materials with low thermal conductance, such as polystyrene foam and fire brick, are used in building construction or in furnaces in an effort to slow the flow of heat, i.e. for insulation purposes. The reciprocal of thermal conductivity is "thermal resistivity", usually expressed in kelvin-meters per watt (K⋅m⋅W). For a
Thermal conductivity given thickness of a material, that particular sample's "thermal resistance" and the reciprocal property, "thermal conductance", can be calculated. Unfortunately, there are differing definitions for these terms. Thermal conductivity, "k", often depends on temperature. Therefore, the definitions listed below make sense when the thermal conductivity is temperature independent. Otherwise a representative mean value has to be considered; for more, see the Equations section below. For general scientific use, "thermal conductance" is the quantity of heat that passes in unit time through a plate of "particular area and thickness" when its opposite faces differ in temperature by one kelvin. For a