Transfer of heat energy resulting from differences in temperature between adjacent bodies or adjacent parts of a body.
In the absence of a heat pump , the energy will flow from a region of higher temperature to a region of lower temperature. The transfer of energy occurs as a result of collision among the particles of the matter involved. The rate of transfer of energy is proportional to the cross-sectional area of contact and to the difference in temperature between the two regions. A substance of high thermal conductivity, such as copper, is a good thermal conductor ; one with low thermal conductivity, such as wood, is a poor thermal conductor. See also convection , radiation .