Heat can be defined as the energy exchanged when a difference in temperature exist between two regions. The science of heat transfer attempts to describe the exchange of heat when the appropriate physical conditions characterizing that process have been specified. According to classical theory, there are three ways that heat can be transferred; these are by conduction, convection, and radiation.

In conductive heat transfer, heat is transported through solid materials or stagnant fluids from one body at a given temperature to another body at a lower temperature by the transfer of kinetic energy through molecular impact. In gases and liquids, where molecules are farther apart than in solids, the energy transferred by molecular collisions is smaller than in solids, where heat conduction is facilitated by atomic vibrations in the crystal. In solids that conduct electricity, heat conduction is further enhanced by the drift of free electrons...