# Transfer of thermal energy

If two bodies at different temperatures  are facing each other or are in contact, heat energy flows from a body at a higher temperature to a body at a lower temperature.

Energy will always try to flow from areas at high temperatures to areas at low temperatures. This is called thermal transfer. Thermal energy can be transferred in three main ways:

• conduction

• convection

 Conduction Convection Radiation 1 Material medium is necessary for this process Material medium is necessary for this process No material medium is required 2 It is not possible in vacuum It is not possible in vacuum It is possible in vacuum 3 The molecules of the medium do not leave their mean positions but they transfer heat as a result of vibration about their mean position The molecules of the medium move. Thus there is a mass movement of the medium. Medium does not play any role 4 The transfer of heat can be in any direction along any path The transfer of heat takes place in a vertically upward direction The transfer of heat is in all directions along a straight line path in the form of electromagnetic waves 5 This process is slow The process is faster tan the conduction The process is faster and the transfer of heat takes place with the speed of light i.e., $3\times 10^{8}ms^{-1}$