Answer to Question #155224 in Molecular Physics | Thermodynamics for Samir khan

Question

Describe the three forms of thermal energy transfer.

Answer 1

There are three forms of thermal energy transfer: conduction, convection and radiation.

a) Conduction is the transfer of heat as a result of the direct contact of rapidly moving atoms through a medium or from one medium to another, without movement of the media. For example, when one end of a rod is heated, the atoms vibrate faster, bump into the neighbouring atoms and start them vibrating. Therefore, the atoms conduct heat from the hot end to the cool end. But during the process, the atoms themselves do not move from one end of the rod to the other.

b) Convection is the transfer of heat by the physical movement of the heated medium itself. Convection occurs in liquids and gases but not in solids. For example, in the kettle hot water rises and cold water descends until the temperature of water becomes uniform. For the atmosphere, the good example of convection is winds, it is a result of movement of hot and cold air.

c) Radiation is a transfer of heat in the form of waves through space. The radiation is a direct result of the random movements of atoms and molecules in matter. Since these atoms and molecules are composed of charged particles, their movement results in the emission of electromagnetic radiation, which carries energy away from the surface. For example, the Sun heats our Earth by radiation.