Transmission Of Heat

 

"Heat energy always flows from a body of high temperature to a body of low temperature."

➡This flow of heat energy between the bodies  takes place in 3 different process:

1. Conduction

2. Convection

3. Radiation

➡Flow of heat energy between the bodies takes place until it reaches the thermal equilibrium.

1. Conduction

➡Conduction a process in which heat energy flows from one molecule to another molecule without the actual movement of the particles. 

➡Here the molecules upon attaining heat energy start vibrating at greater amplitude without change in its position and transfers the energy gained into the nearby molecules.

➡Solid mainly undergo the process of conduction.

➡Example: Heating of one end of an iron rod, there by transfer of heat energy between the molecules takes place without the movement of the molecules,the other end of the iron rod which is cold, becomes hot.

2. Convection

➡Convection is a process in which transfer of heat energy takes place between one molecule to another molecule by the actual movement of the molecules.

➡Transfer of heat energy is always vertically upwards in the process of convection.

➡The molecules which is near to the surface becomes Less dense on absorbing heat energy, so it Rises up which is called a convection current.

➡Liquids and gases are mainly goes under the process of convection.

➡The convection current continues until the entire liquid or gases aquires the same temperature.

➡Heat energy through Convection is not done in vacuum.

3. Radiation

➡Radiation is the process in which heat energy directly passes from one body to another body without the involvement of the medium.

➡Heat transfer through the process of radiation is also takes place in vacuum.

➡Transfer of heat energy by the process of radiation is called Radiant heat or the thermal radiation.

➡Radiant Heat travels in all directions.

➡Radiant Heat travels in a straight lines with the velocity of light and can also passes through vacuum.

➡Radiant heat obey the laws of reflection.

➡The material through which radiant Heat passes do not heat the material.