Contents
By learning Physics Topics, we can gain a deeper appreciation for the natural world and our place in it.
Differences Between Conduction, Convection and Radiation
Different Mechanisms of Heat Transfer
When two bodies having different temperatures are brought in contact with each other, heat flows from the hotter body to the colder one. Again, when there is a temperature difference between different points of a body, heat flows in the body from the point of higher temperature to the point of lower temperature.
Flow of heat from one place to another is called transmission of heat.
Heat is transmitted in three different processes:
- conduction,
- convection and
- radiation.
1. Conduction It is the process in which heat energy is transmitted from a hotter region to a colder region of a material without any displacement of molecules. Conduction usually takes place in solids. When one end of an iron rod is placed in fire, the other end becomes so hot that it becomes difficult to hold that end with our hand. In this case heat gets transmitted through the rod from the end held in fire to the other end. This is known as heat conduction.
2. Convection: It is the process in which heat is transmitted from a hotter region to a colder region of a material by the actual movement of heated molecules. This happens only in fluids i.e., in liquids and gases because here molecules can move freely. If we take some liquid in a container and heat it from below, the top part of the liquid gets heated mainly through convection.
3. Radiation: This is the process in which heat is transferred from one place to another in the form of electro-magnetic radiation in the absence of any material medium or without heating a material medium if it is present between the two places. Heat from the sun reaches the earth by radiation.
Comparison among the three modes of transmission of heat
Conduction | Convention | Radiation |
1. Material medium is required. | 1. Material medium is required. | 1. Material medium is not necessary. |
2. Molecules of the medium do not change their places during heat transmission. | 2. Molecules move to transmit heat. | 2. Since no material medium is necessary, molecular movement is not relevant even if a medium is present. |
3. Slow process. | 3. Slow process. | 3. Very fast process, heat flows at the speed of light. (3 x 108 m-s-1). |
4. Heat can travel along a straight or a curved path. | 4. Heat can travel along a straight or a curved path. | 4. Heat always travels in a straight path. |
5. Material medium gets heated. | 5. Material medium gets heated. | 5. Material medium, if present, is not heated. |