Explain about the modes of heat transfer

The topic you have asked is a basic academic topic taught over decades in schools and colleges. You may read from any standard text book. This information is freely available around easily and is generic and academic.

As you've said there are three modes of transfer of heat: conduction, convection and radiation. In Condu tion, heat is transferred by the molecules inside the object. When a molecule is heated, it vibrate thus rubbing the neighbouring molecules, the heat is thus transferred to the next molecules.

Convection: This mode of heat transfer is mostly used to heat liguid and gas. When a liguid is heated, the hot liquid rises and the cold liquid sinks. When the colder liguid gets heated it rises and the cooler liquid sink. Through this process, the whole body of water gets heated.

Radiation: This mode of heat transfer does not require medium. The heat directly 'jumps' to the 'target'

There are basically three modes of heat transfer:

1. Conduction: Conduction is said to occur in solids mostly. In conduction, the solid gradually gets heated up until it reaches the temperature of the heating element.Holding a metal scale over a candle is a good example of conduction. In conduction, there is no net movement of the atoms of the metal. However, since the heat is also a form of energy, as you heat up the metal, the electrons on the metal surface start vibrating more and more violently. This results in each electron passing some of its energy to the adjacent atom and that electron starts vibrating and so on.

2. Convection: Convection is the mode of heating in liquids. Heating a pot of water on the stove is the best example of convection. Here, the heating effect is due to the actual movement of molecules. When a pot of water is held on the stove, the base of the pot becomes hot by conduction. Then, this heat is absorbed by the water molecules in contact with the surface of the pot and they then start moving about more randomly than they did before because of the increase in energy. This causes more water molecules to occupy the area they left at the base of the stove and then these get more energy. This process repeats until the water boils and gets converted into steam. Note that convection occurs by actual motion of the molecules.

3. Radiation: This form of heat transfer doesn't require any actual contact with the heat source. An example is, when we leave an iron nail in the sun, it gets heated up. But there is no contact between the sun and the nail. This is because of infra-red radiation, which is absorbed by the nail and it gets heated up. Radiation is also the prime cause for the green house effect and global warming.

Hope this was helpful

Arun

There are three modes of heat transfer they are:
1.conduction
2.convection
3.radiation
Conduction is the transfer of heat between same medium e.g solid to solid.In convection heat transfer takes place between different medium e.g solid to liquid.

Basically there are three types of modes of heat transfer-
1. Conduction
2. Convection
3. Radiation

1. Conduction - This is for transfer of heat in solid. In metallic Solid transfer of heat is due to random movement of electron. This basic phenomenon of physics , when an electron get higher energy it gets exited and reach to the higher energy level and after a short period of time the extra energy is released. Energy is always flow from higher energy level to lower energy level. Same principle is occur here. When metal surface comes in contact with heat energy the electrons got exited and their kinetic energy increases therefore they start vibrational motion and collide with adjacent electrons in this way one by one they transfer energy to the near by electrons and finally metal become hot.

2. Convection - Convection process is slightly different from Conduction . In conduction process heat itself moves across a solid surface but in Convection which is basically occurs in liquid , Liquid absorb heat from heated plate and moves through the cold liquid. When this hot liquid drops comes in contact with cold liquid drops , cold liquid become hot . In this way Convection process heat transfer very quickly.

3. Radiation - Radiation is the simplest mean of heat transfer . All matter constantly radiate energy in the form of electromagnetic radiation. Electromagnetic radiation does not require any moving atom to heat transfer. By only the mean of radiation heat can be transfer in the vacuum. This is the reason that a closed thermos bottle having vacuum in inner and outer layer become to the same temperature as surrounding.

There are three mode. 1.conduction 2.convection3.radiation conduction is occur solid to solid medium. example two plate are join together one plate heat is high temperature and other is low temperature. the heat is transer to high temperature plate to low temperatureplate.CONVECTION: It is occurs between two phases. liquid to solid. that is heat is transfer between liquid to solid or solid to liquid.RADIATIONS: Here there is no any contact on physically. only waves of heat is transfered. ex:radio waves