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Heat transfer - Coggle Diagram
Heat transfer
Conduction
The mode of transfer of heat from hotter part of a material to its colder part or from a hot material to a cold material in contact with it, without the movement of material as a whole, is known as conduction.
In all the solids, heat is
transferred by the process of conduction.
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Convection
The mode of transfer of heat from the hotter part of a fluid (liquid or gas) to its colder parts by the movement of the liquid (or gas) itself is known a convection. The transfer of heat by convection can take place only in liquids and gases. It is due to the reason that the particles in liquids and gases can move about freely.
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So, the transfer of heat by convection cannot take place in solids because the
particles in the solids are fixed at a place and cannot move about freely.
It is also not occurred in empty space or vacuum because there are no particles of of any kind in empty space which can move and transfer heat.
Convection of air
Air is a very poor conductor of heat, Air transfers heat from its hotter parts the colder parts by the process of convection.
Convection of water
Water is a poor conductor of heat. So, due to this reason, it cannot transfer
heat by conduction but it transfers heat by the process of convection.
Radiation
The mode of transfer of heat through which heat energy from a hot body to a cold body by means of heat rays without any material medium between them is
known as radiation.
E.x.
the sun’s heat reaches the earth by the process of
radiation. The sun is very far away from the earth, and there is mainly an empty space (vacuum) between the sun and the earth even, then the heat from
the sun reaches the earth. This is due to the fact that the sun being extremely
hot, emits invisible heat radiation (or infrared rays) in all directions.
Depending on the temperature of surroundings, our body too gives heat-to the surroundings or receives heat from the surroundings by radiation.
If a hot utensil filled with hot milk is kept away from the flame, then it
cools down by transferring its heat to the surroundings by radiation.
If we stand next to a burning fire, then we will feel the heat of the fire
falling on our face. The heat is transferred from the fire to our face by the
process of radiation.
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