Heat Transfer Through Convection


 
 
Concept Explanation
 

Heat Transfer Through Convection

Convection

The transfer of heat because of movement of the molecules of the medium; via mass transfer; is called convection or convection of heat.Water and air are bad conductors of heat. But they do become hot, in spite of being bad conductors. Heat transfer in fluids takes place through convection.

Convection in Water:

When water is heated in a pan, the particles of water which are near the source of heat; get heated first. Because of heating, they become light; and rise in water. The gap which is created because of rise of hot particles is filled cold particles of water from the surrounding area. Thus a cyclical movement of particles begins and ends up heating the whole water of the pan. The cyclical movement in fluids because of heating is called convection current.

Convection in Air:

Air gets heated because of convection; the way water gets heated. Air near the source of heat gets heated and rises above. This leaves a gap; which is filled by the colder air from the surrounding. The convection current thus starts in air which results in heating up of air.

When you place your palm above a flame you will feel the hotness of the flame. But when you will place your palm below the flame the area will be colder. This shows how the colder air from below moves up; due to convection current.

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Sample Questions
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Question : 1

Which of the following are correct ?

(a) The transfer of heat because of movement of the molecules of the medium; via mass transfer; is called conduction of heat .

(b) The cyclical movement in fluids because of heating is called convection current.

(c) In winter, hotels and other building are centrally heated on the principle of convection.

Right Option : B
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Question : 2

Land and sea breezes arise due to _________________________ .

Right Option : A
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Question : 3

The transfer of heat because of movement of the molecules of the medium; via mass transfer; is called  ___________________ .

Right Option : B
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