HEAT- POST -9
HEAT - Post 9
CONVECTION - Post -I
Now children,in the last class we discussed about conduction, today we will be learning a new concept of heat transfer and that is convection. You may be wondering what convection is all about….
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Click on the following link to learn about convection in water :
Convection is nothing but the transfer of heat from the hotter to the colder part of an object by the actual movement of hot particles (molecules).
One important thing to remember about convection is that , that it only takes place in liquids and gases. Solids cannot transfer heat through convection because their constituent particles cannot leave their positions.
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How does convection occur in a room ? Click on the link below:
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The cyclic movement of water or air due to heating is called convection currents. To understand the concept of convection current perform a little activity:-
Take a small crystal of potassium per manganate into a round bottomed flask containing cold water. Heat the water near the crystal with a small Bunsen burner flame. Observe the motion of the purple coloured solution. It rises from the place of heating, moves towards the top and then after some time gain moves to the point of heating. This is the same experiment in the video.
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Now the first question that will come to mind is why did the water in the flask move in this manner?
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- Water near the bottom of the flask gets heated first .
- Warm water is lighter than the surrounding cold water and hence rises to the top of the flask.
- The cold water from the surroundings moves to the bottom, gets heated up, becomes lighter and rises.
- While the water is getting heated up at the bottom of the flask,the warm water that rose a little while ago before becomes cold,
- So when the cold water which becomes warm rises up , the warm water at the top now becomes cold and heavy so it comes back to the bottom of the flask.
This cyclic movement repeats itself till the time that the water in the flask attains a uniform temperature.
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WRITTEN WORK
Q. 22 a. Define Convection : The mode of heat transfer in which the actual cyclical movement o hot and cold particles takes place.
b. convention current- The cyclic movement of water or air due to heating is called convection currents.
Q23. Why can solids not tranfer heat by convection?
ans: Solids cannot transfer heat by convection because the constituent particles cannot leave their positions.
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CW : TEXT in green to be Written out.
LO : Defines Convection
Explains concept of Convection in a liquid.
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