HEAT - POST 13

HEAT  BLOG 13

RADIATION - part 2

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In today's blog lesson we will be bringing the Chapter on HEAT to a close.  We will look into a few practical applications based on heat being transferred by Radiation and will learn through a simple experiment that the amount of heat absorbed or received by an object / body is dependent on the distance from the source of heat.

Read the activity given below :

INFERENCE  : The quantity of heat absorbed by a body depends upon its distance from the source of heat.

-The quantity of heat absorbed by a body depends on its distance from the source of heat

Now I will be asking you some questions on radiation. Try to solve them yourselves before reading the answers.

        

Click on the link below :  The clipping tells us about  black  surfaces and how  the amount of heat radiated varies.

  https://www.youtube.com/watch?v=5GoZZKcNZiQ&feature=youtu.be

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The link below explains why woollen clothes keep us warm and why wearing many layers  of clothing keeps us warmer when compared to wearing just one thick layer. ( Statement - Reason type of Questions)

https://youtu.be/poi7H4UxmXg

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DO QUESTIONS  34,35,36 ( GIVEN BELOW ) IN YOUR NOTEBOOK

Q 34)    Why does an electric room heater have a polished surface behind?

Ans) An electric room heater is provided with a curved polished reflector behind the heating element. This polished surface reflects back all the heat radiation falling on it towards the person sitting in front of the room heater.

Q 35)    Why are the    bases( bottoms) of cooking utensils painted black, whereas sides are sparkling bright?

Ans) Black bodies are good heat absorbers and bright bodies are poor heat radiators. The bottom of a cooking utensil is painted black so that it can absorb more heat and

sides are kept bright so that they do not radiate heat.

Q 36)    Why are the pipes of solar heater and containers of heat of the solar cooker painted black?

Ans) Black bodies are good absorbers of heat. The pipes and containers are painted black so that they can absorb the maximum amount of heat from the solar radiation.

Examples explained in video:-

https://youtu.be/poi7H4UxmXg

W e bring the chapter on Heat to a close.  Click on the link below and sit back and RELAX

  https://www.youtube.com/watch?v=yUEPGMnRqGs&feature=youtu.be....

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 Hw  Click on these videos for a quick recap on Radiation.

.Recap of Radiation   https://www.youtube.com/watch?v=5GoZZKcNZiQ

 &

 https://www.youtube.com/watch?v=enrsfHG5eB8

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CW  /HW - TEXT in GREEN to be written out.

DRAW THIS CHART GIVEN BELOW IN YOUR NOTEBOOK- ( Do not draw the diagrams )

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