Chapter 4 HEAT answer the questions.
04. Give reasons:
a.Cooking utensils are provided with wooden or plastic handles.
b. mercury level in clinical thermometer does not fall when removed from the mouth
cwoolen clothes kep us warm during winters.
d.Air in the room gets heated when the room heater kept in the corner of the room is switched on
e. Wall of the solar cooker is painted black from inside
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Answer:
1- Cooking utensils are provided with wooden or plastic handles because they do not pass heat through it......
2- A clinical thermometer measures the max temp of the human body due to the expansion of the mercury in the bulb, which flows past a kink in the column and rises in the graduated stem, to read the highest body-temp. Once it is removed from the body, the mercury stays at that level, and does not fall because it cannot flow back into the bulb -- the kink prevents the back flow. It has to be shaken vigorously, as you know, for us to get the mercury back; then it is ready to take the temp again..
Also, the temp cannot rise further on its own from the max reading because the mercury does not expand the moment the thermometer is taken out of the body.
Incidentally, temp can be measured under the armpits and in the rectum also .
3-The absorption of water internally and the non-wicking structure means that wool keeps you warm even when drenched (sailors of the north atlantic would never have survived a winter without woolen clothes). The reson why wool keps us warm is due the air pockets between fibers of wool.
4-Air in the room gets heated when the room heater kept in the corner of the room is switched on because the room heater keeps your room hot ....
5- Wall of the solar cooker is painted black from inside because if it is painted white then when it burns its became black... so it was made black coloured before only..