Question

Give reasons why:
(a) Hot liquid remains hot and the cold liquid remains cold in the thermos flask.

(b) Woollen clothes are worn during the winter season.
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Answer 1

Answer:

a) Since there is vacuum between the walls of the bottle, flow of heat by convection is also ruled out. Due to the silvering of the walls heat is not lost by radiation. As a result, hot things kept in a thermos flask, do not become cold and cold ones do not become hot for a long time.

b) Since both air and wool being bad conductor of heat prevent the loss of heat prevent the loss of heat by conduction from our body to surrounding. So we feel warm in winter in woolen cloths.

Explanation:

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