CBSE Class 11-science Answered
explain why:
- tea or coffee is sipped from a saucer when it is quite hot.
- A desert cooler cools the room in summer.
- oil rises up in the wick in an oil lamp?
Asked by Preksha | 10 Dec, 2017, 01:08: PM
Expert Answer
Tea or coffee is sipped from a saucer when it is quite hot.
When tea is poured in a saucer, it cools faster. Evaporation is a surface phenomenon.
Particles of tea on the surface absorb heat of vaporisation from the remaining particles of tea and evaporate.
Tea thus loses heat and cools faster.
A desert cooler cools the room in summer.
On a hot dry day, due to the increase in temperature, the rate of evaporation of water is more.
Also, the dryness of the air, i.e. decrease in the humidity of the air increases the rate of evaporation.
Therefore, a desert cooler cools better on a hot dry day.
Oil rises up in the wick in an oil lamp.
Oil rises up in the wick in an oil lamp due to capillary action. This effect is due to surface tension of liquids.
Capillary action is the phenomenon by which any liquid rises up in a wick.
Answered by Varsha | 11 Dec, 2017, 10:50: AM
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