Question

An earthen pitcher used in summer cools water in it essentially by evaporation of water from
its porous surface. If a pitcher carries 4 kg of water and the rate of evaporation is 20 g per hour,
temperature of water in it decreases by AT in two hours. The value of AT is close to (ratio of
latent of evaporation to specific heat of water is 540 °C)
A. 2.7°C
B. 4.2°C
C. 5.4°C
D. 10.8 °C​

Answer 1

Answer:

Option (C) 5.4°C

Explanation:

In 2 hours, the mass of water evaporated $=2\times 20=40$ g

If the latent heat of evaporation is L then the heat taken out by of the 40 g of evaporated water

$Q=\frac{40}{1000}\times L$

$\implies Q=\frac{L}{25}$

This will be equal to the heat lost by 4 kg of water

If the specific heat of water is c then the heat lost by water

$Q=mc\Delta T$

$\implies Q=4\times c\times \Delta T$

Since both the heats will be equal

Therefore,

$\frac{L}{25}=4c\Delta T$

$\implies \Delta T=\frac{L}{25\times 4c}$

But given that

$\frac{L}{c}=540^\circ C$

Therefore,

$\Delta T=\frac{540}{100}$

$\implies \Delta T=5.4^\circ$

Hope this answer is helpful.

Know more:

Q: Explain why water remains cool in the earthen pots ?

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Q: Indian style of cooling drinking water is to keep it in a pitcher having Porous walls water comes to the outer surface very slowly and evaporates most of the energy needed for evaporation is taken from the water itself and the water is cool down assume that a pitcher contains 10 kg of water and 0.2 gram of water comes out for per second assuming no backward heat transfer from the atmosphere to the water calculate the time in which the temperature decreases by 5 degree Celsius.

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Q: How does the water kept in an earthen pot ( matka) become cool during summer?

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Answer 2

Answer:

I hope this helps u.....