At the disposal of a physicist, there are two thermal reservoirs - very hot with temperatures 22 7 ∘ C and just hot with temperatures 7 7 ∘ C . Physicist is told to run a refrigerator by extracting 20

Question

At the disposal of a physicist, there are two thermal reservoirs - very hot with temperatures $22 7^{\circ} C$ and just hot with temperatures $7 7^{\circ} C$ . Physicist is told to run a refrigerator by extracting 2000 J from just hot body. What is the minimum mechanical work he'll have to do? The heat capacities of the hot and very hot body can be considered very large.

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Answer:

A

Solution:

$\frac{Q _{Swe}}{W} = \frac{T _{L}}{T _{H} - T _{L}} = \frac{350}{150}$

$W = \frac{2000}{350} \times 150 = \frac{6000}{7} J$

TestHub · Accepted Answer

​ W Q Swe ​ ​ = T H ​ − T L ​ T L ​ ​ = 150 350 ​ ​ ​ W = 350 2000 ​ × 150 = 7 6000 ​ J

Physics - Heat & Thermo Question with Solution | TestHub

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