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NEET 2017 · Heat Engines, Refrigerators & Second Law

Heat Engines, Refrigerators & Second Law question from NEET 2017

Q64NEET 2017Medium

Heat Engines, Refrigerators & Second Law

A carnot engine having an efficiency of $\frac{1}{10}$ as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is

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Answer: (a)

For the same Carnot cycle reversed: $\beta = \frac{1-\eta}{\eta}$ .
$\beta = \frac{1 - 1/10}{1/10} = 9$
Heat taken from the cold reservoir: $Q_2 = \beta W = 9 \times 10 = 90$ J
So the answer is (a) 90 J.

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