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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 110\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)

  1. For the same Carnot cycle reversed: β=1−ηη\beta = \frac{1-\eta}{\eta}.
  2. β=1−1/101/10=9\beta = \frac{1 - 1/10}{1/10} = 9
  3. Heat taken from the cold reservoir: Q2=βW=9×10=90Q_2 = \beta W = 9 \times 10 = 90 J
  4. So the answer is (a) 90 J.
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