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Two Carnot engines A and B are operated in series. Engine A receives heat from a reservoir at 600 ~K and rejects heat to a reservoir at temperature T. Engine B receives heat rejected by engine A and in turn rejects it to a reservoir at 100 ~K . If the efficiencies of the two engines A and B are represented by _A and _B respectively, then what is the value of _ A _ B

Options

  1. A12 7
  2. B12 5
  3. C5 12
  4. D7 12

Correct answer

D. 7 12

Step-by-step solution

Efficiency of engine A, n_A= T₁-T₂ T₁ and n_B= T₂-T₃ T₂ ; T₂= T₁+T₃ 2 =350 ~K or n_A n_B = 600-350 600 350-100 350 = 7 12

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