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Railways NTPC (Technical Ability) Thermodynamics Question Bank Thermodynamics

  • question_answer
    The COP of a refrigerator on a reversed Carnot cycle is 5. The ratio of higher absolute temperature to the lower temperature \[(i.e.,\,\,{{T}_{2}}/{{T}_{1}})\] is:

    A) 1.25                             

    B) 1.3

    C) 1.4                               

    D) 1.2

    Correct Answer: D

    Solution :

    \[{{(COP)}_{\text{Ref}}}=\frac{{{T}_{2}}}{{{T}_{1}}-{{T}_{2}}}=\frac{1}{\frac{{{T}_{1}}}{{{T}_{2}}}-1}=5\] \[5\,\frac{{{T}_{1}}}{{{T}_{2}}}-5=1\] \[\frac{{{T}_{1}}}{{{T}_{2}}}=\frac{6}{5}=1.2\]


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