AMU Medical AMU Solved Paper-1996

  • question_answer
    A Carnots reversible engine converts 1/6 of heat input into work. When the temperature of the sink is reduced by 62 K. The efficiency of Carnots cycle becomes 1/3. The temperatures of the source and the sink, in degree Kelvin, are respectively

    A)  372, 310         

    B)  472, 410

    C)  310, 372         

    D)  744, 682

    Correct Answer: A

    Solution :

    : In first case, \[\eta =1-\frac{{{T}_{2}}}{{{T}_{1}}}=\frac{output}{input}\] \[\therefore \] \[\frac{1}{6}=1-\frac{{{T}_{2}}}{{{T}_{1}}}\] \[\therefore \] \[\frac{{{T}_{2}}}{{{T}_{1}}}=1-\frac{1}{6}=\frac{5}{6}\]or\[{{T}_{1}}=\frac{6}{5}{{T}_{2}}=1.2{{T}_{2}}\]?(i) In second case, \[\eta =1-\frac{{{T}_{2}}-62}{{{T}_{1}}};\] \[\frac{1}{3}=1-\frac{{{T}_{2}}-62}{{{T}_{1}}}\] \[\frac{{{T}_{2}}-62}{{{T}_{1}}}=1-\frac{1}{3}=\frac{2}{3};\] \[\frac{({{T}_{2}}-62)}{1.2{{T}_{2}}}=\frac{2}{3}\] or \[3{{T}_{2}}-186=2.4{{T}_{2}}\] or \[0.6{{T}_{2}}=186\] or \[{{T}_{2}}=\frac{186}{0.6}=310\,K\] Hence \[{{T}_{1}}=1.2{{T}_{2}}=1.2\times 310=372\text{ }K\] Source\[=372\text{ }K\] Sink\[=310\text{ }K\].


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