BCECE Engineering BCECE Engineering Solved Paper-2001

  • question_answer
    An ideal Carnot engine whose efficiency is 40% receives heat at 500 K. If the efficiency is to be 50% the intake temperature for this same exhaust temperature is :

    A)  600 K                                   

    B)  800 K                   

    C)  900 K                   

    D)         1000 K

    Correct Answer: A

    Solution :

    The efficiency of a C are not engine operating between temperatures \[{{T}_{1}}\]and \[{{T}_{2}}\]is given by \[\eta -1-\frac{{{T}_{2}}}{{{T}_{1}}}\] where  \[{{T}_{1}}=\]source temperature \[{{T}_{2}}=\]sink temperature In 1st case: \[\frac{40}{100}=1-\frac{{{T}_{2}}}{500}\]                 or            \[\frac{{{T}_{2}}}{500}=1-0.4=0.6\]                 or            \[{{T}_{2}}=0.6\times 500=300\,K\]                 In 2nd case: \[\frac{50}{100}\,=1-\frac{300}{T_{1}^{}}\] or            \[\frac{300}{T_{1}^{}}\,=1-0.5\,=0.5\] or            \[T_{1}^{}\,=\frac{300}{0.5}=600\,K\] Note: The efficiency of Carnot reversible engine is independent of the working substance and depends only on the absolute temperatures of the sink and the source.


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