RAJASTHAN ­ PET Rajasthan PET Solved Paper-2007

  • question_answer
    A Carnot's engine has an efficiency of 50% at sink temperature\[50{}^\circ C\]. Calculate the temperature of source.

    A) \[133{}^\circ C\]           

    B) \[143{}^\circ C\]

    C) \[100{}^\circ C\]           

    D) \[373{}^\circ C\]

    Correct Answer: D

    Solution :

     \[\eta =\frac{Net\text{ }work\text{ }done/cycle}{Total\text{ }amount\text{ }of\text{ }heat\text{ }absorbed\text{ }/\text{ }cycle}\] Or \[\eta =\frac{W}{{{Q}_{1}}}\] \[\therefore \] \[=\frac{{{Q}_{1}}-{{Q}_{2}}}{{{Q}_{1}}}\] Or \[n=1-\frac{{{Q}_{2}}}{{{Q}_{1}}}\] As \[\frac{{{Q}_{2}}}{{{Q}_{1}}}=\frac{{{T}_{2}}}{{{T}_{1}}}\] \[\therefore \] \[\eta =1-\frac{{{T}_{2}}}{{{T}_{1}}}\] ?..(i) where,\[{{T}_{2}}\]is temperature of sink and \[{{T}_{1}}\]is the temperature of the source. Here,          \[\eta =50%\] \[{{T}_{2}}=50{}^\circ C=273+50=323\text{ }K\] Putting these values in Eq. (i), we get \[\frac{50}{100}=1-\frac{323}{{{T}_{1}}}\] \[T=646K=373{}^\circ C\]


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