NEET AIPMT SOLVED PAPER 2002

  • question_answer
                    The efficiency of Carnot engine is 50% and temperature of sink is 500 K. If the temperature of source is kept constant and its efficiency is to be raised to 60%, then the required temperature of the sink will be:

    A)                                                                                                                                                                            600 K    

    B)                 500 K    

    C)                 400 K 

    D)                 100 K

    Correct Answer: C

    Solution :

                      Efficiency of the Carnot engine is given by                 \[\eta =1-\frac{{{T}_{2}}}{{{T}_{1}}}....(i)\]                 where  \[{{T}_{1}}=\] temperature of source                 \[{{T}_{2}}=\]temperature of sink                 Given, \[\eta =50%\,=0.5,\,\,{{T}_{2}}=500\,K\]                 Substituting in relation (i), we have                 \[0.5=1-\frac{500}{{{T}_{1}}}\]                 or            \[\frac{500}{{{T}_{1}}}=0.5\]                 \[\therefore {{T}_{1}}=\frac{500}{0.5}=1000\,K\]                 Now, the temperature of sink is changed to \[T_{2}^{'}\] and the efficiency becomes 60% i.e., 0.6.                 Using relation (i), we get                 \[0.6=1-\frac{T_{2}^{\,'}}{1000}\]                 or            \[\frac{T_{2}^{\,'}}{1000}=1-0.6=0.4\]                 or            \[T_{2}^{\,'}=0.4\times 1000=400K\]                 Note:    Carnot engine is not a practical engine because many ideal situations have been assumed while designing this engine which can practically not be obtained.


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