NEET NEET SOLVED PAPER 2015 (C)

  • question_answer
    A Carnot engine, having an efficiency of \[\eta =\frac{1}{10}\]as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is

    A)  \[100\,\text{J}\]             

    B)  \[99\text{J}\]                   

    C)         \[90\text{J}\]                   

    D)  \[1\text{J}\] 

    Correct Answer: C

    Solution :

                    As,      \[{{Q}_{1}}+W={{Q}_{2}}\] Given,         \[\eta =\frac{1}{10}\] Now, using   \[\eta =1-\frac{{{T}_{1}}}{{{T}_{2}}}\] So, \[\frac{1}{10}=1-\frac{{{T}_{1}}}{{{T}_{2}}}\] \[\Rightarrow \,\,\,\frac{{{T}_{1}}}{{{T}_{2}}}=\frac{9}{10}\] Now       \[\frac{{{Q}_{1}}}{{{Q}_{2}}}=\frac{{{T}_{1}}}{{{T}_{2}}}\]                 \[\Rightarrow \,\,\,\frac{{{Q}_{1}}}{{{Q}_{1}}+W}=\frac{9}{10}\] \[\Rightarrow \]               \[10{{Q}_{1}}\,=9{{Q}_{1}}\,+9W\]                 \[\Rightarrow \,\,\,\,\,\,{{Q}_{1}}=9W=9\times 10=90J\]


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