BHU PMT BHU PMT Solved Paper-2003

  • question_answer
    A monatomic gas supplied the heat Q very slowly keeping the pressure constant. The work done by the gas will be:                                                                                                                                                                [BHU M-2003]

    A)  \[\frac{2}{3}Q\]                                              

    B)  \[\frac{3}{5}Q\]

    C)  \[\frac{2}{5}Q\]                                              

    D)  \[\frac{1}{5}Q\]

    Correct Answer: C

    Solution :

                     Key Idea: Apply first law of thermodynamic In isobaric process                                                 \[Q=n{{C}_{P}}\Delta T\] Also, \[dU=n{{C}_{V}}\Delta T\]                 \[\therefore \]  \[\frac{Q}{dU}=\frac{n{{C}_{P}}\Delta T}{n{{C}_{V}}\Delta T}=\frac{{{C}_{P}}}{{{C}_{V}}}=\gamma \] For monoatomic gas, \[\gamma =\frac{5}{3}\] \[\therefore \]                  \[\frac{Q}{dU}=\frac{5}{3}\] \[\Rightarrow \]                               \[dU=\frac{3}{5}Q\] Now, form first law of thermodynamics                                                 \[Q=dU+W\]                 \[\Rightarrow \]                               \[W=Q-dU\]                                                 \[=Q-\frac{3}{5}Q\]                 \[\therefore \]                  \[W=\frac{2}{5}Q\]


You need to login to perform this action.
You will be redirected in 3 sec spinner