RAJASTHAN PMT Rajasthan - PMT Solved Paper-2004

  • question_answer
    In isothermal process, the work done in expansion of gas from volume \[{{V}_{1}}\] to \[{{V}_{2}}\] will be:

    A)  \[nRT\,\ln \left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)\]                       

    B)  \[nRT\,\left( \ln \frac{{{V}_{1}}}{{{V}_{2}}} \right)\]

    C)  \[nRT\]               

    D)         none of these

    Correct Answer: A

    Solution :

    The work done in expansion of gas from volume \[{{V}_{1}}\] to \[{{V}_{2}}\] is \[W=\int_{{{V}_{1}}}^{{{V}_{2}}}{PdV}\]                                               ...(i) Gas equation is \[PV=nRT\]                                                         ...(ii) From equations (i) and (ii) \[W=\int_{{{V}_{1}}}^{{{V}_{2}}}{\frac{nRT}{V}dV=nRT\int_{{{V}_{1}}}^{{{V}_{2}}}{\frac{dV}{V}}}\] \[=nRT\,\log \left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)\] \[\therefore \]\[W=nRT\,In\left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)\]


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