JCECE Medical JCECE Medical Solved Paper-2006

  • question_answer
    If the volume of gas is changed from \[{{V}_{1}}\]to \[{{V}_{2}}\]isothermally, then work done is:

    A) \[RT\,\ln \frac{{{V}_{1}}}{{{V}_{2}}}\]

    B)  \[RT\,\ln \frac{{{V}_{2}}}{{{V}_{1}}}\]

    C)  \[R({{T}_{2}}-{{T}_{1}})ln\frac{{{V}_{2}}}{{{V}_{1}}}\]

    D)  \[R({{V}_{2}}-{{V}_{1}})ln\frac{{{T}_{2}}}{{{T}_{1}}}\]

    Correct Answer: B

    Solution :

     Key Idea: Ideal gas equation is \[PV=RT\] Work done in isothermal process is \[W=\int_{{{V}_{1}}}^{{{V}_{2}}}{p\,dV}\] From ideal gas law \[PV=\text{ }RT\] \[\therefore \] \[W=\int_{{{V}_{1}}}^{{{V}_{2}}}{\left( \frac{RT}{V} \right)}\,dV=RT\int_{{{V}_{1}}}^{{{V}_{2}}}{\frac{dV}{V}}\] \[\Rightarrow \] \[W=RT\,\ln \,\left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)\]


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