AIIMS AIIMS Solved Paper-2001

  • question_answer
    In an adiabatic change, the pressure and temperature of a monoatomic gas are related with relation as\[P\alpha {{T}^{C}}\], where C is equal to:

    A) \[\frac{5}{4}\]                   

    B)        \[\frac{5}{3}\]                   

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

    D)        \[\frac{3}{5}\]

    Correct Answer: C

    Solution :

                    Key Idea: Poissons equation for adiabatic process is given by \[P{{V}^{\gamma }}=constant.\]                   For adiabatic process, Poissons equation is given by \[P{{V}^{\gamma }}=constant.\]                           ?....(1) Ideal gas relation is \[PV=RT\] \[\Rightarrow \] \[V=\frac{RT}{P}\]                                  ?...(2) From Eqs. (1) and (2), we get \[P{{\left( \frac{RT}{P} \right)}^{\gamma }}=constant\] \[\Rightarrow \]  \[\frac{{{\text{T}}^{}}}{{{\text{P}}^{\text{-1}}}}\text{=constant}\]                        ?....(3) where \[\gamma \] is ratio of specific heats of the gas. Given,           \[p\,\alpha \,{{T}^{C}}\]                         ?...(4) On comparing with Eq. (3), we have \[C=\frac{\gamma }{\gamma -1}\] For a monoatomic gas \[\gamma =\frac{5}{3}\] \[\therefore \] We have \[C=\frac{\frac{5}{3}}{\frac{5}{3}-1}=\frac{5}{2}\]


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