JEE Main & Advanced Physics Thermodynamical Processes Question Bank Self Evaluation Test - Thermodynamics

  • question_answer
    The relation between U, P and V for an ideal gas in an adiabatic process is given by relation \[U=\text{ }a+bPV.\] Find the value of adiabatic exponent \[\left( \gamma  \right)\]of this gas.

    A) \[\frac{b+1}{b}\]

    B) \[\frac{b+1}{a}\]

    C) \[\frac{a+1}{b}\]

    D) \[\frac{a}{a+b}\]

    Correct Answer: A

    Solution :

    [a] \[U=a+bPV\]                                                ?.(i) In adiabatic change, \[dU=-dW=\frac{nR}{\gamma -1}\left( {{T}_{2}}-{{T}_{1}} \right)=\frac{nR}{\gamma -1}\left( dT \right)\] \[\Rightarrow U=\int_{{}}^{{}}{dU}=\frac{nR}{\gamma -1}\int_{{}}^{{}}{dT}\] \[orU=\left( \frac{nR}{\gamma -1} \right)T+a=\frac{PV}{\gamma -1}+a\]             ?(ii) Where a is the constant of integration. Comparing (1) and (2), we get \[b=\frac{1}{\gamma -1}\Rightarrow \gamma =\frac{b+1}{b}.\]


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