NEET AIPMT SOLVED PAPER 1998

  • question_answer
                    If the ratio of specific heat of a gas at constant pressure to that at constant volume is \[\gamma \], the change in internal energy of a mass of gas when the volume changes from V to 2V at constant pressure P is:

    A)                 \[\frac{R}{(\gamma -1)}\]

    B)                 P V

    C)                 \[\frac{P\,V}{(\gamma -1)}\]

    D)                                            \[\frac{\gamma \,PV}{(\gamma -1)}\]

    Correct Answer: C

    Solution :

                    Change in internal energy is                 \[\Delta U=\frac{1}{(\gamma -1)}({{P}_{2}}{{V}_{2}}-{{P}_{1}}{{V}_{1}})\]                 Here,     \[{{V}_{1}}=V,\,{{V}_{2}}=2V\]                 \[\therefore \Delta U=\frac{1}{\gamma -1}[P\times 2V-P\times V]\]                 \[=\frac{1}{\gamma -1}\times PV\]                 \[=\frac{PV}{\gamma -1}\]                 Note:    The internal energy of an ideal gas depends only on its absolute temperature (T) and is directly proportional to T.


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