Railways NTPC (Technical Ability) Thermodynamics Question Bank Thermodynamics

  • question_answer
    What is the ratio of the slopes for p?v curves for an adiabatic process and an isothermal process?

    A) \[{1}/{\gamma }\;\]                               

    B) \[\gamma +1\]

    C) \[\gamma \]                               

    D) \[\frac{1}{\gamma +1}\]

    Correct Answer: C

    Solution :

    \[Adiabatic\,\,process\,\,p{{v}^{\gamma }}\,\,=\,\,c\,\,or\,\,p\,\,=\,\,\frac{c}{{{v}^{\gamma }}}\] \[Slope,\,\,\frac{dp}{dv}\,\,=\,\,c\,\left[ \,-\,\,\gamma {{v}^{\,-\,\gamma \,-\,1}} \right]\] \[\,=\,\,p{{v}^{\gamma }}\left[ \,-\,\,r{{v}^{\,-\,\gamma \,-\,1}} \right]\]   \[\,=\,\,-\,\,p\gamma {{v}^{\,-\,1}}\]      \[Isothermal\,\,process,\,\,pv\,\,=\,\,c\,\,or\,\,p\,\,=\,\,\frac{c}{v}\]  \[Slope;\,\,\frac{dp}{dv}=-\,\,c{{v}^{\,-\,2}}=-\,\,pv\times {{v}^{\,-2}}=-\,\,p{{v}^{\,-\,1}}\]             \[\frac{{{\left( {dp}/{dv}\; \right)}_{adb}}}{{{\left( {dp}/{dv}\; \right)}_{iso}}}=\frac{-\,\,p\gamma {{v}^{\,-\,1}}}{-\,\,p{{v}^{\,-\,1}}}=\gamma \]    


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