BCECE Engineering BCECE Engineering Solved Paper-2001

  • question_answer
    A monoatomic gas \[(\gamma =5/3)\] at pressure P is suddenly compressed to \[\frac{1}{8}\]th of its volume adiabatically, the pressure of gas is :

    A)  \[\frac{43}{3}P\]                             

    B)  \[8P\]                  

    C) \[32P\]                

    D)                        \[\frac{24}{5}P\]

    Correct Answer: C

    Solution :

    The condition that must be obeyed by an ideal gas in an adiabatic process is given by \[P{{V}^{\gamma }}=\text{constant}\] or                            \[{{P}_{1}}{{V}_{1}}^{\gamma }={{p}_{2}}{{V}_{2}}^{\gamma }\] or                            \[{{P}_{2}}={{P}_{1}}{{\left( \frac{{{V}_{1}}}{{{V}_{2}}} \right)}^{\gamma }}\] Here,     \[{{P}_{1}}=P,\frac{{{V}_{2}}}{{{V}_{1}}}=\frac{1}{8},\gamma =\frac{5}{3}\] \[\therefore \]  \[{{P}_{2}}=P{{(8)}^{5/3}}\] or            \[{{P}_{2}}=P{{({{2}^{3}})}^{5/3}}=32\,P\] Note: The equation \[P{{V}^{\gamma }}=\]constant can be written in terms of other pair of thermodynamic variables by combining it with the ideal gas law\[(PV=nRT).\]In doing so, we will find that, \[T{{V}^{\gamma -1}}=\]constant and \[{{T}^{\gamma }}{{P}^{1-\gamma }}=\text{constant}\text{.}\]


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