EAMCET Medical EAMCET Medical Solved Paper-2004

  • question_answer
    Three samples of the same gas, X, Y and Z, for which the ratio of specific heat \[\gamma =\frac{3}{2},\] have initially the same volume. The volumes of each sample is doubled, by adiabatic process in the case of X, by isobaric process in the case of Y and by isothermal process in the case of Z. If the initial pressures of the samples X,Y and Z are in the ratio, then the ratio of their final pressures is:

    A)                  2 : 1 : 1                                

    B)                  1 : 1 : 1

    C)                  1 : 2 : 1                                

    D)                  1 : 1 : 2

    Correct Answer: B

    Solution :

                     Given: \[{{V}_{2}}=2V,\]and\[\gamma =3/2\]                 For the case of adiabatic process and for sample X, we have                 \[P{{V}^{\gamma }}=cons\tan t\]                 Hence,                  \[{{P}_{1}}V_{1}^{\gamma }={{P}_{2}}V_{2}^{\gamma }\]                 \[{{({{P}_{2}})}_{x}}={{\left( \frac{{{V}_{1}}}{{{V}_{2}}} \right)}^{\gamma }}{{P}_{1}}={{\left( \frac{{{V}_{1}}}{2{{V}_{1}}} \right)}^{\gamma }}{{P}_{1}}\]                 \[={{\left( \frac{1}{2} \right)}^{3/2}}{{P}_{1}}=\frac{({{P}_{1}})X}{2\sqrt{2}}\]                 For the case of isobaric process in which pressure remains constant and so, for sample Y                 \[{{({{P}_{2}})}_{\gamma }}={{({{P}_{1}})}_{\gamma }}\]                                               ?(ii)                 For the case of isothermal process and for sample Z                 PV =RT= constant                 Hence,                  \[{{P}_{1}}{{V}_{1}}={{P}_{2}}{{V}_{2}}\]                 \[{{({{P}_{2}})}_{z}}=\left( \frac{{{V}_{1}}}{{{V}_{2}}} \right){{P}_{1}}=\left( \frac{{{V}_{1}}}{2{{V}_{1}}} \right){{P}_{1}}=\frac{{{({{P}_{1}})}_{z}}}{2}\]     ?(iii)                 Let the ratio of initial pressure according X, Y, Z sample be                 \[2\sqrt{2}:1:2=k\]                 \[\therefore \]  \[{{({{P}_{1}})}_{X}}=2\sqrt{2}k\]and \[{{({{P}_{1}})}_{\gamma }}=k\]    and                 \[{{({{P}_{1}})}_{z}}=2k\]                  Now, putting the values of\[{{({{P}_{1}})}_{X}},{{({{P}_{1}})}_{Y}},({{P}_{1}})Z\] and \[{{({{P}_{1}})}_{2}}\]in Eqs. (i), (ii) and (iii) respectively, wg get                 \[{{({{P}_{2}})}_{X}}=\frac{2\sqrt{2}k}{2\sqrt{2}}=k\]                                      ?(iv)                 \[{{({{P}_{2}})}_{Y}}=k\]                                                                ?(v)                 \[{{({{P}_{2}})}_{Z}}=\frac{2k}{2}=k\]                                                      ?(vi)                 Therefore, from above Eqs. (iv), (v) and (vi) it is quite clear them \[{{({{P}_{2}})}_{X}}:{{({{P}_{2}})}_{\gamma }}:{{({{P}_{2}})}_{Z}}=k:k:k=1:1:1\]


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