AFMC AFMC Solved Paper-2011

  • question_answer
    The p-V diagram of 2 g of helium gas for a certain process A \[\to \]B is shown in the figure. What is the heat given to the gas during the process A \[\to \] B?

    A) 4p0V0                                    

    B) 6p0V0

    C) 4.5p0V0                                

    D) 2p0V0

    Correct Answer: B

    Solution :

    Change in internal energy from A to B is \[\Delta U=\frac{f}{2}\mu R\Delta T=\frac{f}{2}({{p}_{f}}{{V}_{f}}-{{p}_{i}}{{V}_{i}})\] \[=\frac{3}{2}(2{{p}_{0}}\times 2{{V}_{0}}-{{p}_{0}}\times {{V}_{0}})\] \[=\frac{9}{2}{{p}_{0}}{{V}_{0}}\] Work done in process A to B is equal to the area covered by the graph with volume axis, ie, \[{{W}_{A\to B}}=\frac{1}{2}({{p}_{0}}+2{{p}_{0}})\times (2{{V}_{0}}-{{V}_{0}})=\frac{3}{2}{{p}_{0}}{{V}_{0}}\] Hence,      \[\Delta Q=\Delta U+\Delta W\]                     \[=\frac{9}{2}{{p}_{0}}{{V}_{0}}+\frac{3}{2}{{p}_{0}}{{V}_{0}}\]                      \[=6{{p}_{0}}{{V}_{0}}\]          


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