CMC Medical CMC-Medical VELLORE Solved Paper-2014

  • question_answer
    The coefficient of volumetric expansion of mercury is \[18\times {{10}^{-5}}\text{/}{}^\circ C\]. A thermometre bulb has value of \[{{10}^{-6}}{{m}^{3}}\] and cross-section of stem is \[0.002\,c{{m}^{2}}\] assuming the bulb is tilled mercury at\[{}^\circ C\]. The length of mercury at \[100{}^\circ C\] is

    A)  18 cm                  

    B)  4.5 cm

    C)  2.25 cm                               

    D)  9 cm

    Correct Answer: D

    Solution :

                    The coefficient of volumetric expansion \[\gamma =18\times {{10}^{-5}}\,{}^\circ C\] \[V={{10}^{-6}}{{m}^{3}}\] Area of cross-section A \[0.002\times c{{m}^{2}}=2\times {{10}^{-7}}{{m}^{2}}\] Initial temperature\[={{T}_{1}}=0{}^\circ C\] Final temperature \[={{T}_{2}}=100{}^\circ C\] The final volume is \[V=V\,[1+\gamma \,({{t}_{2}}-{{t}_{1}})]\] \[={{10}^{-6}}[1+18\times {{10}^{-5}}(100-10)]\] \[V=1.018\times {{10}^{-6}}\] Change in volume is \[\Delta V=A\times \Delta I=V-V\]        \[=2\times {{10}^{-7}}\times \Delta I\]        \[=1.018\times {{10}^{-6}}-{{10}^{6}}\]                 \[2\times {{10}^{7}}\times \Delta I=0.018\times {{10}^{-6}}\] \[\Delta I=9\,cm\]


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