Uttarakhand PMT Uttarakhand PMT Solved Paper-2005

  • question_answer
    The coefficient of volumetric expansion of   mercury   is\[18\times {{10}^{-5}}{{/}^{0}}C.\]   A thermometer bulb has value of\[{{10}^{-6}}{{m}^{3}}\]and crossectional of stem is \[0.002\text{ }c{{m}^{2}}\]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 :

     Here: The coefficient of volumetric expansion \[\gamma =18\times {{10}^{-5}}/{}^\circ C\] Initial volume \[V={{10}^{-6}}{{m}^{3}}\] Area of cross section A \[=0.002c{{m}^{2}}=2\times {{10}^{-7}}{{m}^{2}}\] Initial temperature \[{{T}_{1}}=0{}^\circ C\] Final temperature \[{{T}_{2}}=100{}^\circ C\] The final volume is \[V=V[1+({{T}_{2}}-{{T}_{2}})]\] \[={{10}^{-6}}[1+18\times {{10}^{-5}}(100-0)]\] and   \[V=1.018\times {{10}^{-6}}\] Change in volume is \[\Delta V=A\times \Delta l=V-V\] or         \[=2\times {{10}^{-7}}\times \Delta l\] \[=1.018\times {{10}^{-6}}-{{10}^{6}}\] \[2\times {{10}^{-7}}\times \Delta l=0.018\times {{10}^{-6}}\] Hence,\[\Delta l=\frac{0.018\times {{10}^{-6}}}{2\times {{10}^{-7}}}=0.09\,m=9\,cm\]


You need to login to perform this action.
You will be redirected in 3 sec spinner