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BCECE Engineering BCECE Engineering Solved Paper-2012

  • question_answer
    The angle of contact between glass and water is \[{{0}^{o}}\] and it rises in a capillary upto 6 cm when its surface tension is 70 dyne/cm. Another liquid of surface tension 140 dyne/cm, angle of contact \[{{60}^{o}}\] and relative density 2 will rise in the same capillary by

    A)  3 cm     

    B)         16 cm

    C)  12 cm                  

    D)         24 cm

    Correct Answer: A

    Solution :

                    Rise in capillary, \[h=\frac{2T\cos \theta }{rdg}\]                 \[\therefore \]  \[\frac{{{h}_{2}}}{{{h}_{1}}}=\frac{{{T}_{2}}}{{{T}_{1}}}\times \frac{\cos {{\theta }_{2}}}{\cos {{\theta }_{1}}}\times \frac{{{d}_{1}}}{{{d}_{2}}}\times \frac{{{r}_{1}}}{{{r}_{2}}}\]                                 \[\frac{{{h}_{2}}}{{{h}_{1}}}=\frac{140}{70}\times \frac{\cos {{60}^{o}}}{\cos {{0}^{o}}}\times \frac{1}{2}\times 1\]                                 \[{{h}_{2}}=\frac{{{h}_{1}}}{2}=3\,cm\]


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