InterviewSolution
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InterviewSolution
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A cappillary tube of radiue `r` is lowered into water whose surface tension is `alpha` and density `d`. The liquid rises to a height. Assume that the contact angle is zero. Choose the correct statement (s):A. Magnitude of work done by force of surface tension is `(4pialpha^(2))/(dg)`B. Magnitude of work done by force of surface tension is `(2pialpha^(2))/(dg)`C. Potential energy acquired by the water is `(2pialpha^(2))/(dg)`D. The amount of heat developed is `(2pialpha^(2))/(dg)` |
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Answer» Correct Answer - A::C::D `h=(2alpha)/(dgr)` hence work done by force of surrface tension is `W_(S)=alphaxx2pirxxh=(4pialpha^(2))/(dg)` But centre of mass of liquid in the capillary tube is at a hight `(h)/(2)`. Hence potential energy gained `=(Mgh)/(2)=pir^(2)xxhxxdxxgxx(h)/(2)=(2pialpha^(2))/(gd)` Hence work done by gravity `=(-(2pialpha^(2))/(dg))` Amount of heat developed `=(2pialpha^(2))/(dg)` |
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