JEE Main & Advanced AIEEE Solved Paper-2013

  • question_answer
    Assume that a drop of liquid evaporates by decrease in its surface energy. So that its temperature remains unchanged. What should be the minimum radius of the drop for this to be possible? The surface tension is T, density of liquid is\[\rho \]and L is its latent heat of vaporization.     AIEEE Solevd Paper-2013

    A) \[\frac{\rho L}{T}\]                         

    B)        \[\sqrt{\frac{T}{\rho L}}\]            

    C)        \[\frac{T}{\rho L}\]                         

    D)        \[\frac{2T}{\rho L}\]

    Correct Answer: D

    Solution :

    Surface energy of the drop \[=(4\pi {{R}^{2}})T\] Let\[(\delta m)\]mass evaporate. \[(\delta m)L=8\pi R.\text{ }\delta RT\] \[m=\rho \frac{4}{3}\pi {{R}^{3}}\]\[\Rightarrow \]\[\frac{\delta m}{\delta R}=4\pi {{R}^{2}}\rho \] \[\therefore \] \[\rho 4\pi {{R}^{2}}L=8\pi R.T\] \[\Rightarrow \] \[R=\frac{2T}{L\rho }\]


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