Wax is coated on the inner wall of a capillar | vedclass

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(C) The angle of contact $	heta$ is determined by the relation $\cos 	heta = \frac{T_{SA} - T_{SL}}{T_{LA}}$,where $T_{SA}$,$T_{SL}$,and $T_{LA}$ ar

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$	heta$ increases and $h$ decreases

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(C) The angle of contact $	heta$ is determined by the relation $\cos 	heta = \frac{T_{SA} - T_{SL}}{T_{LA}}$,where $T_{SA}$,$T_{SL}$,and $T_{LA}$ are the surface tensions between solid-air,solid-liquid,and liquid-air interfaces respectively.For a clean glass capillary,water wets the surface,resulting in an acute angle of contact $(	heta  0)$.When the inner wall is coated with wax,the surface becomes hydrophobic. For water on a waxy surface,the adhesive force between water and wax is weaker than the cohesive force of water. This makes the surface tension relation such that $\cos 	heta$ becomes negative.Consequently,the angle of contact $	heta$ increases to an obtuse angle $(90^{\circ} Since the capillary rise is given by $h = \frac{2T \cos 	heta}{r ho g}$,when $	heta > 90^{\circ}$,$\cos 	heta$ becomes negative,meaning the liquid level in the capillary tube falls relative to the outside level. Thus,$h$ decreases.

Wax is coated on the inner wall of a capillary tube and the tube is then dipped in water. Then,compared to the unwaxed capillary,the angle of contact $\theta$ and the height $h$ up to which water rises change. These changes are:

Similar Questions

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Three liquids of densities $\rho_1, \rho_2$ and $\rho_3$ (with $\rho_1 > \rho_2 > \rho_3$),having the same value of surface tension $T$,rise to the same height in three identical capillaries. The angles of contact $\theta_1, \theta_2$ and $\theta_3$ obey:

Water rises in a capillary tube of radius $r$ up to a height $h$. The mass of water in the capillary is $m$. What will be the mass of water that rises in a capillary of radius $\frac{r}{4}$?

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