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Question
It is said that a liquid rises or is depressed in capillary due to the surface tension. If a liquid neither rises nor depresses in a capillary, can we conclude that the surface tension of the liquid is zero?
Solution
No, we cannot conclude the surface tension to be zero solely by the fact that the liquid neither rises nor falls in a capillary.
The height of the liquid inside a capillary tube is given by \[h = \frac{2T\cos\theta}{r\rho g}\] . From the equation, we see that the height (h) of the liquid may also be zero if the contact angle \[\theta\] between the liquid and the capillary tube is \[{90}^0 \text{ or } {270}^0\] .
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