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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?
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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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