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?

Answer 1

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 ${90}^0\mathrm{or}{270}^0$.