Question

A long capillary tube of radius of $0.2mm$ is placed vertically inside a beaker of water. If the surface tension of water is $7.2\times {10}^{-2}N/m$ and the angle of contact between glass and water is zero, then determine the height of the water column in the tube.

• A. $3cm$
• B. $9cm$
• C. $7cm$
• D. $5cm$

Answer 1

The correct option is C $7cm$

The height $h$ through which a liquid will rise in a capillary tube of radius $r$ is given by

$h=\frac{2S\cos \theta }{r\rho g}$, where $S$ is the surface tension, $\rho$ is the density of the liquid and $\theta$ is the angle of contact.

$\Rightarrow h=\frac{2\times 7.2\times {10}^{-2}\times 1}{(0.2\times {10}^{-3})\times {10}^3\times 10}=7.2\times {10}^{-2}m=7.2cm\approx 7cm$