A capillary tube with inner cross-section in the form of a square of side a is dipped vertically in a liquid of density `rho` and surface tension `rho` which wet the surface of capillary tube with angle of contact `theta` . The approximate height to which liquid will be raised in the tube is : (Neglect the effect of surface tension at the corners of capillary tube)

Options

A. `(2sigma cos theta)/(arhog)`
B. `(4sigma cos theta)/(arhog)`
C. `(8sigma cos theta)/(arhog)`
D. None of these

Explanation

Upward force by capilary tube on top surface of liquid is
`f_(up)=4 sigma a cos theta`
If liquid is raised to a height h then we use
`4 sigma cos theta=ha^(2) rhog` or `h=(4sigma cos theta)/(arhog)` Ans.