A capillary of 0.8 mm diameter is immersed in water, and rises 2 cm above the water. To what height will the water rise in it? How can the result be made consistent with the result of the previous problem?

Explanation

Water will start rising and will reach the upper end of the capillary. Here the radius of curvature will decrease until the pressure of the curved surface becomes equal to the hydrostatic pressure of the water column. Then the water will stop rising. The condition for equilibrium is
`Deltap=(2 sigma cos theta)/(r)= rho gh`
For the contact angle we obtain
`"cos" theta= (r rho gh)/(2sigma)=0.544, theta=57^(@)`