Question

Two coaxial glass tube forming an annulus with small gap are immersed in water in a trough. The inner and outer radii of the annulus are ri and ro respectively. What is the capillary rise of water in the aannulus if is the surface tension of water in contact with air?

Answer 1

Explanation:

•Capillary rise (or depression) in a tube can be calculated by making a force balance.•The force due to surface tension (liquid-solid pull), Fs=cosd•The force opposing the surface tension is the weight of the vertical-sided column of liquid of height, Fg=gh (/4)d 2•Since Fg= Fs, therefore gdhcos4