Question

Water rises to a height of 10 cm in a capillary tube and mercury falls to a depth of the same capillary tube. If the density of water is 1 gm/c.c and its angle of contact is $0^{\circ }$, then the ratio of such of two liquids is ( cos${135}^{\circ }$=0.7)

Answer 1

Let a liquid of density ρ rise a height h in a capillary of raduis r, then we can write

hrρg = 2Tcosθ

where T is surface tension of that liquid and θ is angle of contact.

Let Tm and Tw be the surface tension of water and mercury.

Tm/Tw = [(3.112 * 13.6)/(10 * 1)] * [cos0 / cos(135)]

θw is the angle of contact of water 0 degrees

= 5.98