Table of Contents
Capillarity
The Latin word capilla means hair. A tube of very fine (hair-like) bore is called a capillary tube.
When a capillary tube of glass open at both ends is dipped in liquid which wets its walls (e.g., water, alcohol), the liquid rises in the tube. But when the capillary tube is dipped in a liquid which does not wet its walls (e.g., mercury), the level of liquid is depressed in the tube.
The phenomenon of rise or fall of a liquid in a capillary tube in comparison to the surrounding is called capillarity.
Some examples of capillarity from daily life:
(i) A blotting paper soaks ink by capillary action. The pores of blotting paper act as capillaries.
(ii) Oil rises in the long narrow spaces between the threads of a wick, the narrow spaces act as capillary tubes.
(iii) We use towels made of a coarse cloth for drying our skin after taking bath.
(iv) Sap rises from the roots of a plant to its leaves and branches due to capillarity action.
(v) The tip of the nib of a pen is split to provide capillary action for the ink to rise.