Capillary Tube
As shown in Fig. 1.9, if a small open tube is inserted into a container with water, we see that water raises into the tube. We now get a liquid-gas-solid interface. In this case, attraction or adhesion between solid and water is strong and is able to overcome the mutual cohesion between liquid molecules. That is why water rises into the tube. The liquid is said to wet the surface.
The height of the liquid column is related to surface tension,
tube radius, specific weight of the liquid and angle of contact
It is seen that if the tube radius is small the
capillary rise, h is pronounced. That is narrower the tube
more the height to which the fluid rises in it. But whether the
fluid rises in the capillary tube or not is decided by the
contact angle, (c) Aerospace, Mechanical & Mechatronic Engg. 2005 University of Sydney |