Experimental study of viscosity and capillary flow of liquid

A water solution is allowed to flow under gravity through a horizontal capillary tube of uniform bore and small area of cross section. The molecules in contact with the wall of the capillary tube are at rest, and those along the axis of the tube flow with a maximum speed. This difference in the movement of molecules from one layer to the next inside the capillary tube resists the flow of water solution due to molecular friction of the liquid known as viscosity. The flow of water solution from one end to another of the horizontal capillary tube is due to a difference in pressure at the two ends. We perform an experiment to measure the coefficient of viscosity η and the resistance R of flow of water solutions for different concentrations c using Poiseuille’s viscosity apparatus.