Question

Two capillary tubes are dipped vertically in water contained in a trough. The first tube is of radius 0.2 mm. The difference in capillary rise in the two tubes is 3.6cm. Then the radius of the second tube is ( surface tension of the water=0.07N/m, g=10)

Answer 1

72 dynes/cm

The surface tension of water is 72 dynes/cm at 25°C . It would take a force of 72 dynes to break a surface film of water 1 cm long. The surface tension of water decreases significantly with temperature as shown in the graph. The surface tension arises from the polar nature of the water molecule.