Answer :
Final answer:
Water does not overflow from a capillary tube shorter than the rise height due to capillary action, which is influenced by surface tension and adhesion. These forces balance with gravity to maintain the water level.
Explanation:
When water rises to a height h in a capillary tube and the length of the capillary tube above the water surface is made less than h, water does not overflow due to capillary action. This action is a result of the balance between cohesive and adhesive forces. In the case of water in a glass capillary tube, adhesive forces between the water molecules and the glass are stronger than the cohesive forces between the water molecules themselves, creating an upward force that enables water to rise and maintain its level below the top of the tube even when the tube's length is shorter than the rise height.
Capillary rise is also influenced by surface tension, which helps to maintain the stability of the water column against gravity. This phenomenon is noted by the fact that the contact angle for water in a glass tube is less than 90°, leading to an upward force which is responsible for the rise. Therefore, water does not overflow because the forces of surface tension and the strength of adhesion to the glass walls of the tube counteract the force of gravity up to a certain limit described by the height h.
