When a capillary tube is immersed vertically in mercury, the level of mercury in the capillary is observed to be depressed. This is due to –

Explanation

This is explaied in terms of cohesive and adhesive forces. The attractive forces in the molecules of the same substance are called cohesive forces while those in the molecules of different substances are called adhesive forces. In case of mercury, the cohesive force the stronger than the adhesive forces. As a result mercury gets detached from the glass surface and its level therefore, goes down in the capacillary tube.