Experiments to Demonstrate Surface Tension

Experiments to demonstrate surface tension:

(i) When a painting brush is dipped into water, its hair gets separated from each other. When the brush is taken out of water, it is observed that its hair will cling together. This is because the free surface of water films fries to contract due to surface tension.


(ii) When a sewing needle is gently placed on water surface, it floats. The water surface below the needle gets depressed slightly. The force of surface tension acts tangentially. The vertical component of the force of surface tension balances the weight of the needle.