Can Anyone explain what is the direction of Surface Tension? I studied it is along the Tangential plane to the surface e considered at the location of length element considered.. And within that plane it is Perpendicular to length element?.. In the attached Pic.. Is the reason for the direction Of surface tension right? And one more thing.. What is the relation between the surface tension and Interface? Like If there is interface of Water and Air.. WHY IS Surface tension is there..
That is not the actual reason for surface tension. We know that all the molecules attract each other which is the reason for it being a liquid. But there is a difference between the molecules on the surface and inside the liquid. The molecules inside the liquid are attracted by molecules all around it, but the molecules on the surface are only attracted by the molecules below it and so are not in equilibrium. These molecules have higher potential energy than the one inside.
These molecules on the surface interact with any other surface and try to attain a more stable state. This is the reason for surface tension. In the above example , it arises due to the interaction of the molecules of water and the container.
And if there is no container to hold water, it tries to attain the shape with least surface area as it is the shape with least energy. This is the reason why rain drops are spherical (not exactly spherical due to gravity).