Definition of Surface Tension

 

Quantitative definition of surface tension

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Imagine a line AB to be drawn on the free surface. The force due to surface tension acts tangential to the surface (shown F), all along the line AB, whose length is l. These forces stretch the surface to acquire minimum surface area.

Mathematically or quantitatively, surface tension (T) is the force per unit length of an imaginary line drawn on the surface of the liquid, acting perpendicular to the line and tangential to the surface.