Title 1.4 Surface tension.pdf ✅

Unit 1 1.4 Surface Tension


Surface Tension on Liquid Droplet • Consider a small spherical droplet of a liquid of radius ‘r’ . On the entire surface of the droplet, the tensile force due to surface tension will be acting σ = Surface tension of the liquid P = Pressure intensity inside the droplet (in excess of the outside pressure intensity)) d = Dia. of droplet. Let the droplet is cut into two halves. The forces acting on one half (say left half) will be (i) tensile force due to surface tension acting around the circumference of the cut portion and this is equal to = σ x Circumference = σ x πd (ii) Pressure force on the area π 4 d 2 = p x π 4 d 2 These two forces will be equal and opposite under equilibrium conditions σ x πd = p x π 4 d 2 p = 4σ d