The angle between tangent to the liquid surface at the point of contact and solid surface inside the liquid is termed as angle of contact. It is denoted by θ. It is different at interfaces of different pairs of liquids and solids. The value of θ determines whether a liquid will spread on the surface of a solid or it will form droplets on it. For example, water forms droplets on lotus leaf as shown in figure a while spreads over a clean plastic plate as shown in figure b.
Here we consider the three interracial tensions at all the three interfaces, liquid-air, solid-air and solid-liquid denoted by Sla, Ssa & Ssl respectively as given in figure (a) and (b). At the line of contact, the surface forces between the three media must be in equilibrium. From the figure b the following relation is derived.
Sla cos θ + Ssl = Ssa
The angle of contact is an obtuse angle if Ssl > Sla as in the case of water-leaf interface while it is an acute angle if Ssl < style="font-weight: bold; color: rgb(51, 102, 255);">Other properties of Fluids :
Surface Tension
Surface energy and tension
Viscosity
Dynamic lift
Venturi meter
Torricelli's theorem
Blood flow and heart attack
Stream line flow
What is pressure ?
Pressure variation with depth
Pascal's Law
Here we consider the three interracial tensions at all the three interfaces, liquid-air, solid-air and solid-liquid denoted by Sla, Ssa & Ssl respectively as given in figure (a) and (b). At the line of contact, the surface forces between the three media must be in equilibrium. From the figure b the following relation is derived.Sla cos θ + Ssl = Ssa
The angle of contact is an obtuse angle if Ssl > Sla as in the case of water-leaf interface while it is an acute angle if Ssl < style="font-weight: bold; color: rgb(51, 102, 255);">Other properties of Fluids :
Surface Tension
Surface energy and tension
Viscosity
Dynamic lift
Venturi meter
Torricelli's theorem
Blood flow and heart attack
Stream line flow
What is pressure ?
Pressure variation with depth
Pascal's Law
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