Types of Molecular forces
- Force of cohesion: The force of attraction between the molecules of the same substance is called force of cohesion or cohesive force.
- Force of adhesion: The force of attraction between the molecules of the different substances is called the force of adhesion or adhesive force.
Surface Tension
Surface Tension is the property of liquid at rest by virtue of which its surface behaves like a stretched membrane and tries to occupy minimum possible surface area is called surface tension.
Mathematically, it is the force per unit length of an imaginary line drawn in the plane of the liquid surface acting right angles to this line. If F is the force acting on the imaginary line of length l, then
Relation between surface Tension and Surface Energy
Consider a rectangular frame of wire ABCD as shown in the figure in which wire BC is movable. If we dip the frame in a soap solution, a thin film is formed which pulls the wire BC toward left due to surface tension. It T is surface tension of the film and l is length of wire BC, then the force F on BC due to surface tension is given by,
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