Work Associated With Stretching of Liquid Film

Consider liquid film attach to a wire frame. We kno that it will take sum force to strech the film by the moveable portion of the wire frame.

(I kno this isnt a wire frame, but u get the picture)

• The force has to overcome the microscopic forces on perpendicular to any line in the surface and the forces generated by these forces per unit length is called the surface tension σ(^N/_M­).

The work associated with the stretching of a film is also called suface tension work. It is determined from   W_Surface = ∫₁²σ•dA (kJ)                (2-31)                                           
Where dA = 2b•dx is the change in the surface area of the film. The factor 2 is due to the two film surfaces that are in contact with air. The force acting on the movable wire as a result of surface tension effects is F=2b•σ_s .Where σ is the surface tension force per unit length