Capillary Forces Laplace Equation Liquid Curvature and Pressure Mechanical Definition

2 Capillary Forces Laplace Equation (Liquid Curvature AND Pressure) (Mechanical Definition) 

The surface tension, y, and the mechanical equilibrium at interfaces have been described in the literature in detail (Adamson and Gast, 1997 Birdi, 1989,2003a, 2009,2010a Chattoraj and Birdi, 1984). The surface has been considered as a hypothetical stretched membrane this is termed as the surface tension. In a real system undergoing an infinitesimal process, it can be written as 

FIGURE 1.12 Surface of water inside a large beaker and in a narrow tubing. The rise of water in the tubing is due to the capillary force. 

The sign of the interfadal work is designated negative by convention (Adamson and Cast, 1997 Chattoraj and Birdi, 1984). 

The fundamental property of liquid surfaces is that they tend to contract to the smallest possible area. This is not observed in the case of solids. This property is observed in the spherical form of small drops of liquid, in the tension exerted by soap films as they tend to become less extended, and in many other properties of liquid surfaces. In the absence of gravity effects, these curved surfaces are described by the Laplace equation, which relates the mechanical forces as (Adamson and Gast, 1997 Birdi, 1997 Chattoraj and Birdi, 1984) 

---