# Surface Tension: Pressure Diff & Cross-Sectional Area Explained

• KishoreAM
In summary, when calculating the relationship between Pressure Difference and Surface Tension in a droplet, we use the cross sectional area because the pressure acts perpendicular to the surface. This also applies to bubbles.
KishoreAM
Hi Guys...
I have a small doubt regarding surface tension.
When calculating the relation between Pressure Difference inside and outside a Droplet and Surface Tension, we multiply Pressure Difference with Cross Sectional Area of the Droplet and equate it to the Surface tension force.
My doubt is "Why do we use Cross Sectional Area, but not Total Surface Area of the Droplet?" (Pressure acts over the whole surface)

KishoreAM said:
Hi Guys...
I have a small doubt regarding surface tension.
When calculating the relation between Pressure Difference inside and outside a Droplet and Surface Tension, we multiply Pressure Difference with Cross Sectional Area of the Droplet and equate it to the Surface tension force.
My doubt is "Why do we use Cross Sectional Area, but not Total Surface Area of the Droplet?" (Pressure acts over the whole surface)
The pressure acts perpendicular to the surface of the drop. If you determine its component normal to the cross section of interest and integrate that over the surface of the drop, the result is just the pressure times the cross sectional area.

## What is surface tension?

Surface tension is a measurable physical property that describes the force required to break or stretch the surface of a liquid. It is caused by the cohesive forces between the molecules of the liquid, and is typically measured in units of force per unit length.

## How does surface tension affect pressure?

Surface tension can have an impact on pressure in a liquid when there is a change in the cross-sectional area of the container holding the liquid. This is known as the Laplace equation, and it states that the pressure within a liquid is directly proportional to its surface tension and the curvature of its surface.

## What is the relationship between surface tension and pressure differential?

The relationship between surface tension and pressure differential is that surface tension can create a pressure differential between two points in a liquid. This can occur when there is a change in cross-sectional area or when there are two different types of liquids with different surface tensions in contact with each other.

## How does cross-sectional area affect surface tension?

The surface tension of a liquid is inversely proportional to its cross-sectional area. This means that as the cross-sectional area increases, the surface tension decreases. This is due to the fact that a larger area means there are more molecules on the surface, which reduces the cohesive forces and therefore the surface tension.

## How can surface tension be measured?

Surface tension can be measured using various methods, such as the drop weight method, the capillary rise method, or the Du Noüy ring method. These methods involve measuring the force required to break or stretch the surface of a liquid and using mathematical equations to calculate the surface tension.

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