Excess Pressure - Practice Questions & MCQ

Excess Pressure- 

Definition-Difference of pressure between the two sides of the liquid surface is known as Excess Pressure.

Cause of Excess Pressure-

Drop or bubble tends to contract and so compresses the matter enclosed, due to the property of surface tension. Thus to prevent further contraction, internal pressure inside Drop or bubble increases. This internal pressure increase until the equilibrium is achieved. So that is why in equilibrium the pressure inside a bubble or drop is greater than outside. And this difference of pressure between the two sides of the liquid surface is called excess pressure.

• Excess pressure in different cases 

1. Excess pressure for plane surface

   $\mathrm{\Delta }P=0$

   means No difference in pressure.
   2. Excess pressure for concave surface

   $\mathrm{\Delta }P=\frac{2T}{R}$

   
   Where
   T- Surface Tension
   R- Radius
   3. Excess pressure for a convex surface

   $\mathrm{\Delta }P=\frac{2T}{R}$

   4. Pressure Difference in Water Droplet

   $\mathrm{\Delta }P=\frac{2T}{R}$

   5. Change in Pressure of bubble in the air

   $\mathrm{\Delta }P=\left(\frac{2T}{R}\right)\times 2=\frac{4T}{R}$
    

•         Excess pressure is inversely proportional to the radius of the bubble (or drop).