Excess Pressure MCQ - Practice Questions with Answers

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 the Drop or bubble increases. This internal pressure increases until the equilibrium is achieved. So that is why in equilibrium the pressure inside a bubble or drop is greater than outside. 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

$$
\Delta P=0
$$

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

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

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

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

4. Pressure Difference in Water Droplet

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

5. Change in Pressure of bubble in the air

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

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