Question

There is a soap bubble in air, having radius $R$ and surface tension $T$. The pressure difference across the two surfaces of the soap bubble, given the atmosphere is $P_0$ is

• A. $P_0+\frac{2T}{R}$
• B. $\frac{4T}{R}$
• C. $P_0+\frac{4T}{R}$
• D. $P_0-\frac{4T}{R}$

Answer 1

Answer: (B)

$\frac{4T}{R}$

Force due to surface tension $=TL$

$=T\left(4\pi R\right)$

Pressure generated due to surface tension.

$P=\frac{F}{Are}=\frac{T\left(4\pi R\right)}{{\pi R}^2}=\frac{4T}{R}$