The excess pressure inside a soap bubble of radius $2 \mathrm{~cm}$ is 50 dyne $/ \mathrm{cm}^2$. The…
The excess pressure inside a soap bubble of radius $2 \mathrm{~cm}$ is 50 dyne $/ \mathrm{cm}^2$. The surface tension is
25 dyne $/ \mathrm{cm}$
60 dyne/ cm
50 dyne $/ \mathrm{cm}$
75 dyne/ cm
Solution
Given,
Excess pressure, $\Delta P=50$ dyne $/ \mathrm{cm}^2$
Radius, $r=2 \mathrm{~cm}$
For a soap bubble liquid-air interface is crossed two times, so we have,
Excess pressure, $\Delta P=\frac{4 T}{r}$, where $\mathrm{T}$ is the surface tension.
$\therefore T=\frac{\Delta P \times r}{4}=\frac{50 \mathrm{dyne} / \mathrm{cm}^2 \times 2 \mathrm{~cm}}{4}=25 \mathrm{dyne} / \mathrm{cm}$