Question

An isolated and charged spherical soap bubble has a radius 'r' and the pressure inside is atmospheric. If 'T' is the surface tension of soap solution, then charge on drop is –

• A. $2\sqrt{\frac{2rT}{\in_{0}}}$
• B. 8 p r$\sqrt{2rT \in_{0}}$
• C. 8 p r $\sqrt{rT \in_{0}}$
• D. 8 p r $\sqrt{\frac{2rT}{\in_{0}}}$

Answer 1

Answer: (B)

8 p r$\sqrt{2rT \in_{0}}$

Answer 2

Inside pressure must be $\frac { 4 \mathrm {~T} } { \mathrm { r } }$ greater than outside pressure in bubble. This excess pressure is provided by charge on bubble.

$\frac { 4 \mathrm {~T} } { \mathrm { r } }$ =

$\frac { 4 \mathrm {~T} } { \mathrm { r } }$= …

Q = 8pr