Question

The size of the soap bubble increases due to mechanical force exerted on the surface by electrification.Justify the statement

Answer 1

When you provide some charge to a soap bubble, due to the repelling force between the charges, they will try to be as far as possible to minimize the overall potential energy. Also, this is facilitated by the hydrophilic end of the soap molecules. Hydrophilic ends are usually in contact with the air, on the outside and inside surfaces of the soap bubble and the ionic nature of these will help in uniform spreading of the charges.

Now, we have a soap bubble whose surface is uniformly charged, this uniform distribution minimizes the potential energy and no other distribution without changing the size of the bubble has lower energy.
The bubble can increase in size and since increase in the surface area of the bubble further reduces the charge density, this will further reduce the electrostatic potential. But, the issue is by increasing in size, there will be a pressure difference between the inside and the outside of the bubble. This pressure difference will try to squeeze the bubble smaller.