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## Homework Statement

Find the amount of charge required to double the radius of a bubble of radius r and surface tension T.

## Homework Equations

Increase in surface energy of bubble = T ΔA

## The Attempt at a Solution

I've tried equating the increase in surface energy to the work done by the Coulomb force, but I'm finding a lack of information. Do I just assume that the charge is some distance away from the bubble? Then what will be the integration limits for F . dr?