when we placed a charge on soap bubble then the radius of charge increases why?

In an uncharged soap bubble, there is an equilibrium between positive and negative charges.When there are like charges on the surface of the bubble(negative charge in this case), the equilibrium is lost. To attain this lost equilibrium, the charges start repelling each other. These charges will end up increasing the surface area of the bubble. I hope you are able to visualize what`s happening.When the surface area increases, the bubble expands, increasing the radius.Note that, the Surface area of the bubble is directly proportional to the square root of the radius and the Volume is directly proportional to the cube root of the radius.