A balloon of radius 30.0 cm is sprayed with a metallic coating so that the surface is conducting. A charge of 8.85×10−8 C is placed on the surface. What is the potential on the balloon's surface?
2.65×10^3 V
Suppose that the some air is let out of the balloon, so that the radius shrinks to 13.5 cm, what is the new potential on the balloon's surface?
5.89×10^3 V
What is the change in electrical potential energy during the shrinking process? For your own interest, what does the work needed to change the potential energy?
i got the first two, need help on the third!