I'm learning about charge right now and I have no idea how to start this one.. any help is appreciated. A helium balloon has a charge of q = 5.5 x 10^-8. It rises vertically into the air. d = 600m. from the surface of the earth to final position A. The electric field that normally exists in the atmosphere near the surface of the earth has a magnitude E = 150 N/C and is directed downward. What is the difference in electric potential between the two positions?