the questioon is this: A balloon of radius 34.5 cm is sprayed with a metallic coating so that the surface is conducting. A charge of 1.05 × 10-08 C is placed on the surface. What is the potential on the balloon's surface? how i solved it: -apply the guass law, which gives me the Electrical Field. -apply the formula : Voltage = Ed , where E = electrical field , & d = distance travelled by charges (parrallel to field line) n it turn out d = 34.5cm. this is where i don't get. why its d = 34.5cm? its it b/c the positive charge move to the center, which travel a distance of 34.5cm? since if the surface is positively charged, it would repel the " + " charge to the centre & attact the " - " charge to surface....right?