Occasionally I need to undrstand electric fields and I usually find an equation that allows me to solve my problem without understanding the solution. Dangerous but.... Anyway I've encountered another field problem and now I'd like to understand the solution to the problem. Put in general terms I'd like to understand what the charge in Coulombs might be on the positive post of a 12 V battery that is fully charged but in which there is no external connection (other than air) between the positive and negative posts. Further, if the post can be treated as a point source is it reasonable to use Coulombs Law to calculate the electric field at a given distance (say 10 cm) directly above the post. Intuitively it seems the post should bear a coulombic charge and thus act as a point source but I'm having trouble proving to myself that my intuition is in agreement with fact.