Electric field around a large and a small conducting sphere at opposite electric potential. The shape of the field lines is computed exactly, using the method of image charges with an infinite series of charges inside the two spheres. Field lines are always orthogonal to the surface of each sphere. In reality, the field is created by a continuous charge distribution at the surface of each sphere, indicated by small plus and minus signs. The electric potential is depicted as background color with yellow at 0V together with equipotential lines.
Electric potential is the work done against an electric field in bringing a unit charge to a given point from some arbitrary reference point (usually earthed), measured in volts (i.e., joules per coulomb). Charges will tend to flow from points at one potential to those at a lower potential, and potential difference, or voltage, thus plays the role of a driving force for electric current. In inductive circuits, the work done in bringing up the charge depends on the route taken, and potential ceases to be a useful concept.