We have a good idea of what electric field is. We've drawn a lot of pictures; we've made a mathematical model and applied it to some situations. But we don't have a good picture of electric potential energy. So we started by drawing an analogy to gravitational potential energy. We defined gravitational potential as the amount of gravitational potential energy per kilogram. We got out the contour maps and saw how these contour lines are isolines—lines of equal gravitational potential. We talked about it as a class and then in groups. We're starting to see a connection between these equipotential lines and electric field lines.