Where on this plot is the electric field zero? Where is the potential zero?
Imagine two point charges, as in the picture above, each having a magnitude Q. If they were brought together until they were touching, how would the equipotential lines change?
If you were to take two equal point charges (as in the plot at the top of this page) and separately plotted Ex versus x, and Ey versus x, at a fixed value of y=.01 and Q=.1, what would you expect to see?
If you understand all these questions, go on to learn about two opposite point charges.