OpenStax College Physics for AP® Courses, Chapter 19, Problem 39 (Problems & Exercises)

This is College Physics Answers with Shaun Dychko. Looking at this picture in the middle we can see that the charge q one is negative and have much larger magnitude than charge q two and we know it’s a bigger magnitude of charge because these field lines that are emanating to the right from q two are curving around and going toward this charge here. So, this means a great distance away from this pair of charges. It will essentially have the same appearance as a single positive, oh sorry, negative charges cause this charge is negative charge rules because this is so much bigger than this positive one and so going with the far away, this will appear to be a point charge with some negative amount of coulombs and that means that the equipotential lines will be circles around this negative point charge and because its negative the potential is increasing as you go further away because potential is always stated in term of a hypothetical positive test charge and so a positive test charge that is really far away, has a greater potential than a positive test charge closer and the way I remember why that’s the case is because I think about how much kinetic energy could be gained by this positive test charge. Now, the positive test charge is really far away, its going to be accelerating over this huge distance all the way as being attracted to the negative charge and over that huge distance its going to gain a lot of kinetic energy and that must mean it has started with much… lots of potential energy whereas a positive test charge that starts close by has only this distance over which to accelerate and so... it will gain not very much kinetic energy, which means that this position has low potential energy.