How to graph equipotential lines of two charges?

  1. The two charges are (-q) and q. I'm just curious as to how you go about graphing them.

  2. jcsd
  3. You have a dipole, which field you want to graph.
  4. When you say field are you talking about the electric field lines? I know that when you draw the electric field lines that the equipotential lines are perpendicular to them. I'm lost as how to draw the electric field lines. I've been looking through my book and online, but can't find a way to draw them given that you have a dipole.
  5. jtbell

    Staff: Mentor

    To get an approximate graph by hand:

    1. Calculate the total electric field (from both charges, as a vector sum, with magnitude and direction) at many points, e.g. on a grid that covers the region around the charges.

    2. At each point, draw an arrow that points in the direction of the field at that point.

    3. By inspection ("eyeballing") you should be able to draw a set of lines that run from one charge to another (if the total charge is zero) or from one charge to infinity (if the total charge is not zero), and curve in such a way as to run more or less parallel to nearby arrows. These are field lines.

    4. Draw a set of lines that always intersect the field lines perpendicularly. These are equipotential lines.

    This should work, in principle, for any number of charges of any strength.
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