Physics 201- Introduction to Electricity & Magnetism
September 9- Calculating Electric Fields






  Here's the recipe for quantitatively determining the electric field due to a collection of point charges:
  • Sketch the electric field, not only at the location(s) you are interested in, but also at all locations (this will help you get a better intuitive sense of what is going on).
  • Look at each point charge separately, finding the field due to each.  At the end we will combine the fields to find the total field.
  • Find the magnitude of the electric field of your first charge at the location(s) of interest.
  • Draw this vector, so you can break it into components (x-y is usually the easiest)
  • Repeat these steps for each point charge.
  • Sum the x components, and the y separately.  This gives you the total electric field at your location(s).


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Jeff Phillips
Loyola Marymount University
Fall 2002