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[Concept] Why is potential 0 when electric field isn't?

  1. Apr 17, 2012 #1
    Say you have a rectangle with -Q charges at top left and bottom left corners, and +Q charges at top right and bottom right corners.

    Any point along a horizontal line in the middle will have electric field going to the left, but any point along this line will have a potential of 0. I've been trying to understand this, but having trouble I get that potential is 0 because any point along this line will be equidistant from the two -Q and equidistant from the two +Q.

    I think this stems from a lack of understanding of how work and potential (and potential energy) works in an electric field.
     
  2. jcsd
  3. Apr 18, 2012 #2
    It is the gradient in potential that determines the electric field. If the potential is zero at some location but non-zero at some nearby location, there will be an electric field as a result of that potential difference. So in general you want to think about the electric field as resulting from differences in potential. This is similar to how a difference in potential generates a force in mechanics. If the potential is uniform everywhere (even if it's non-zero) there is no force.
     
  4. May 31, 2012 #3
    Would you say that it is wrong to say: a presence of charge creates an electric field... And traveling within that electric field, we will see a change in potential as long as we don't just travel perpendicular to the field lines.
     
  5. May 31, 2012 #4

    ehild

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    Don't you travel perpendicular to the field lines along the line where the potential is zero?

    ehild
     
  6. May 31, 2012 #5
    I don't think there is any reason why we would need to... or a charged particle either. We could force a particle along that line and ask some questions about it though.
     
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