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Electric field and equipotential lines

  1. Mar 3, 2006 #1
    just a coupla quick questions:

    1) in a parallel plate capacitor, we have field lines and equipotential lines. field lines show direction from the + to the - plate, but equipotential lines have no direction. why is this?

    2) what happens to the electric field near the edges of the plates?

    3) if you have a positively charged plate and place a negatively charged point charge above it, what does the electric field look like on them?

    for part 1, i know that field lines have direction because it is an electric force acting in a certain direction, but im not too sure about this equipotential stuff. i figure that the equipotential lines have no direction because they have no force acting on them at those points, i'm not too sure though....

    for part 2, i know that between the plates the field is uniform and the strongest, so at the edge of the plates it becomes less intense and non-uniform?

    for part 3, i know field lines go from + to - charges, but this is a plate and all the E lines radiate out from it, im not sure if they all just go into the negative charge or what the deal is really
    i dunno, any help would be appreciated
    Last edited: Mar 3, 2006
  2. jcsd
  3. Mar 3, 2006 #2
    1. Equipotentials simply connect all the points that have the same potential energy (if a particle was there), and so you can move along them and do no work, and as such have no associated direction (unlike field lines).

    2. Towards the edges of the plates, the eletric field becomes a little distorted, and so technically isn't a uniform field, so yes you are right.

    3. I think that the E lines do because the positive and the negative attract.
  4. Mar 3, 2006 #3
    One or two comments to add to finchie_88's post.

    Equipotential lines mark the value of the electric potential, which is a scalar quantity, so we would expect no direction to be associated with it. Electric fields are vectors, so we would want to know a direction.

    Depends on what you mean by "edges." Macroscopically, which is what I assume you are talking about (as opposed to quantum), when an electric field line meets a conductor the electric field is perpendicular to the conductor. If you are talking about a corner, all H*ll breaks loose. Field lines tend to congregate around points so the corners can be rather packed with field lines. The sharper the point, the more intense in general. (There is, of course, a limit to that depending on the overall energy of the field.) This is essentially how a lightning rod works...they come to a point, so the lightning, which is a flow of charged particles, tends to be attracted more to that point.

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