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How to locate Two spots where electric potential is zero

  1. Nov 11, 2009 #1
    1. The problem statement, all variables and given/known data
    A positive charge of +q1 is located 3.00m to the left of a negative charge -q2. the charges have different magnitudes.
    a) on the line through the center of the charges, the net electric field is zero at a spot 1.00m to the right of the negative charge. Determine the relative magnitude of the charges (charge ratio q1/q2)
    b) on this line there are two spots where the potential is zero. locate these two spots relative to the negative charge.

    2. Relevant equations

    3. The attempt at a solution
    for part a i got q1=+16 and q2=-1
    I'm not sure how to find these zero potential spots. I know they're supposed to be near the smaller negative value but I just can't figure out how to calculate out exactly where.
  2. jcsd
  3. Nov 12, 2009 #2

    Doc Al

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    Staff: Mentor

    q1 and q2 are magnitudes and thus positive. You found that q1/q2 = 16. Good!
    Write an expression for the total potential as a function of distance from the negative charge. You'll find it helpful to divide the line into 3 regions and write separate expressions for each region.
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