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Homework Help: At what points is the potential zero?

  1. Oct 20, 2005 #1
    I was wondering if someone could help get me started on this problem. I thought I knew how to solve it but keep coming up with the wrong answer:

    A 2.9 µC is at x = 0 and a -2.0 µC charge is at x = 3.5 cm. (Let V = 0 at r = .)

    (a) At what point along the line joining them is the electric field zero?
    x = cm
    (b) At what points is the potential zero?
    x = cm (smaller x value)
    x = cm (larger x value)

    a) [(2.9e-6 C)k]/(.055+ x)^2 = [k(2e-6)]/(x^2)

    k's cancel.. and then use quadratic to find it but the values aren't the right ones... What am I missing???

    Any help would be appreciated!!!
  2. jcsd
  3. Oct 20, 2005 #2

    Tom Mattson

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    Staff Emeritus
    Science Advisor
    Gold Member

    Your problem is that you've got the [itex]2.9\mu C[/itex] charge sitting at x=-0.55cm, and you've got the [itex]-2\mu C[/itex] charge sitting at the origin.

    (edited for typos)
  4. Oct 20, 2005 #3
    well yeah I guess that would make things a little more difficult! haha thanks!!!
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