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Homework Help: Still confused about this one

  1. Feb 8, 2004 #1
    The electric field at a distance of 10 cm from an isolated point charge of 2 x 10^-9 C is:

    A)1.8 N/C
    B)180 N/C
    C)18 N/C
    D) 1800 N/C
    E)none of these

    This is the formula I used Q=rv/k

    so (2x10^-9 C)(9x10^9 Nm^2) / .1 m C^2

    I am getting 180 N m/C - I have an extra m in the equation, which would make it none of the about. Evidently I am doing something wrong.

  2. jcsd
  3. Feb 8, 2004 #2


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    [tex] E = \frac{kq}{r^2} [/tex]
  4. Feb 8, 2004 #3
    You want E, not V.

    For a point charge:

    E = kq/r^2
  5. Feb 8, 2004 #4
    1800 N/C, thanks, nautica
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