1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electric Field between 2 Point Charges

  1. Jan 27, 2008 #1
    [SOLVED] Electric Field between 2 Point Charges

    1. The problem statement, all variables and given/known data

    Two point charges are placed on the x axis. The first charge, q1 = 8.00 nC, is placed a distance 16.0 m from the origin along the positive x axis; the second charge, q2 = 6.00 nC, is placed a distance 9.00 m from the origin along the negative x axis.

    Find the electric field at the origin, point O.

    Give the x and y components of the electric field as an ordered pair. Express your answer in newtons per coulomb to three significant figures. Keep in mind that an x component that points to the right is positive and a y component that points upward is positive.

    2. Relevant equations
    E = F/q
    F = kq1q2/r^2
    E = p / (2pi * e0 * x^3)
    p = qr

    q1 = 8*10^-9
    q2 = 6*10^-9
    r = 9+16 = 25 (The distance between the two point charges)
    e0 = 8.85*10^-12
    x = r (Assumably, not for certain)

    3. The attempt at a solution
    Since both charges are along the x axis, I conclude that they do not pose any influence on the y coordinate of the field, therefore the y coordinate is 0.

    The x coordinate can be computed via E = F/q.
    We are trying to calculate E.
    F can be calculated via F = kq1q2/r^2
    Issue is, what do we use for q?

    Alternatively, we could use p = qr to find p (But again, which q to use?)
    Then we can use E = p / (2pi * e0 * x^3)
    (But then which x do we use? 9, 16, or 25? Distance between a point and (0,0), or distance between both points?)
  2. jcsd
  3. Jan 27, 2008 #2
    I think you're making this too hard. All you need to do is find the electric field at the origin due to [tex]q_1[/tex] and add it to the electric field at the origin due to [tex]q_2[/tex]. In other words,

    [tex]\vec{E} = \vec{E}_1 + \vec{E}_2[/tex]
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?