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Finding Electric Field at point P

  1. Jan 29, 2012 #1
    1. The problem statement, all variables and given/known data
    Two charges are located in the (x, y) plane as
    shown. The fields produced by these charges
    are observed at a point p with coordinates
    (0, 0). Find the x-component of the electric field
    at p. The value of the Coulomb constant is
    8.98755 × 109 N · m[itex]^{2}[/itex]/C[itex]^{2}[/itex].
    Answer in units of N/C


    2. Relevant equations
    k[itex]_{c}[/itex] = 8.98755E9
    cos θ[itex]_{12}[/itex] = [itex]\frac{1.7}{sqrt(8.65)}[/itex]
    cos θ[itex]_{13}[/itex] = [itex]\frac{1.6}{sqrt(8.32)}[/itex]
    q[itex]_{2}[/itex] = -8.1 C
    q[itex]_{3}[/itex] = 7.9 C
    r[itex]_{12}[/itex] = [itex]sqrt(8.65)[/itex]
    r[itex]_{13}[/itex] = [itex]sqrt(8.32)[/itex]

    3. The attempt at a solution
    E[itex]_{x}[/itex] = -(k[itex]_{c}[/itex]|q[itex]_{2}[/itex]|cos θ[itex]_{12})/r_{12}^{2}[/itex] - (k[itex]_{c}[/itex]|q[itex]_{3}[/itex]|cos θ[itex]_{13}[/itex])/r[itex]_{13}[/itex][itex]^{2}[/itex]

    = -k[itex]_{c}[/itex]([itex]\frac{8.1}{8.65}[/itex] * [itex]\frac{1.7}{sqrt(8.65)}[/itex] + [itex]\frac{7.9}{8.32}[/itex] * [itex]\frac{1.6}{sqrt(8.32)}[/itex])

    is this the right way to do it?
     

    Attached Files:

    Last edited: Jan 29, 2012
  2. jcsd
  3. Jan 29, 2012 #2

    rude man

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    Hard to say since you didn't show or describe the locations of the charges ...
     
  4. Jan 29, 2012 #3
    sorry here is the picture
     
  5. Jan 29, 2012 #4

    SammyS

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    attachment.php?attachmentid=43259&d=1327869883.png

    Not quite alright.

    Where are the angles, θ12 , θ13 ?
     
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