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Homework Help: Point Charges

  1. Oct 23, 2005 #1
    A point charge q1 -4 nC is at the point x = 0.600 m, y = 0.800 m, and a second point charge q2 +6 nC is at the point x = 0.600 m, y = 0.
    I need to calculate the magnitude of the net electric field at the origin due to these two point charges.
    |................................. q1 (0.6, 0.8)
    Origin--------------------q2 (0.6, 0)
    To solve this problem I was thinking of taking the distances of q1 and q2 from the origin and using that as the radius, I can plug into
    E = 1/(4piEo) * q1/r^2 r = 1 q1= -4nC
    E = 1/(4piEo) * q2/r^2 r = 0.6 q2= +6nC
    and add them together to find the electric field at the origin.
    however when I did that, the answer turned out to be incorrect.
    What am I'm doing wrong? Thakn you for your help.
  2. jcsd
  3. Oct 23, 2005 #2

    James R

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    Science Advisor
    Homework Helper
    Gold Member

    Your distances are correct, but you're ignoring the fact that the electric fields from the two charges need to be added as vectors, not just numbers. You need to split the fields into components in the x and y directions, then add them.

    Does that help?
  4. Oct 23, 2005 #3
    ohh i understand now! thankyou@!!!
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