Calculate Electric field from two point charges

  1. [SOLVED] Calculate Electric field from two point charges

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

    Two point charges with q1=2x10^-5 and q2=-4x1-^-3 are located in free space at (1,3,-1) and (-3,1,-2), respectively, in a cartesian coordinate system. Calculate the electric field E at (3,1,-2)

    2. Relevant equations

    E=(1/4piE0)(-qr1/r1^3+qr2/r2^3)

    3. The attempt at a solution

    I understand the above equation but am unsure of how to implement it using cartesian coords?
     
    Last edited: Feb 12, 2008
  2. jcsd
  3. Kurdt

    Kurdt 4,941
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    The distance between two points is:

    [tex] s = \sqrt{(x_1-x_2)^2+(y_1-y_2)^2+(z_1-z_2)^2} [/tex]
     
  4. how do i use the vector in this part of the equation though?

    q1r1/r1^3

    the r1 on top is still a vector...

    and then i presume for the bottom part i just take the magnitude of r1 and cube it?
     
  5. Kurdt

    Kurdt 4,941
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    Well I've given you the magnitude of the vector so what do you imagine its components to be?
     
  6. just (x,y,z) surely?
     
  7. Kurdt

    Kurdt 4,941
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    Make that: [itex] ((x_1-x_2) \mathbf{\hat{i}}+.....) [/itex] etc.
     
  8. Awesome, thanks!
     
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