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Homework Help: Calculate the y component of the electric field at a generic point(x,y)

  1. Sep 3, 2011 #1
    1. The problem statement, all variables and given/known data

    an electric dipole is placed in the x-y plane, with the positive charge +q placed in position (+a, 0) and the negative charge -q placed in position (-a, 0)

    define r(subscript +) and r(subscript -) the vectors connecting the point defined by r and the two points (+a, 0) and (-a, 0), and r(subscript+) and r(subscript -) their magnitudes; calculate the y component of the electric field at a generic point (x, y) of the plane as a function of r(subscript +) and r(subscript -) (it is quicker to use directly the field equation from a point charge than using the potential)

    3. The attempt at a solution

    E=-gradV=q/(4 pi epsilon0)(1/(r^2)) r-hat

    E=q/(4pi epsilon0) [(1/([r(+)]^2 +(x+a)^2))+(1/([r(-)]^2 + (x-a)^2))]
     
  2. jcsd
  3. Sep 3, 2011 #2
    In the above was a hint:

    "... (it is quicker to use directly the field equation from a point charge than using the potential) ... "

    The first line of your solution you have E=-gradV ...

    I think you are to just add two electric vectors?
     
  4. Sep 4, 2011 #3
    sorry, I still don't understand. where have I gone wrong?
     
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