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Homework Help: Equipotential lines and electric field lines

  1. Mar 1, 2012 #1

    ktb

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    1. The problem statement, all variables and given/known data
    I am given the equation for the potential of an arbitrary dipole. I need to draw the electric field lines for this dipole in a plane, and also show that these lines are perpendicular to the equipotential lines. I have already derived the equation for the electric field using the gradient of the potential and mapped out the equipotential lines.
    


    2. Relevant equations
    V d i p ( ⃗r ) = Constant ⃗r ·p⃗ /(r^3)
    E⃗ d i p = − ∇⃗ V d i p
    = (Constant) 3( ⃗r · p⃗) ⃗r /(r^5) - p⃗/(r^3)
    Take p⃗ to equal a unit vector for an orthonormal basis. Such as the unit vector for x in the x, y, z coordinate system.


    3. The attempt at a solution
    I know that the gradient of V is always perpendicular to V, so intuitively this makes complete sense. However, I do not know how to show that a scaler quantity (V) is perpendicular to the vector equation I derived for E. I am also unsure how to map such a strange function for E into ℝ2 although obviously I know what it looks like.
     
  2. jcsd
  3. Mar 2, 2012 #2

    ktb

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    Figured it out. Bad misunderstanding on my part about El. field lines.
     
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