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Derivation of the electric field from the potential

  1. Sep 26, 2004 #1
    I am studying for a test and i can't figure out for the life of me how my book derived the solution for this problem I know it has to be basic i just dont see it...

    An electric dipole consists of two charges of equal magnitude and opposite sign separated by a distance 2a... The dipole is along the x axis and is centered at the origin.
    calculate V and Ex if point P is located anywhere between the two charges.

    I understand the concept of this, and have calculated V, which is [ (2*(Ke)*q*x) / ((a^2) - (x^2)) ] and i know how to start the problem of Ex...

    Ex = - (dV/dx) = - [ (2*(Ke)*q*x) / ( (a^2) - (x^2) ) ....

    But I can't remember or figure out for the life of me how they got

    = - 2*(Ke)*q * [ { (a^2) + (x^2) } / { ( (a^2)-(x^2) )^2 } ]

    Can Anyone please help? :D
  2. jcsd
  3. Sep 26, 2004 #2
    try using the quotient rule for the derivation!!!! You will get it!!!
  4. Sep 26, 2004 #3

    Doc Al

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    Staff: Mentor

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