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Homework Help: Given Electric Potential Function Find where field is zero.

  1. Feb 17, 2009 #1
    1. The electric potential in a certain region is:
    V = ax2 +bx +c

    where a = 13V/m2
    b = -16V/m
    c = 59 V

    Determine the postion where the electric field is zero. Answer in units of m.

    2. Relevant equations

    E = -[tex]\nabla[/tex]V

    3. The attempt at a solution

    I know that the Electric Field is the negative gradient of the potential function. I then find that the partials with respect to y and z are zero. Then I find the partial with respect to x is: Ex=-13x+16
    Then find the zero to be about 1.23. But it is apparently incorrect. Any help would be appreciated.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 17, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Redo that derivative.
     
  4. Feb 17, 2009 #3
    Well the actual partial deriv. is 13x-16. Then I took the opposite to be used as the function of E.
     
  5. Feb 17, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Double check that.
    What's the derivative of that function?
     
  6. Feb 17, 2009 #5
    Thanks, I can't believe I can do some other complex integration etc and mess up a simple deriv.... mind blowing.
     
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