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Electric field and potential

  1. Feb 21, 2009 #1
    Hi,

    I don't understand why dV/dr=-E

    As far as I know:
    V=kq/r
    E=Kq/(r^2)
    so V/r becomes to be E and not -E.
     
  2. jcsd
  3. Feb 21, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    What's dV/dr for that potential? Compare that to E.
     
  4. Feb 21, 2009 #3
    ohh I should derivate the function!! thank you :)
     
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