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Scalar potential in EM and Newton's Law

  1. Mar 2, 2010 #1
    Hi,all, problem is:

    in Electromagnetism, we introduced a scalar potential psi, such that:

    E = - grad Psi

    and In newton's law, there is also a scar potential U, such that:

    F= -grad U

    My question is, one is the gradient of a scalar field give a field and a force???!!

    Can anyone help me with understanding this? That would be great, and many thanks in advance!
  2. jcsd
  3. Mar 2, 2010 #2


    Staff: Mentor

    The field is just a force scaled by charge. It is the same relationship as e.g. the gravitational field and weight.
  4. Mar 2, 2010 #3
    @DaleSpam; thanks for replay. I am very interested in your answer, however, I am not quite understood it. Would you explain it more? thanks

    Can I say,

    Electric force = -grad psi = E


    Gravitation field = -grad U = F

    if they are the same.
  5. Mar 2, 2010 #4


    Staff: Mentor

    Yes. For example, if U = kCc/r then you get the electric force, if psi = kC/r then you get the electric field. Similarly, if U = GMm/r you get the gravitational force, if psi = GM/r then you get the gravitational field.
  6. Mar 2, 2010 #5
    Thanks a lot!! Cleared my mind!
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