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Potential vs. Potential energy

  1. Oct 7, 2012 #1
    I was reading electrostatic and found out that the electric field is just the negetive divergence of potential . My questions are why are we taking the negetive divergence ? Electric field is a conservative field and so it can be written as divergence of a scaler function but why we ar taking the negetive one instead of positive . And is this potential and potential energy are same ?
     
  2. jcsd
  3. Oct 7, 2012 #2

    mfb

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    If you go down in potential energy, you lose energy. Therefore, the force should point towards points of lower potential. The direction of electric field is the force for positive charges (convention), therefore you have to take the negative derivative of the potential to get the electric field.
    The potential energy depends on the charge of the object.
     
  4. Oct 7, 2012 #3
    what do u mean by 'go down in the potential energy ' is it going nearer to the object who is responsible for the electric field ?
     
  5. Oct 8, 2012 #4

    mfb

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    If that object has a negative charge, yes, otherwise no.

    "down" -> lower potential (=lower potential energy with positive charges)
     
  6. Oct 8, 2012 #5

    sophiecentaur

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    If you 'get work out' when you move from A to B, then B is at a lower potential than A. If you have to put work in, B is a higher potential. That's the convention that's used and always applies. It avoids any confusion for situations of attraction and repulsion.
     
  7. Oct 8, 2012 #6
    So are u saying that potential and potential energy are same ?
     
  8. Oct 8, 2012 #7

    mfb

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    No, potential energy is the potential multiplied by the charge of your object.
     
  9. Oct 8, 2012 #8
    O. Thats great . Thanks
     
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