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Why the electric field around a positive charge is always directed away from it?

  1. Aug 3, 2015 #1
    Hello everyone!
    My question is: why the electric field around a positive charge is always directed away from it? and why not towards?
     
  2. jcsd
  3. Aug 3, 2015 #2
    Gauss Law says the electric field is directed away from a positive charge. ##\nabla E=\rho##
    The sign is convention. Gauss Law could have been, ##\nabla E=-\rho##, and with changes of sign made to ##\rho## and ##J## in the rest of Maxwell's equations and the Lorentz equation of electromagnetic force, it would be just as useful.
     
    Last edited: Aug 3, 2015
  4. Aug 3, 2015 #3
    Because it is repulsion.

    The gravitational field is measured by keeping a unit positive charge in the field. The positive-positive repulsion makes the force away from it.
     
  5. Aug 3, 2015 #4

    CWatters

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    A repulsive gravitational field could be very useful :-)
     
  6. Aug 3, 2015 #5

    Drakkith

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    That's not correct. The direction of the field is completely arbitrary. We denote it as being directed away from positive charges simply because of convention.
     
  7. Aug 3, 2015 #6
    Yes, because of convention. I mentioned that in this statement

    Maybe I should have added that the measurement is done in the direction the unit positive charge (point charge in fact) moves. I meant by "Measurement done"=how we measure it (conventionally)
     
  8. Aug 5, 2015 #7
    Convention . You could consider - we draw electric field lines moving away from +ve charges , and moving towards -ve charges - as given by Faraday .

    This is simply convention .
     
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