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Electric charge attraction and repulsion

  1. Feb 29, 2008 #1
    The basic law of electric charge fields is that like charges repel and unlike charges attract. This does not come out of the equations but is inserted as just an empirical observation that must be allowed for, is it not ? Am I missing something here? Compare gravity that is always an attractive force. Will this fall out of the superstring theory of everything?
  2. jcsd
  3. Mar 1, 2008 #2
    String theory has NOTHING to do with this. Essentially, classical physics describes these phenomena, it does not explain why the gravitational force is attractive ! That's an important nuance that needs to be made here.

  4. Mar 2, 2008 #3


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    In the simplest terms, the sign of the potential energy determines the direction of the force. In the electric case, this is proportional to the product of two charges, which may be positive or negative in sign. Like charges give positive potential energy ( repulsive force) and unlike charges give negative potential energy (attractive force).

    We only know one 'charge' for mass, so that makes it different.

    It is not actually as arbitrary as you suggest when you say -

    And forget string theory, it is is not the answer.
  5. Mar 2, 2008 #4
    Like charge repel and unlike charges attract. The force with which the attraction or repulsion takes place is the same and is given by the Coulomb's law. The forces directions come from the likeness or unlikeness of the charges. The magnitude/directionof the forces every thing is based on the empirical observation and is described using an equation.
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