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Electric fields- the force exerted on a given charge

  1. Nov 24, 2009 #1
    why is there a different equation for force in a uniformed electric field F=E/Q as opposed to the electric field between a pair of oppositely charged plates F=EQ ?

    I thought it would be the same as the field between a pair of oppositely charged plates are also relatively uniformed, in the centre that is.

    also how is the equation F=E/Q when E=F/Q ?:confused:
  2. jcsd
  3. Nov 24, 2009 #2


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    F=qE, in the absence of a magnetic field, as given by the Lorentz force equation.
  4. Nov 25, 2009 #3
    F = qE is a general relation. In a parallel plate capacitor E is relatively uniform due to the geometry of charge distribution, so F is uniform.

    In a more general situation one must examine how the E field varies in space due to charge distribution in the local region, there E varies in space and F varies too. See Coulomb's Law or a reference on electrostatic fields.
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