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Electrical force between charges

  1. Mar 27, 2014 #1
    edit: I see that my title is incorrect. This isnt between charges, it is between a charge and a point, sorry about that.

    The problem:
    Find the magnitude of the electrostatic force that works on a point 3 meters from q1.

    q1=3μC

    My attempts:
    Feq1=1/(4πε0)*(q1/r)
    r=3m
    1/(4πε0)=8.988x109

    Feq1=8.988x109*(3x10-6/3)=89.9kN

    As far as I can tell, this is the way it should be done, but the force seems pretty large... Is there something that I am missing? Or is this actually correct?
     
  2. jcsd
  3. Mar 27, 2014 #2

    SteamKing

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    Well, you can start by checking the units in your calculation, in particular Coulomb's constant. Are your formula and calculation dimensionally correct?
     
  4. Mar 27, 2014 #3
    Coulombs constant is N·m²/C², while q1/r would be C/m. So put together that would give me N*m/c... That means that there should be a C²/m², which I know to be q0*q1/r2 but that is between two charges, not the force at a point.

    I guess that means that Feq1=1/(4πε0)*(q1/r) isnt an actual equation? Which leaves me confused, because that is what was given to me in someone's notes...
     
  5. Mar 27, 2014 #4
    I spoke with the person I got the notes from, and it should have been r2 in the denominator, which would give me N/C, or the field strength. Thank you for your help.
     
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