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Find Tension in String Connecting Two Charged Spheres

  1. Jun 12, 2013 #1
    Two charged objects of charge q.

    Coulomb's law states that the force on one sphere by the field of the other is:

    F = qE

    But each sphere experiences that, correct? So the tension for the string would be 2F. Is that correct?
  2. jcsd
  3. Jun 12, 2013 #2

    rude man

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    Take one of the spheres and write sum of forces on it = 0 (since the sphere is not accelerating).
  4. Jun 12, 2013 #3


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    Welcome to PF.

    Let's think about this. Each charged sphere has two forces exerted on it. Some questions to help you think about the situation:

    1. What are the two forces acting on one of the spheres? (Take the sphere on the left, for example). Obviously one of the forces is the electric force as given by Coulomb's law, so this question is really asking you to identify another force that acts on a sphere.

    2. What is the acceleration of that sphere -- and therefore ...

    3. What is the net force acting on that sphere?
  5. Jun 12, 2013 #4
    Well there's the force of the first particle1 onto the particle2 and then there's the equal and opposite reaction from particle 2's force onto particle 1.
  6. Jun 12, 2013 #5


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    No, you're still trying to look at it from both perspectives at once. Concentrate on the forces to which one sphere is subjected. That's both electrostatic force and tension.
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