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Homework Help: Point charges in an electromagnetic field

  1. Sep 3, 2011 #1
    point charges in an electric field

    1. The problem statement, all variables and given/known data
    Problem: A +8.75 micro C point charge is glued to a frictionless table. It is tied to -6.5 micro C point charge by a 2.5 cm string (weightless and nonconducting). A uniform electric field of magnitude 1.85*10^8 N/C is directed parallel to the wire toward the positive charge. a) what is the tension in the wire? b) what would the tension be if both charges were negative?

    2. Relevant equations

    E(vector)= F(vector)/(q)

    3. The attempt at a solution

    using coloumbs law I attempted to find the force between the 2 particles. but from there i am pretty lost can anyone help?
    Last edited: Sep 3, 2011
  2. jcsd
  3. Sep 3, 2011 #2

    q1= 8.75*10^-6 C
    q2=-6.5*10^-6 C
    r=.025 m

    so Force=(8.988*10^9) X (q1*q2)/r^2 = 8.1*10^-4 N (q1*q2) is absolute value

    but where do i go from here?
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