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Homework Help: Electric Field- Infinitely long lines of charge

  1. Apr 5, 2012 #1
    Two very long uniform lines of charge are parallel and seperated by 0.3m. Each line of charge has charge per unit length: +5.20*10^-6. What is the magnitude of the force that one charge exerts on a 0.0500m section of the other line of charge?

    My Attempt

    Standard formula for the E field of an infinite line charge is :λ /2πΣσr

    E = 5.20*10^-6/2π*8.85*10-12*0.3
    Q(of this section)= 5.20*10^-6*0.05

    => F = EQ = 0.0810 N

    However the correct answer is , 4.05*10^-3 N

    Cheers Guys =]
  2. jcsd
  3. Apr 5, 2012 #2

    current induces magnetic field
    B = uI/(2*pi*r)
    the force experienced by a moving charge is IxB
    F = IxB
    that current crossed with magnetic field
    so the current from 1 is crossed with the current from 2
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