Parallel Wires

    Two long parallel wires, each with a mass per unit length of 43 g/m, are supported in a horizontal plane by 6.0 cm long strings, as shown in Figure P19.64. Each wire carries the same current I, causing the wires to repel each other so that the angle between the supporting strings is 16°.
    Determine the magnitude of each current.

    2. Relevant equations
    sin (theta) = opposite/hyp

    I^2 = [(2pi)(d)(mg/L)] / [(4pi)e-07]

    3. The attempt at a solution

    First I found d (the distance between the wires). Which is 2[sin(8)](0.06m) = 0.0167m.
    Then I substitute the given into this equation: I^2 = [(2pi)(d)(mg/L)] / [(4pi)e-07]. I = sq.root of [(2pi)(0.0167)(0.043)(9.8)] / [(4pi)e-07]. the answer I got is 132.64 A. What did I do wrong?

    I tried using free body diagram.
    T = mg/sin8
    Tcos8 = [(I^2)(L)((4pi)e-7)] / [(2pi)d]
    (mgcos8)/(sin8) = [(I^2)(L)((4pi)e-7)] / [(2pi)d]
    (mg/L)(7.115) = [(I^2)((4pi)e-7)] / [(2pi)0.0167]
    I = 159.8 A

    Still incorrect.

    Attached Files:

    Last edited: Mar 5, 2007
  2. jcsd
  3. Ah shoot, I've made the most stupid mistake ever. I solved it.

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