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Homework Help: Find the Electric Field strength

  1. Apr 3, 2010 #1
    1. The problem statement, all variables and given/known data
    "A copper cable carrying 50A current has radius 0.003m. What is the electric field if copper has a resistivity of 1.7x10^-8 Ohm/m?"

    2. Relevant equations
    Formula for current density etc.

    3. The attempt at a solution

    So I write:
    [tex]\vec{\mathbf{J}} = n|q|v_d = \frac{I}{A}[/tex]

    And then:
    [tex]\vec{\mathbf{J}} \cdot \rho = \frac{I}{A} \cdot \frac{RA}{L} = \frac{V}{L}[/tex]

    And now do I just apply the work energy theorem?:
    [tex] \int \vec{\mathbf{E}} \cdot d\vec{\mathbf{l}} = \Delta V_{ab}[/tex]

    It kind of feels as though I'm completely off tbh...
  2. jcsd
  3. Apr 3, 2010 #2


    User Avatar
    Homework Helper

    Use Ohm's law [itex]\mathbf{J}=\sigma \mathbf{E}[/itex].
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