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Homework Help: Find resistance of copper wire.

  1. Sep 13, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the resistance of a 1.4 m length of copper wire with diameter of 5*10^-3 m.

    2. Relevant equations
    R = p(L/A) where p = resistivity of copper, L = length, A = area

    3. The attempt at a solution
    The resistivity of copper is (1.69 * 10^-8). Radius is d/2 (5*10^-3) / (2) = (2.5*10^-3)
    With the radius, the Area A = pi(2.5*10^-3)^2 = (1.96*10^-5).

    Plugging it into the equation R = p(L/A)
    (1.69*10^-8)*(1.4) / (1.96*10^-5) = (1.2*10^-3) Ohm

    There were two similar questions like this where the same approach yield me the correct answer. Somehow this answer I get is incorrect. What am I doing wrong?

    On a side note, how many questions may I post?
  2. jcsd
  3. Sep 15, 2010 #2
    1.2*10^-3 Ohm is the correct answer after all. It was just the faulty database in the online quiz. =D
  4. Sep 15, 2010 #3


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    Staff: Mentor

    Ouch, that hurts! Glad you got it sorted out.
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