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Resistance versus Temperature

  1. Sep 8, 2009 #1
    1. The problem statement, all variables and given/known data

    A copper wire has a resistance of 0.501 ohms at 20.0 degrees C, and an iron wire has a resistance of 0.466 ohms at the same temperature. At what temperature are their resistances equal?



    2. Relevant equations

    R = Ro {1 - coefficient of expansion *(T - To)}


    3. The attempt at a solution

    R(iron) = Ro {1 - coefficient of expansion *(T - To)}

    R(copper) = Ro {1 - coefficient of expansion *(T - To)}

    I set R(iron) = R (copper) and solved for the Temperature final, but the answer was wrong. Can you help me? Thanks!
     
  2. jcsd
  3. Sep 8, 2009 #2

    Mapes

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    The increase in resistance due to a length increase via thermal expansion is probably negligible compared to the increase in resistance due to a positive temperature coefficient of resistivity.
     
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