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Homework Help: Temperature variation of resistance

  1. Feb 8, 2009 #1
    1. The problem statement, all variables and given/known data
    A metal wire has a resistance of 8.10 at a temperature of 20°C. If the same wire has a resistance of 11.45 at 90°C, what is the resistance of the wire when its temperature is -20°C?

    2. Relevant equations

    3. The attempt at a solution
    alpha=11.45-8.1 / 11.45(70) = 4.18e-3
    R=11.45[1+(4.18e-3)(-40)] = 9.54 ohms
    But 9.54 isnt the answer...
  2. jcsd
  3. Feb 8, 2009 #2


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    Homework Helper

    Isn't the resistance at 20° = 8.1?
  4. Feb 8, 2009 #3
    Hmm.. I did that and got 6.746. It says I am within 10% of the correct value
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