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Homework Help: Question involving resistivity using the formula?

  1. Apr 1, 2012 #1
    1. The problem statement, all variables and given/known data

    The resistivity of nichrome wire is 1.1micro ohm meters. What length of wire of diameter 0.079 mm is required to provide resistance of 1.0 Kohm?

    2. Relevant equations
    R=resistivity x length/area

    3. The attempt at a solution

    1000ohms = ? x 0.0011/0.079

    79 = ? x 0.0011

    71818.18 = resistivity

    I know I've stuffed up real bad, but this one is troubling me crazy.
  2. jcsd
  3. Apr 2, 2012 #2


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    Homework Helper

    What does "area " mean in the formula for resistance? What is the area for the 0.079 mm wire?

  4. Apr 2, 2012 #3
    Area relates to the 0.079 mm of wire. In the question it doesn't say mm squared. the answer is supposed to be 4.5 meters.
  5. Apr 2, 2012 #4


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    Homework Helper

    The diameter of the wire is 0.079 mm. The cross-section of a wire is a circle usually. The area in the formula means the area of the cross section of the wire.

  6. Apr 2, 2012 #5
    I got 4.5m for the length.
    I think you have mixed up the units.
    resistiuvity = 1.1x10^-6ohm.metre
    radius of wire = 0.0395x10^-3m
  7. Apr 2, 2012 #6
    Thanks Emily I got the answer too now. You were right I was mixing the units up.
  8. Apr 3, 2012 #7
    Hey Einstein....thanks...great help someone else
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