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Find the resistance of a wire after it is stretched

  1. Feb 25, 2010 #1
    1. The problem statement, all variables and given/known data
    A wire is lengthened to 1.25 times its original length by pulling it through a small hole. Find the resistance of the wire after it is stretched.



    2. Relevant equations

    resistance=(resistivity)(length)/(area)



    3. The attempt at a solution

    Umm..the reasoning behind this is that the initial area times length should equal the final area times length. However, I am not sure why this "conservation of volume" applies. Is it because the current is constant so the volume must remain constant?

    What does it mean pulling it through a small hole?
     
  2. jcsd
  3. Feb 25, 2010 #2

    mgb_phys

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    Science Advisor
    Homework Helper

    Re: Wires

    Volume is conserved because you aren't changing the amount of metal or the density.

    So yes the area is reduced by a factor of 1.25, less area means more resistance.
     
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