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Homework Help: Resistance of copper wires

  1. Apr 4, 2010 #1
    1. The problem statement, all variables and given/known data

    a copper wire of length of length L and cross sectional area A has resistance R. A second copper wire at the same temperature has a length of 2L and a cross sectional area of 1/2 A. what is the resistance of the second copper wire?

    2. Relevant equations

    R = pL/A

    L = 2
    A = 1/2
    p = how do i find p

    3. The attempt at a solution

    p stand for resistivty but how do i know it in this problem
     
  2. jcsd
  3. Apr 4, 2010 #2

    rl.bhat

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    Re: resistance

    In the relevant equation replace L by 2L and A by A/2 to get new resistance.
     
  4. Apr 4, 2010 #3
    Re: resistance

    oh should the answer come out to be 1R
     
  5. Apr 4, 2010 #4

    ideasrule

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    Re: resistance

    yes.
     
  6. Apr 4, 2010 #5

    rl.bhat

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    Re: resistance

    No.
    New resistance R' = ρ*2L/A/2 = .......?
     
  7. Apr 5, 2010 #6
    Re: resistance

    i think p would be 1.72 x 10 exponent -8 since it is on copper
    so i do 1.72x10 exponent -8 * 2 m/ 2 a is that the right equation?
     
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