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Homework Help: Resistance of a piece of metal

  1. Mar 7, 2010 #1
    1. The problem statement, all variables and given/known data

    How does the resistance of a piece of metal change if both its length and its diameter are reduced to one half their original values?
    Question 1 answers
    It is increased to 4 times the original value
    It doubles
    It remains unchanged
    It is halved
    It is reduced to 1/4 of the original value

    2. Relevant equations

    R = pL/A where P is the resistivity constant

    3. The attempt at a solution

    I am not sure how to relate the area to change in area
  2. jcsd
  3. Mar 7, 2010 #2
    Re: Resistance

    I think you can assume it's a round wire.
  4. Mar 7, 2010 #3


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    Homework Helper

    Re: Resistance

    they call one dimension a "diameter" , which becomes half
    ... how does the new Area compare to the old Area ?
    (it's not about _change_ , it is about new = "some number" times old)
  5. Mar 7, 2010 #4
    Re: Resistance

    Assume it's a round wire, with diameter d, the new diameter will be d/2.
    old length is L, new length is 2L

    Calculate old and new resistance, compare.
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