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Resistance and ohm's law

  1. Dec 5, 2007 #1
    1. The problem statement, all variables and given/known data

    the tungsten filament of a light bulb has a resistance of .07 ohm. if the filament is 27 cm long, what is the diameter



    2. Relevant equations

    R= p(L/A)

    Area of a circular cross section = (PiD^2/4)

    3. The attempt at a solution

    R= p(L/A) A= (pL)/r

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

    resistance .07 ohm. lengh= .27m, resistivity= 5.6x10^-8
    diameter ?

    2. Relevant equations

    A= (pL)/r
     
  2. jcsd
  3. Dec 5, 2007 #2
    can i get some help
     
  4. Dec 5, 2007 #3

    marcusl

    User Avatar
    Science Advisor
    Gold Member

    Ok, you have the right equations. From the last equation you wrote and the values you listed, what is the area A?

    Once you have that, find the diameter from d=2*sqrt(A/pi).
     
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