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Homework Help: Homework help- electrical resistance

  1. Feb 22, 2010 #1
    1. The problem statement, all variables and given/known data

    A 2.5 cm length of tungsten filament in a
    small lightbulb has a resistance of 0.041
    .
    Find its diameter. (The resistivity is
    5.6 × 10−8
    · m).
    Answer in units of mm.

    2. Relevant equations

    R=P(L/2pi*rsquared)

    3. The attempt at a solution
    i keep getting 20856 m as my answer but it is wrng when i entr it i plugged in everything and made sure everything was to the right unit so dont know what is wrong
     
  2. jcsd
  3. Feb 25, 2010 #2

    ehild

    User Avatar
    Homework Helper

    Take care of units. The resistance of the filament is 0.041 ohm, the resistvity is 5.6 x10-8 ohm-meter, and the length is 0.025 m. How could you get such a result for the diameter of a tiny filament??? Show your calculation.

    ehild
     
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