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Homework Help: Not sure what the initial temperature is

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

    At what temperature will aluminum have a resistivity that is three times the resistivity of tungsten at room temperature?

    Rt=5.6 X 10^-8 ohm*m (The resistivity coefficient of tungsten at 20 degrees celcius)
    R0=1.59 x 10^-8 ohm*m (The resistivity coefficient of silver at 20 degrees celcius)
    α =3.9 X 10^-3 degrees celsius ^- 1 (Temperature coefficient of resistivity for aluminum)

    ΔT= Tf-Ti

    I am not sure what the initial temperature is, I assume its 20 degrees celcius.

    2. Relevant equations
    Rt = R0 * ( 1 + α * ΔT)




    3. The attempt at a solution

    3Rt = R0 * ( 1 + α * ΔT)


    I get 11.42 degrees celsius which is wrong?
     
    Last edited: Mar 5, 2010
  2. jcsd
  3. Mar 4, 2010 #2

    berkeman

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    Staff: Mentor

    Re: Resistivity

    Could you please define each of the terms that you're using, and include units on everything?
     
  4. Mar 4, 2010 #3
    Re: Resistivity

    Sorry edited
     
  5. Mar 5, 2010 #4

    berkeman

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    Staff: Mentor

    Re: Resistivity

    That helps, but you define Rt as two different things (a bit confusing), and the units of resistivity are not Ohm/m.

    Does the problem define "room temperature"? 20C is a little low for the room temperature number that I usually use...
     
  6. Mar 5, 2010 #5
    Re: Resistivity

    Ok Thank you.
     
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