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Homework Help: Temperature to raise resistance

  1. Sep 16, 2010 #1
    1. The problem statement, all variables and given/known data
    A platinum wire is originally at 15 degree Celcius. Find the required temperature to increase its resistance by 3%.

    2. Relevant equations
    R = Ro * [1 + 'a' * (T-To)]
    Ro is initial resistance. To is initial temperature.
    'Temperature Coefficient' 'a' of platinum at room temperature 20 degree celcius is 3.9 * 10^-3

    3. The attempt at a solution
    I don't have an initial resistance to start off with. But I do have the initial temperature and the room temperature, To = 15 and T = 20 degree Celcius.

    Solving for Temperature T = ('a'To + R/Ro) / 'a'
    But I don't have any reference resistance to begin with, how do I solve this?
  2. jcsd
  3. Sep 16, 2010 #2
    [tex] R = R_o[\alpha (T - T_o) + 1][/tex]
    [tex] R = 1.03R_o[/tex]
  4. Sep 16, 2010 #3
    Can you show how you got this by eliminating all the other variables? Even from this simplified form, there isn't an initial resistance to begin with. Unless....

    [tex] R_o = R / 1.03[/tex]

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