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Homework Help: Finding resistance and temp co-efficient

  1. Feb 24, 2010 #1
    1. The problem statement, all variables and given/known data
    A motor winding has a risitance of 80 ohm at room temperature of 20c before
    switching on to a 230v. after 4 hour run wionfing resistance is 100 ohm
    find the temperature rise if the matrial resistance temperature co-efficient is 1/234.5/c.

    R at 20 = 80 ohm
    R at t = 100 ohm
    alpha =1/234.5

    2. Relevant equations
    R at 20/R at t = R at 0c (1 - at)/ R at 0c (1-at)

    3. The attempt at a solution

    80/100 = 1+0.004264X20/1+0.004264t

    t = 83.630 c

    Rise is t-20 = 83.630-20
    t rise is 63.63 c
  2. jcsd
  3. Feb 24, 2010 #2


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    The rise does not take into acount the initial temperature as if it were in Kelvin it would have been 293.5. The actual result should be 83.63.
  4. Feb 25, 2010 #3

    but solution is right? and answer 83.63 is ok with this statement
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