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Problem with units for conduction rate?

  1. Aug 13, 2017 at 1:49 PM #1
    1. The problem statement, all variables and given/known data
    Consider the slab shown in Fig. 18-18. Suppose that L 25.0 cm, A 90.0 cm2, and the material is copper. If TH 125 C, TC 10.0 C, and a steady state is reached, find the conduction rate through the slab.

    2. Relevant equations
    Pcond = Kc *A*(TH - TC)/L
    K = 401 W/m*k
    3. The attempt at a solution
    I'm converting degrees celsius to kelvin so that it cancels with the kelvin unit from the conductivity K and I'm getting an answer of 5774W but when I look here

    http://www.chegg.com/homework-help/...0-cm2-material-copper-th-103-c-tc-80-c-q43179
    and here
    http://www.chegg.com/homework-help/...50-cm-860-cm2-material-copper-th-124-q4982672

    they are leaving the degrees in celsius. What's more, the answer in the back of my book matches these answers! How can an answer in celsius over kelvin make any sense!? Is the answer in the back of the book also wrong?!
     
    Last edited: Aug 13, 2017 at 2:11 PM
  2. jcsd
  3. Aug 13, 2017 at 2:03 PM #2

    phyzguy

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    Science Advisor

    When you subtract the two temperatures, the difference between the two temperatures is the same in the Celsius and Kelvin scales. Thus (per degree Kelvin) and (per degree Celsius) give the same answer.
     
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