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Heat flow through aluminium rod

  1. Apr 23, 2017 #1

    em3

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    1. The problem statement, all variables and given/known data
    An Aluminium rod has a diameter of 40mm. and is 750mm long. If the temperature difference between the ends of the rod is 100C .

    Take the thermal conductivity of Aluminium to be 235 Wm-1K-1



    2. Relevant equations
    k * A * ΔT / L

    3. The attempt at a solution
    235 * 0.097 m * 100 / 0.75

    The answer is supposed to be 39.4 Js-1 but I can't get it right? So I don't know if I'm doing something wrong, and I've tried so many times. I don't know what I'm doing wrong.
    Thanks
     
    Last edited: Apr 23, 2017
  2. jcsd
  3. Apr 23, 2017 #2

    gneill

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    Staff: Mentor

    Hi em3,

    Welcome to Physics Forums!

    How did you arrive at 0.095 m for the cross sectional area?
     
  4. Apr 23, 2017 #3

    em3

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    40mm. and is 750mm into m, 0.04m and 0.75m. Then did A=2πrL+2πr2

    2 * ∏ * 0.02 * 0.75 + 2∏0.022≈ 0.097



    Sorry, made a typo in first post
     
  5. Apr 23, 2017 #4

    gneill

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    Staff: Mentor

    You want the cross sectional area, not the total surface area.
     
  6. Apr 23, 2017 #5

    em3

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    How do I find that? The question only gives me the diameter and length, no inner or outer diameter.
     
  7. Apr 23, 2017 #6

    gneill

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    Staff: Mentor

    Assume that a rod is a solid cylinder.
     
  8. Apr 23, 2017 #7

    em3

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    Oh ok thanks, I got it. Thanks a lot!!
     
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