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Homework Help: Thermodynamics problem over cycles

  1. Feb 3, 2015 #1
    1. The problem statement, all variables and given/known data
    The filament is 30 cm long and has a diameter of 1.5mm. The filament is drawing 15 watts and has an emissivitity of 0.9. The surroundings are at 283 k. Estimate the surface temp of the filament in K.

    2. Relevant equations
    N = Wcycle/Qin, W cycle = Qhot - Q cold.

    3. The attempt at a solution
    I'm not sure how to relate the lengths. I think 0.9= Wcycle/15 watts. But not sure what to do after I find Wcycle. Any help would be appreciated!
  2. jcsd
  3. Feb 3, 2015 #2


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    Staff: Mentor

    Hi Jpcol1990, Welcome to Physics Forums.

    I'm not sure what this Wcycle stuff is about, but shouldn't you be looking at the Stefan-Boltzmann Law for problem involving power, temperature, and emissivity?
  4. Feb 8, 2015 #3
    I figured it out! haha. But thanks for your help, bud.
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