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Homework Help: A radiator in a domestic heating system operates at a surface temperat

  1. Nov 14, 2013 #1
    A radiator in a domestic heating system operates at a surface temperature of 55 C.
    Determine the rate at which it emits radiant heat per unit area if it behaves as a black body ?


    why we did not square the temperature
    I mean ( 273 + 55)^4

    please I need your help
  2. jcsd
  3. Nov 14, 2013 #2


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    Because radiation is proportional to the fourth power of the absolute temperature, not the square.

    See the Stefan-Boltzmann Law:

  4. Nov 14, 2013 #3
    my question why in the answer we did not say ( ( 273 + 55)^4 ) not ( 273 + 55) without power 4
  5. Nov 14, 2013 #4
    Maybe same reason they did not put the right order of magnitude for the Stefan-Boltzmann constant (10^(-8) in SI units).
    It may be simply some typo(s). The result seem to be OK. So they did take the fourth power to get that number.
  6. Nov 14, 2013 #5
    It must to make temperature with power 4 ?
  7. Nov 14, 2013 #6
  8. Nov 14, 2013 #7
    ok and this value 5.6697 X 10^-8 for what ?
  9. Nov 14, 2013 #8
    Stefan_Boltzmann constant. Did you even read about Stefan-Boltzmann law of radiation?
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