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Homework Help: Thermodynamics - heat transfer

  1. Jun 19, 2010 #1
    1. The problem statement, all variables and given/known data
    if the temperature of an object changes from 80 to 433 degrees Celsius, but the area and emissivity remains constant, by how much does radiated power increase?


    2. Relevant equations
    P=phi*A*e*T^4


    3. The attempt at a solution
    i tried to do this:
    80^4-433^4. and get the temperature change...but i do not know where to go from here, please if someone could give good explanation about this, i got an exam in 2 days=/..thanks!!=]
     
  2. jcsd
  3. Jun 19, 2010 #2

    rock.freak667

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    Homework Helper

    So the change is E=εA(T24-T14) (remember to change the temperatures to Kelvin).

    Originally the power was E=εAT14

    So what is the ratio of the change in power to the original power?
     
  4. Jun 19, 2010 #3
    so i did this:
    706^4 - 353^4
    =2.329*10^11
    um now how do i find the ratio of the change from this?
     
  5. Jun 19, 2010 #4

    rock.freak667

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    So you have ΔE= εA(2.239x1011)

    Initially E = εAT14

    So get E and just find ΔE/E
     
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