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Thermal radiation lab experiment

  1. Dec 1, 2013 #1
    Hi,

    I have to plan and carry out an experiment on thermal radiation as part of my physics lab module. The description of the experiment is as follows: Investigate the radiation from a bulb filament as a function of input power, using a pyrometer to measure the temperature of the filament.

    I'm guessing the purpose of this experiment is to verify the Stefan-Boltzmann law, which states that P=AσT^4 where P is the power radiated from the object, A is the surface area of the object (filament or light bulb?) and T is its temperature in Kelvin, and σ is the Stefan-Boltzmann constant. So, plotting P against T^4, and dividing the gradient of the resultant graph by A should give me a value close to Stefan's constant. But I have 2 questions:

    1) Should I measure the surface area of the bulb, or the filament?
    2) Can I assume input power = P, so that I can calculate the values of P using a multimeter in a circuit?

    Any ideas would be appreciated.
     
  2. jcsd
  3. Dec 1, 2013 #2

    haruspex

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    If you kept the filament the same but made the bulb ten times the diameter, would the power from it change?
    Seems fair.
     
  4. Dec 1, 2013 #3
    I don't think it would.
     
  5. Dec 1, 2013 #4

    haruspex

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    Right, so which area matters?
     
  6. Dec 1, 2013 #5
    The surface area of the filament.
     
  7. Dec 1, 2013 #6

    haruspex

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    Yes.
     
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