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Heating time near a conductor

  1. Sep 19, 2012 #1
    Hi.

    Practical situation.

    If I have 0.25W of constant Joule loss around a small piece of copper electric conductor, then I would like to find out how much time until a small piece of "Something" (let's say 100mg at 1 kJ/kg*K) around the conductor heats up to 200°C.

    From my calculations, the necessary heat will be Q = Specific heat of the Something (?) * mass of "Something" * (200°C - ambient temp).

    So the amount of time to heat this up is supposed to be Q/0.25W. Am I right?

    Or is there any other delay or heat loss that won't go into heating the "Something" to 200C? :shy:
     
  2. jcsd
  3. Sep 19, 2012 #2

    mfb

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    Staff: Mentor

    If your system "conductor+something" is isolated from the environment and the heat capacity of the conductor is negligible, t=Q/0.25W. A real setup will heat the environment, too, and it will need longer to heat something.
     
  4. Sep 19, 2012 #3
    Heat capacity for the conductor (copper) is 0.385. I would like to take it into account, but how?
     
  5. Sep 19, 2012 #4

    mfb

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    Staff: Mentor

    Just add the heat capacity (specific heat capacity * mass) to the other one. If the heating process is very quick, your conductor will have a higher temperature than the "something", and your estimate will be a bit off - you would need more data to account for that.
     
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