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Homework Help: Thermodynamics trick question?

  1. Feb 8, 2006 #1
    An empty bottle sits on a windowsill next to a closed window inside a house. The outside and the house are in thermal equilibrium. Yet, the side of the bottle OPPOSITE the window has a higher temp then the side touching the window. How can this be? (Assume nothing is touching the bottle except the windowsill)

    Well, this is what I reasoned so far. There is only 3 ways that heat can be transferred, conduction, convection, and radiation. There is no conduction that is heating the hotter side because there is nothing touching it. It can't be convection b/c the room is in thermal equilibrium with the outside. It has to be the fact that something in side the room is radiating energy onto it.

    Does this make sense? Any other ideas?
  2. jcsd
  3. Feb 8, 2006 #2
    possibly the sun's energy
  4. Feb 8, 2006 #3

    Andrew Mason

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    Is there any air in the room? If there is air in the room, I don't see how the bottle can be at different temperatures and still have the air in the room at thermal equilibrium (which must mean all at the same temperature).

  5. Feb 8, 2006 #4
    This question is bad. (1) How can you assume nothing is touching the bottle except the windowsill, yet its touching the window at the same time. (2) If everything is in thermal equilibrium, as AM has already said, it MUST be isothermal everywhere. (3) The anwser, I think, which is still crap, is that the side touching the window transfers heat due to conduction of the glass, and the side exposed to air gets conduction and convection. So there is a temperature differential. But this is only during the process that it heats up to room temp. Afterwards, it will be isothermal everywhere. Another possibility is that the side nearer the window recieves more solar radiation than the other side. But this would be such a small difference. If the bottle is clear, the radiation should pass through both sides. Eh, I don't know what to tell you.
    Last edited: Feb 8, 2006
  6. Feb 9, 2006 #5
    Ok this is the solution that was given.....

    The bottle has been just turned around.

    How can this even be assumed from the question? It states the room was in thermal equilibrium with the outside therefore via the zeroth law the bottle has to be in thermal equilibrium too!!! I agree this question is horrible.
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