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Homework Help: Heat exchanged to air on a cylinder problem?

  1. Aug 21, 2007 #1
    1. The problem statement, all variables and given/known data
    If heat is transferred to air inside a cylinder and the volume doubles does the pressure change ?

    2. Relevant equations+ thoughts about the statement
    My thoughts are that energy is given to the air molecules inside the cylinder causing the volume of the air to expand hence the volume double i personally think the pressure stays the same(as the cylinder moves to return the pressure to the original pressure as the heat is transferred) but i am not 100% sure of the relationship here. Can any one shed some light on the situation?

    Thanks i may have a few more queries
  2. jcsd
  3. Aug 21, 2007 #2


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    It is a rather badly worded question, it depends on how much heat.
    I suspect they are trying to say that the volume is free to expand as much as it likes to keep the pressure constant.

    The relationship is the Pressure * Volume is proprtional to Temperature
    If the correct amaount of heat was added to double the temperature and the volume doubled then the pressure would stay the same.
    If a million times as much heat was added and the volume only doubled then the pressure would go up!
  4. Aug 21, 2007 #3
    I thought that myself about the question a little misleading, so volume is proportional to temperature at a constant pressure meaning that if heat is added the volume will increase and the pressure remains constant. Cheers for the quick reply you dont by any chance have any ideas about the other thermofluids question i have asked? It involves a U tube manometer in a wind tunnel another question that i am really struggling to get my head around.
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