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Work done or heat released

  1. Nov 19, 2007 #1
    suppose a certain process is carried out on a system which say heats up the system the how do we decide that that's due to work done or heat released.
    for example suppose i put water in an thermally insulated container and shake it and it's temp. increases then is it due to heat or work done
     
  2. jcsd
  3. Nov 19, 2007 #2

    Dale

    Staff: Mentor

    Once the energy is in the form of heat there is no difference in how the heat was initially generated.
     
  4. Nov 19, 2007 #3
    but my book says it's work done and not heat generated
     
  5. Nov 20, 2007 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Heat flow requires a temperature difference. The issue is not "is thermal energy increased?"--of course it is. You can increase internal energy by doing work or by adding "heat". When you shake the water bottle, the increase in temperature is due to the work you've done.
     
  6. Nov 20, 2007 #5
    yes this is what i thought.Also what about this case
    there is a paddle immersed in water fixed within which is connected to a movable block through a fixed pulley When the block moves the temp of the system rises is it work done or heat released .I think work done because the same reason as above .
    Would like to know ur answers
     
  7. Nov 20, 2007 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Sure, that's a similar situation: the temperature increase is due to work done, not "heat" added. In fact, that paddle experiment was used by Joule to first show that mechanical work can be converted to "heat".
     
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