Why isn't pressure a measure of energy?


The pressure is higher, but the volume is less. The kinetic energy per particle stays the same, when compressing isothermally, there are just more particles per volume to "bounce on the walls", thus the higher pressure. Your higher pressure gas from your drilled cylinder could just do more work per volume, but since there is less volume available the total work stays the same!


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Updated on August 01, 2022


  • bijan
    bijan 10 months

    Hey guys, I'm having a problem in understanding the 1st Law of Thermodynamics.

    If i would increase the pressure of a closed system by compressing a gas in a cylinder isothermal, the 1.Law states, that all the work i put in to the system, i get out by heat.

    So my 2.state would be the gas at the same temperature (same internal energy), but compressed (at a higher pressure).

    But isn't this compressed gas able to do more work, than the not compressed?
    If i drilled a hole in the cylinder my high pressure gas could do some work.

    Where does this energy come from, since all my input energy i put in by work, came out in form of heat?

  • bijan
    bijan over 12 years
    I got it. Thank You! isothermal = constant T = constant p*V ! :)