If temperature is the average amount of energy and static pressure is the amount of internal energy, wouldn't the static pressure be the same as the temperature?

  • $\begingroup$ Who says that static pressure is the amount of internal energy? $\endgroup$ – Chet Miller Jul 13 '18 at 0:57
  • $\begingroup$ @ChesterMiller I believe the confusion may arise from the fact that $PV$ is often treated as an energy. This certainly isn't the first time I've heard people call pressure an energy density, so I would definitely appreciate it if you could clarify the difference (assuming one exists). $\endgroup$ – probably_someone Jul 13 '18 at 2:10
  • $\begingroup$ Sorry I can't help there. I have never heard of PV being treated as energy. $\endgroup$ – Chet Miller Jul 13 '18 at 2:50
  • $\begingroup$ Temperature is not (average) amount of energy either. None of the two parameters is equal to some energy. $\endgroup$ – nasu Jul 16 '18 at 19:05

Agree with Chester. Static pressure is not energy. Neither is PV which, in the case of a gas, is simply the product of two state variables. But the integral of PdV (pressure-volume work) and the integral of VdP (flow work) are energy transfers in the form of work. Internal energy is the sum of internal kinetic and potential energies. Temperature is generally considered average translational kinetic energy and does not include internal potential energy which is the energy associated with position or configuration. Bottom line, static pressure is not the same as temperature.

  • $\begingroup$ I should add that, however, the pressure on the walls of a rigid container of a gas is a measure of the average force per unit area that the gas molecules exert on the walls due to collisions. That, in turn, is a function of the average kinetic energy of the molecules. If you raise the temperature of the gas, you increase the static pressure. So static pressure is related to the average translational kinetic energy of the molecules which in turn is related to temperature. You also have what is called a pressure head- which is the potential energy due to the height of a column of fluid. $\endgroup$ – Bob D Jul 16 '18 at 15:43

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