Irreversible System + system at equil

[Ivy Nguyen 3I]

Hi! Todays lecture was a little harder to follow for me so could anyone explain irreversible systems and systems at equilibrium at all? Anything helps! thanks

[Kayla Arellano 1K]

Hi! Todays lecture was a little harder to follow for me so could anyone explain irreversible systems and systems at equilibrium at all? Anything helps! thanks

The system at equilibrium is a reversible process where the volume changes in very small steps and pressure is not constant. In the diagram Dr. Lavelle drew in class, it was a closed system with a small opening to allow gas to come in and out of the system so the external pressure can remain approximately equal to the internal pressure as the volume makes small changes. Mathematically, work can be represented by the infinite sum of -(pressure*change in volume) which can be rewritten as the -(integral of external pressure*derivative of volume). When systems are not set up at equilibrium, their process is not reversible and the external pressure has to be lower than the internal pressure. In the diagram drawn in lecture, it was also a closed system with pins holding down the piston and no opening so the pressure remains constant in the system. Because the system is pushing against a lower external pressure, less work is done and it occurs at a faster pace than a system at equilibrium. Mathematically, work can be represented by -(pressure*integral of derivative of volume) which can be simplified to -(pressure*change in volume). Hope this helps!

[Alyssa Cua 2J]

Hi! Todays lecture was a little harder to follow for me so could anyone explain irreversible systems and systems at equilibrium at all? Anything helps! thanks

The system at equilibrium is a reversible process where the volume changes in very small steps and pressure is not constant. In the diagram Dr. Lavelle drew in class, it was a closed system with a small opening to allow gas to come in and out of the system so the external pressure can remain approximately equal to the internal pressure as the volume makes small changes. Mathematically, work can be represented by the infinite sum of -(pressure*change in volume) which can be rewritten as the -(integral of external pressure*derivative of volume). When systems are not set up at equilibrium, their process is not reversible and the external pressure has to be lower than the internal pressure. In the diagram drawn in lecture, it was also a closed system with pins holding down the piston and no opening so the pressure remains constant in the system. Because the system is pushing against a lower external pressure, less work is done and it occurs at a faster pace than a system at equilibrium. Mathematically, work can be represented by -(pressure*integral of derivative of volume) which can be simplified to -(pressure*change in volume). Hope this helps!

This was super helpful! Thanks so much for this explanation.