reversible process

[Qinyan Feng 1H]

Hi,

Why can reversible processes do more work than irreversible processes?
I'm confused with this.

Thank you.

[Sunny Xiao 1A]

Reversible processes don't lose energy as heat because they take much longer, and need to "overcome" more external pressure. However, for irreversible processes, some of the energy is lost as heat due to how quickly they happen.

[Triston Dinh 1D]

Less work is done in an irreversible process because the system is pushing against only a constant lower pressure of the surroundings (like 0.5 atm compared to 1.0 atm of the system). However, in a reversible process, the system does work in intervals until the external pressure decreases (from 1 atm --> 0.5 atm) and these intervals of work can be summed up with an integral. For example, you will add up all the times that the system did work on 0.999999 atm, 0.999998 atm, 0.999997 atm, etc.

[Jessica Cornelia Hongarta 1G]

So, for the reversible process, the system is at equilibrium and it expands very slowly, (∆V changes infinitesimally) so the external pressure decreases very slowly. Thus, the system is pushing against external pressure that is equal to the internal pressure. This step is repeated over and over again and the sum of these steps gets us the maximum work done. Meanwhile, for the irreversible system, external pressure is lower than internal pressure. Since the system is pushing against lower pressure, it does less work.

Hope this helps!