## Reversible and Irreversible

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Fiona Latifi 1A
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Joined: Sat Sep 14, 2019 12:16 am

### Reversible and Irreversible

What are reversible and irreversible processes? What do reversible expansion and irreversible expansion mean?

MingdaH 3B
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### Re: Reversible and Irreversible

From our textbook:"in thermodynamics, a reversible process is one that can be reversed by an infi- nitely small change in a variable (an “infinitesimal” change). For example, if the external pressure exactly matches the pressure of the gas in the system, then the piston moves in neither direction. If the external pressure is increased infinitesimally, then the piston moves in. If, instead, the external pressure is reduced infinitesimally, the piston moves out. Expansion against an external pressure that differs by a measurable amount from the pressure of the system is an irreversible process in the sense that an infinitesimal change in the external pressure does not reverse the direction of travel of the piston"

805307623
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Joined: Fri Aug 09, 2019 12:17 am

### Re: Reversible and Irreversible

Reversible expansion: The state starts off where gas pressure = external pressure. Then, an external force decreases the outside pressure, making the gas slightly before reaching a new equilibrium state. This procedure is repeated as many times as needed to reach the desired pressure.
Irreversible expansion: This occurs when the outside pressure decreases instantaneously and dramatically, and the gas expands until it reaches equilibrium.

Matt F
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### Re: Reversible and Irreversible

In other words, the process is reversible since the system is at equilibrium, correct? So irreversible would mean the change is large enough to not maintain equilibrium?

chari_maya 3B
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### Re: Reversible and Irreversible

The book states:
"work done during a reversible expansion of a gas is the maximum expansion work possible". Why is this true?

Nikki Razal 1L
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### Re: Reversible and Irreversible

to add, i think dr. lavelle stated that if a system is at equilibrium, it is a reversible process