## internal vs. external pressure

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

bonnie_schmitz_1F
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### internal vs. external pressure

Why is a system is at equilibrium is the internal pressure approximately equal to the external pressure?

Ana Pedreros
Posts: 62
Joined: Fri Sep 28, 2018 12:19 am

### Re: internal vs. external pressure

Yes, when a system is at equilibrium, the internal pressure is approximately equal to the external pressure.

anthony_trieu2L
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

### Re: internal vs. external pressure

Internal pressure is how much change in energy a system undergoes when it expands or contracts. External pressure is the amount of energy that is applied from the outside. At equilibrium, these two are equal

SydBenedict2H
Posts: 60
Joined: Wed Nov 08, 2017 3:00 am

### Re: internal vs. external pressure

If these two were not equal, then they would be attempting to reach a state of equilibrium (being equal). So if you had a closed system with a certain pressure on the inside and a different pressure on the outside, and you suddenly removed whatever was making the system closed rather than open, the pressure would immediately sort itself out as the molecules went from a more pressurized place to less (whether that may be inside or outside of the system).