## Work equation

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

Netpheel Wang 4L
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

### Work equation

How do you differentiate which work equation to use?

Laura Gong 3H
Posts: 89
Joined: Fri Sep 28, 2018 12:26 am
Been upvoted: 1 time

### Re: Work equation

One is used when the system is at constant pressure (irreversible expansion) (w=-pdeltaV) and the other is used when pressure is not constant (usually isothermal reversible expansion) (w=-nRT*ln(Vf/Vi)).

Samantha Chang 2K
Posts: 69
Joined: Fri Sep 28, 2018 12:17 am

### Re: Work equation

W=-PdeltaV is utilized when pressure IS constant which was shown in lecture through a definite integral because we could factor out the constant of pressure and we are left with the integral dv which just means V2-V1 if we put it into a definite integral. We use the other equation -nRTln(V2/V1) when pressure IS NOT constant, and the derivation of this formula was shown in class today.