## Work equations

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

Rohan Chaudhari- 1K
Posts: 32
Joined: Fri Sep 29, 2017 7:06 am

### Work equations

Can someone please explain what the different work equations are and when you use them? I'm having trouble identifying which to use in the homework.

Srbui Azarapetian 2C
Posts: 54
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### Re: Work equations

The w=-nRTln(V2/V1) equation is used for reversible expansion. This means that the pressure is continually changing.

The w=-P*deltaV is sued for irreversible expansion. This is in situation with a constant external pressure.

John Huang 1G
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### Re: Work equations

Most of the homework problems will require you to use the work equation for irreversible expansions unless stated otherwise.

If the homework problem asks about reversible, isothermal expansions, then you'll use the reversible equation.

Jana Sun 1I
Posts: 52
Joined: Sat Jul 22, 2017 3:00 am

### Re: Work equations

Also just a heads up, in my discussion section today, my TA mentioned that we don't really need to know/use the reversible equation on the first test, but it's fair game for later tests/midterm.