## Work of expansion sign

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

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Gabrielle Schwab 1G
Posts: 26
Joined: Fri Sep 25, 2015 3:00 am

### Work of expansion sign

Can someone explain to me conceptually why work of expansion of a gas is negative? If a gas is expanding isn't it doing work on its surroundings so shouldn't it be positive?

Anthony Rosas 2K
Posts: 14
Joined: Fri Sep 25, 2015 3:00 am

### Re: Work of expansion sign

If a gas is expanding, you can imagine the gas in a chamber pushing on the piston that is lid to the chamber. Since the gas is pushing the lid up, it is using energy. When the gas uses energy it is also losing total energy so the work done by the gas is negative.

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