My chemistry book says when occupational is excellent on the system, it is positive. When work is excellent by the system, the is negative.

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My historicsweetsballroom.com book says the opposite. It says that when work is done on the system, the is negative. When job-related is excellent by the system, it is positive.

Why carry out they differ?


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It is simply a matter of convention. It need to be constant throughout.

Case 1: work-related done on the mechanism is positive.

Here the first law is composed as $$ mathrmdU = mathrmdQ + mathrmdW ,. ag1$$

If your frame of referral is "system", climate the work done ~ above the system ($W$) is positive and the warm that is added to the device is additionally positive, which method the adjust in internal power is also positive by very first law the thermodynamics, which way that there is boost in temperature. This appeals to typical sense. Right here positive readjust in inner energy synchronizes to rise in temperature

Case 2: job-related done by the mechanism is positive

Here the very first law is composed as $$ mathrmdU = mathrmdQ - mathrmdW ,. ag2$$

If occupational is applied to the system, $mathrmdW$ hatchet becomes negative making two negatives positive, i m sorry is identical to equation (1) and heat included to the mechanism is still optimistic here. Remainder of the debates follow together above.


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edited Aug 12 "18 at 11:39
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knzhou
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answered Sep 6 "13 in ~ 21:51
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VaidyanathanVaidyanathan
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Taking that in a various sense: chemistry is take away the strategy that you want to produce a brand-new configuration inside the reaction vessel (and input power like heat or such) and also the historicsweetsballroom.com course book is taking about letting the mechanism doing job-related (eg. Burn what is in the reaction vessel).

In both means entropy will certainly be at least equal or positive.


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answered Jul 28 "13 at 6:04
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GerGer
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It"s simply a convention in historicsweetsballroom.com we are more interested in getting some work output say a mechanical maker , engine etc while in chemistry we are more concerned through the internal power things therefore we execute so in both the cases the result is exact same historicsweetsballroom.com situation : du = dq - dw , doing job-related on system increases internal energy as dw = negative for work done on system and vice versa

chemistry case : du = dq + dw ; doing work-related on device will increase the internal power of the device as dw = optimistic which is obvious and also vice versa.

we deserve to take any kind of sign convention in a given problem however we should be regular with that throughout the difficulty to prevent confusion and mistake.

See more: How Many Days Is 11 Years To Days, How Many Days Are In 11 Years


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edited Jun 3 "17 in ~ 3:19
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answer Oct 9 "13 in ~ 10:48
gunjan parashargunjan parashar
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