q and w

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Lauryn Jordan 1F
Posts: 76
Joined: Fri Sep 29, 2017 7:07 am

q and w

Postby Lauryn Jordan 1F » Sun Jan 14, 2018 4:22 pm

can someone clarify what q and w are as well as how can you tell if they will be positive or negative?

Shawn Patel 1I
Posts: 54
Joined: Thu Jul 27, 2017 3:01 am

Re: q and w

Postby Shawn Patel 1I » Sun Jan 14, 2018 4:27 pm

Hey,
W is work and Q is heat. Work is motion against an opposing force, and heat is the energy transferred as a result of a temperature difference. When work is done on a system, w is positive, and when work is done by the system, w is negative. If heat enters the system, q is positive, and if heat leaves the system, q is negative.

Lauryn Jordan 1F
Posts: 76
Joined: Fri Sep 29, 2017 7:07 am

Re: q and w

Postby Lauryn Jordan 1F » Sun Jan 14, 2018 4:31 pm

soooo my follow up question would be when do you know when work is done on a system vs done by a system?

Kristin Ishaya 1A
Posts: 30
Joined: Fri Sep 29, 2017 7:04 am

Re: q and w

Postby Kristin Ishaya 1A » Sun Jan 14, 2018 4:32 pm

As defined by the textbook, “q is the energy supplied to the system as heat and w is the energy supplied the system as work” (page 278). Basically, q refers to the energy that is transferred or absorbed in a system and work is caused by either an internal or external force that is applied to the system.

Anh Nguyen 2A
Posts: 36
Joined: Fri Sep 29, 2017 7:05 am
Been upvoted: 1 time

Re: q and w

Postby Anh Nguyen 2A » Sun Jan 14, 2018 4:35 pm

q is the energy transferred by heat.
w is the energy transferred by doing work.
If heat has flowed from the system then q is negative. If the system absorbs heat then q is positive.
And for w, if work is done on the system then w is positive, like compressing gas inside an insulated container increases its internal energy. If work is done by the system then w is negative (gas expansion).

Jonathan Tangonan 1E
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

Re: q and w

Postby Jonathan Tangonan 1E » Sun Jan 14, 2018 8:47 pm

Overall, q and w added together make up the internal energy that happens within a system. Q is the energy transferred as heat where a positive q would indicate an absorption of heat while a negative q would indicate a release of heat from the system. A positive w would indicate that work has been done on a system whereas work done by a system would result in a negative w.


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