Phy p4 !

[Arsalan17]

Can someone please tell me when u take work done by the system as positive and when do u take work done on the system as positive ?
Thanx a gazillion !

 

[princesszahra]

i had the same doubt
on the system is always +ve

 

[sse2010]

if Q=U+W then W is work done by the system
if U=Q+W then W is the work done on the system...normally CIE follows the secnd equation dat is U=Q+W

 

[Arsalan17]

i agree but the prob is that sometimes questions have on the system as positive while at other times its the other way round ! Really boggles me =/

 

[princesszahra]

hmm thats y i asked on forums abt it!hope it doent come in exam!

 

[sse2010]

dnt wory...just take it positive!

 

[darkism]

Q +ve when heat is suplied to the syestem..
-ve when het is lost by the system
U +ve for increase in internal energy
-ve for decrease in internal energy
W +ve for work done by the syestem
-ve for work done on the system

 

[Buffer Solution]

Q +ve when heat is suplied to the syestem..
-ve when het is lost by the system
U +ve for increase in internal energy
-ve for decrease in internal energy
W +ve for work done by the syestem
-ve for work done on the system

w is +ve when work is done on the system
and -ve when work done by system mate...

 

[princesszahra]

majority wins!