The internal energy of a system can increase if A. Heat added to a system exceed
ID: 1479382 • Letter: T
Question
The internal energy of a system can increase if A. Heat added to a system exceeds the work done by the system B. heat leaving system is less than the work done by the system C. Heat leaving system is less than the work done on system D. Both a and b E. Both a and c The internal energy of a system can increase if A. Heat added to a system exceeds the work done by the system B. heat leaving system is less than the work done by the system C. Heat leaving system is less than the work done on system D. Both a and b E. Both a and c The internal energy of a system can increase if A. Heat added to a system exceeds the work done by the system B. heat leaving system is less than the work done by the system C. Heat leaving system is less than the work done on system D. Both a and b E. Both a and cExplanation / Answer
According to the first law of thermodynamic q=U+W
where q - heat added,
U - change in internal energy,
and W - work done.
W can written as Pdv where P is pressure and dv is small change in Volume.
So typically speaking, when you add heat, some amount of heat is going to do work and the rest results change in internal energy. So we particularly can’t say that heat will result in change in internal energy.
But in some cases heat is added at constant pressure. Then you get q=U+PV in this case. When you add heat, it goes in changing PV (to get this we have to integrate the pdv here pdv is constant so it becomes zero) and then it results in change in internal energy.
This is the basic difference between an isochoric and isobaric process. In an isochoric process, volume is constant so W=integral(Pdv)=0 in this case. So heat supplied for isochoric process is q=U+0 = U. So for an isochoric process, the heat added will directly result in change in internal energy. This is why heat added at constant volume is more effective and efficient that heat added at constant pressure
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