The gas in a perfectly insulated but flexible container does work at a rate of 13 W. At what rate is the internal (thermal) energy of the gas changing?
A) 13 W
B) 0 W
C) 6.5 W
D) -13 W

Question

Quizplus · Accepted Answer

In an insulated system, no heat is exchanged with the surroundings. According to the first law of thermodynamics, the change in internal energy is equal to the heat added to the system minus the work done by the system. Since no heat is added, the change in internal energy is equal to the negative of the work done, which is -13 W.

The Gas in a Perfectly Insulated but Flexible Container Does