An external heat source supplies heat to a system at a rate of 187 W as the system does work at a rate of 131 W. At what rate is the internal (thermal) energy of the system changing?
A) -320 W
B) -56 W
C) 190 W
D) 320 W
E) 56 W

Question

Quizplus · Accepted Answer

The rate of change of internal energy in a system is given by the difference between the heat supplied to the system and the work done by the system. Therefore, the rate of change of internal energy is 187 W - 131 W = 56 W.

An External Heat Source Supplies Heat to a System at a Rate