Question

If we wanted to increase the internal energy of the system by 10 J, we could...

A. Add 30 J by heating the system and have the system do 20 J of work.

B. Remove 30 J by cooling the system and have the system do 20 J of work

C.Add 30 J by heating the system and do 20 J of work on the system

D. Remove 30 J by cooling the system and do 20 J of work on the system.

Answer 1

Answer:

A. Add 30 J by heating the system and have the system do 20 J of work.

Explanation:

The equation for internal energy is $\Delta U=Q+W$, where here Q is the heat added to the system (negative if removed from the system) and W is the work done on the system (negative if done by the system). From this is clear that if we add 30J of heat to the system and have it do 20J of work we will have $\Delta U=Q+W=(30J)+(-20J)=10J$.