(a) Many heat engines need both a working fluid and a source of heat, often from a chemical process like combustion. Identify the working fluid and the source of heat for a steam engine like the one in Figure 16.27.?

(b) Many refrigerators require a working fluid and some device that does work. Identify the working fluid and the device that does work for a refrigerator like the one in Figure 16.32B.?

(c) Do all heat engines have a working fluid? Explain.

Figure 16.27