Question

A student is asked to sketch a pV diagram for a gas that goes

through a cycle consisting of (a) an isobaric expansion, (b) a

constant-volume reduction in temperature, and (c) an isothermal

process that returns the gas to its initial state. The student draws

the diagram shown in FIGURE Q18.12. What, if anything, is wrong

with the student’s diagram?

Short answer

Figure: The pV diagram drawn by the student

In the above figure, line-$a$is representing the isobaric process, line-$b$is representing isochoric process and the line-$c$is representing isothermal process.The isochoric and isobaric process are constant volumes and are represented by straight lines in pV diagram. So, the line a and b drawn by the student aren't wrong. But, the line c isn't drawn correctly. Because, curved line represnts the isothermal process in pV diagram.

Step-by-step solution

What's wrong

Figure: The pV diagram drawn by the student

In the above figure, line-$a$is representing the isobaric process, line-$b$is representing isochoric process and the line-$c$is representing isothermal process.The isochoric and isobaric process are constant volumes and are represented by straight lines in pV diagram. So, the line a and b drawn by the student aren't wrong. But, the line c isn't drawn correctly. Because, curved line represnts the isothermal process in pV diagram.

Correction

The above figure is showing the right way to draw isothermal line c.