A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle, as shown in the pV diagram in the figure. If the process is carried out in a clockwise sense around the enclosed area, as shown on the figure, then the magnitude of the enclosed area represents
A) the heat that flows out of the gas.
B) the work done on the gas.
C) the heat added to the gas.
D) the work done by the gas.

Question

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle, as shown in the pV diagram in the figure. If the process is carried out in a clockwise sense around the enclosed area, as shown on the figure, then the magnitude of the enclosed area represents 
A) the heat that flows out of the gas. 
B) the work done on the gas. 
C) the heat added to the gas. 
D) the work done by the gas.

Quizplus · Accepted Answer

The enclosed area of the cycle represents the net work done by the gas according to the first law of thermodynamics. Since the process is carried out in a clockwise sense, the gas is doing work on its surroundings, and hence the work done by the gas is negative. Therefore, the magnitude of the enclosed area represents the magnitude of work done by the gas, which is the correct answer.

A Cyclic Process Is Carried Out on an Ideal Gas