Work in a PV Curve: Is the Work Done 0?

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In a closed thermodynamic cycle, the work done is represented by the area enclosed by the Pressure-Volume curve. While it may seem that the work done is zero since the system returns to its initial state, this is not always the case. If the work from state 1 to state 2 is significantly greater than the work from state 2 back to state 1, the cycle can produce net work. This situation typically arises when the system experiences different loads at various points in the cycle. Thus, a closed cycle can indeed perform work despite returning to its original state.
gabdolce
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Hey all,

In one of my textbooks, there is a passage in the thermodynamics section that states that:

For a closed cycle where the system returns to its initial state, the work done is the area enclosed by the curve (when looking at a Pressure-Volume graph).

Shouldn't the work done by this process be a total of 0 instead?

Thanks in advance.
 
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Not necessarily. A closed cycle can do work. Suppose it cycles between two states. If the work done getting from state 1 to state 2 is much larger than the work done (with the opposite sign of course) from state 2 back to state 1, the cycle will do net work. Note that this does require the system to be under a different load during different parts of the cycle. This changing load is what allows the system to end at the same state that it started while still doing work.
 

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