Practice question · Put in order
Arrange these processes in order of increasing work extracted from the same expansion, from least to most.
- Expansion into a vacuum, against zero external pressure
- Expansion against a constant high external pressure
- Reversible expansion, matching the external pressure at every step
- Expansion against a constant low external pressure
Hints
- Work against zero opposing pressure is zero.
- The reversible route is the theoretical maximum.
Show the answer
- Expansion into a vacuum, against zero external pressure
- Expansion against a constant low external pressure
- Expansion against a constant high external pressure
- Reversible expansion, matching the external pressure at every step
Why
Expanding into a vacuum does no work at all. Work grows with the opposing pressure, and the reversible route, where the external pressure matches the internal one at every instant, extracts the theoretical maximum.
Practise The First Law of Thermodynamics
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