p-V Diagrams
Physics: AQA A Level, topic 11.2.3
Pressure-Volume graphs
A pressure-volume graph is a method of showing gas expansion and compression.
Expansion and compression
- An expansion will have an increasing volume, a compression will have a decreasing volume.
- Isotherms are curved lines of constant temperature.
Isotherms and adiabats
- Isothermal lines and adiabatic lines are both curved lines.
- Adiabatic lines are steeper than isothermal lines.
Types of p-V diagrams
Many quantities are represented on a p-V diagram.
Work
- The work done on a p-V graph is the area under the line.
- If the process is a cycle the work done in the cycle is the area of the loop.
Cycles
- Cycles are closed loops.
- Work is done around a cycle but the internal energy is the same at the start and the end.
Test yourself on p-V Diagrams
Which of these statements about p-V diagrams are true?
What shape are adiabatic lines?
How can the work done on a gas be found from a p-V diagram?
Which of these statements about p-V diagrams are true?
The total internal energy of a system is the same at the start and end of a cycle. How much work has been done?