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Isobaric process
Intermediate
Constant pressure.
W = PΔVConstant pressure: W = PΔV and Q = nCpΔT. A horizontal line on a PV diagram.
Heating gas in a piston with a freely moving lid.
Most heat goes to expansion work for gases.
In more detail
An isobaric process occurs at constant pressure. The work done is pressure times the change in volume, and heat added goes into both work and internal energy.
Real-world uses
- Heating a gas in an open container is roughly isobaric.
- Cylinders with pistons heated at constant pressure follow this process.
- A gas in a cylinder with a movable piston and constant outside pressure expands at constant pressure when heated.
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Frequently asked questions
How is work calculated?
W = P ΔV for a constant pressure process.
Why is more heat needed than at constant volume?
Because the gas also does work as it expands at constant pressure.
How do I find the work in an isobaric process?
Multiply the constant pressure by the change in volume, which gives the area under the P-V line.
Related topics in Heat & Thermodynamics
First law of thermodynamics · Isothermal process · Adiabatic process · Isochoric process · Cyclic process · Heat capacities C_p and C_v