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Isochoric process
Intermediate
Constant volume, no work.
Key relation
Q = nC_vΔTConstant volume: no work is done, so Q = ΔU = nCvΔT. A vertical line on the PV diagram.
Worked example
Heating gas in a sealed rigid can.
Common mistake
Pressure rises with temperature.
In more detail
An isochoric process occurs at constant volume, so no work is done. All heat added increases the internal energy and temperature.
Real-world uses
- Heating a gas in a sealed container is isochoric.
- Pressure cookers heat food with little volume change.
- Heating gas in a sealed rigid container is an isochoric process, in which all the heat goes into raising the internal energy.
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Frequently asked questions
Is work done in an isochoric process?
No. Work requires a volume change.
What happens to pressure?
It rises with temperature, as in a sealed cooker.
Why is no work done at constant volume?
Work requires a change in volume, so with the container fixed, the gas does not push anything.
Related topics in Heat & Thermodynamics
Isothermal process · Adiabatic process · Isobaric process · Cyclic process · Heat capacities C_p and C_v · Ratio of specific heats