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Adiabatic process
Intermediate
No heat exchange.
PV^γ = constNo heat is exchanged: Q = 0, PV^γ = constant and TV^{γ−1} = constant. A gas cools when it expands and warms when compressed.
A bicycle pump heats up while pumping.
Faster than heat can flow.
In more detail
An adiabatic process occurs with no heat exchange. For an ideal gas, compressing it raises its temperature, and expanding it lowers the temperature.
Real-world uses
- Diesel engines ignite fuel by adiabatic compression.
- Bicycle pumps heat up because compression is nearly adiabatic.
- Air rising and cooling as it expands in a mountain updraft behaves almost adiabatically.
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Frequently asked questions
Why does a pump get hot?
Compressing air quickly does work on it, raising its internal energy and temperature.
Does an adiabatic process change entropy?
Not for a reversible adiabatic process, which is also isentropic.
Why does an adiabatic gas get hot when compressed?
No heat leaves, so the work done on it goes entirely into internal energy, raising its temperature.
Related topics in Heat & Thermodynamics
Internal energy · First law of thermodynamics · Isothermal process · Isobaric process · Isochoric process · Cyclic process