Difference Between Isothermal and Adiabatic Process with Examples

Understanding isothermal and adiabatic processes is essential in thermodynamics, especially for students preparing for exams like NEET, JEE, or UPSC. Both processes describe how gases behave under different conditions of heat and temperature, but they have key differences.

What is an Isothermal Process?

An isothermal process is a thermodynamic process in which the temperature of the system remains constant throughout.

• Since temperature is constant, internal energy (U) also remains constant.
• Any heat (Q) supplied to the system is completely converted into work (W).

Equation:

Q=WQ = W

Example:

• Slow compression or expansion of a gas in a cylinder with perfectly conducting walls.
• Melting of ice at 0°C where temperature remains constant, but heat is exchanged.

Also Check: Zeroth Law of Thermodnamics 

What is an Adiabatic Process?

An adiabatic process is a thermodynamic process in which there is no heat exchange (Q = 0) between the system and surroundings.

• Temperature does not remain constant, it changes because no heat enters or leaves.
• Work done comes at the expense of internal energy.

Equation:

ΔU=−W\Delta U = -W

Example:

• Sudden compression or expansion of air in a piston-cylinder with insulated walls.
• Atmospheric processes like rising and cooling of air parcels (basis of cloud formation).

Key Differences Between Isothermal and Adiabatic Process