1. Isobaric process: In an isobaric process pressure of the gas is constant throughout the process. Hence, V/T is constant in an isobaric process. In this process dP = 0.
2. Isochoric Process: A thermodynamic process, in which the volume of gas remains constant, is called isochoric process. In this process, the work done by the system is zero. Thus, the total heat energy absorbed by the system is used to change its internal energy. In this process dV = 0.
3. Isothermal process: In an isothermal process, the temperature of system remains constant throughout the process. Since the internal energy of a system depends only on its temperature, therefore there is no change in internal energy of a perfect gas (ideal gas) in an isothermal process. In this process dU = 0.
4. Adiabatic process: In an adiabatic process, the system neither absorbs heat nor does it reject heat, i.e. in this process there is no heat exchange. In this process dQ = 0.

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