Thermodynamic process
The operation by which a system changes form one state to another is called a process. Whenever a system changes from one state to another it is accompanied by change in energy. In case of open systems, there may be change of matter as well.
The following types of process are known:
1. Isothermal Process
A process is said to be isothermal if the temperature of the system remains constant during each stage of the process. Please note that a process being isothermal does not imply anything about the heat transferred or work done, i.e. heat transfer may take place during an isothermal process. An isothermal process implies that the product of the volume and the pressure is constant for an ideal gas. i.e.
PV = Constant
Isothermal processes can occur in any kind of system, including highly-structured machines, and even living cells. Various parts of the cycles of some heat engines are carried out isothermally and may be approximated by a Carnot cycle.
2. Adiabatic Process
A process is said to be adiabatic if no heat enters or leaves the system during any step of the process. An adiabatic process is also known as isocaloric process which is a thermodynamic process in which no heat is transferred to or from the working fluid.
Conversely, a process that involves heat transfer (addition or loss of heat to the surroundings) is generally called diabatic.
3. Isentropic Process
Isentropic process occurs at constant entropy. For a reversible process this is identical to an adiabatic process if a system has entropy which has not yet reached its maximum equilibrium value, a process of cooling may be required to maintain that value of entropy.
4. Isobaric Process
A process is said to be isobaric if the pressure of the system remains constant during each step of the process. The heat transferred to the system does work but also changes the internal energy of the system.
5. Isochoric (or iso-volumetric) Process
A process is said to be Isochoric (or iso-volumetric)when the volume is held constant. In any Isochoric process, the work done by the system is always zero. For any two dimensional system, the heat energy transferred to that system is absorbed by it as its internal energy. The other name of this process is isometric process. Example – When we heat any empty container, the air inside gains internal energy which can be felt due to increase in pressure and temperature.
Mathematically, δQ = dU. we may say that the system is dynamically insulated, by a rigid boundary, from the environment.
