States of a thermodynamic system can be changed by interacting with its surrounding through work and heat. When this change occurs in a system, it is said that the system is undergoing a process.
A thermodynamic cycle is a sequence of different processes that begins and ends at the same thermodynamic state.
When the system undergoes change from one state to the other, but its temperature remains constant. Thus, in our example of hot water in a thermos flask, if we remove a certain quantity of water from the flask but keep its temperature constant at 50 degree Celsius, the process is said to be an isothermal process.
The process during which the pressure of the system remains constant is called an isobaric process.
The process during which the volume of the system remains constant is called an isochoric process. The heating of gas in a closed cylinder is an example of an isochoric process.
The process during which the heat content of the system or a certain quantity of matter remains constant is called an adiabatic process. Thus, in the adiabatic process, no heat transfer between the system and its surroundings occurs.
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