Path refers to series of condition changes through which system pass through a method.
Therefore, path refers to loci of different intermediate states approved through by a system during a method. Sequence refers to a usual sequence of process in such a fashion that the first and final states are equal.
Therefore, a cycle is the one in which the process transpire one after other so as to lastly bring system at similar state. Thermodynamic path in cycle is in closed loop form. After occurrence of a cyclic method system shall show no sign of the processes have occurred.
Mathematically, it can be said that the returning integral of any property in a cycle is zero, that is.,
Ф dp = 0, where p is several thermodynamic property.
Thermodynamic process, path and cycle are made known on p-v diagram.
1—2—3—4—1 = Cycle
1—2, 2—3, 3—4 & 4—1 = Path
1—2 & 3—4 = Constant volume processes
2—3 & 4—1 = Constant pressure processes