CHAP. 1: BASIC TERMS [CONTENTS] 32
Name of the process Constant quantity Symbol
Isothermal temperature [T]
Isobaric pressure [p]
Isochoric volume [V]
Adiabatic heat [ad]
Isentropic entropy [S]
Isenthalpic enthalpy [H]
Polytropic heat capacity [C]Example
In the initial state, a system of a constant volume has a temperature of 300 K and a pressure
of 150 kPa. A certain process takes place in the system, and in the final state the system’s
temperature is 320 K and its pressure is 150 kPa. Does the process take place under a constant
thermodynamic quantity?Solution
The initial and the final temperatures of the system are different. Consequently, the process
cannot be isothermal. Both the initial pressure and the final pressure are identical. In this case
it may be, but not necessarily is, an isobaric process. The specification does not allow us to find
out whether pressure changes in any way in the course of the process. However, the process is
definitely an isochoric one because the system has a constant (i.e. unchanging) volume.1.4.6 Cyclic process
A cyclic process is such at which the final state of the system is identical with its initial state.
In a cyclic process, changes of thermodynamic quantities are zero.
Note:Heat and work are not thermodynamic quantities and therefore they are not zero
during a cyclic process.