National Council of Examiners for Engineering and Surveying (NCEES) Fundamentals of Engineering (FE) Other Disciplines Practice Exam

An adiabatic process is characterized by the absence of heat transfer to or from the system. This means that all changes in the internal energy of the system are due solely to work done on or by the system. An isentropic process, on the other hand, is a specific type of adiabatic process that is also reversible and involves no change in entropy.

The correct answer distinguishes itself by highlighting that while both adiabatic and isentropic processes are defined by the lack of heat transfer, isentropic processes also maintain the condition of reversibility, implying that the process can be returned to its initial state without any net change in the system or surroundings. The assertion that isentropic processes are not reversible is inaccurate; it is the opposite, as they are defined by their reversible nature.

Understanding these definitions is crucial because many thermodynamic analyses assume idealized processes, and recognizing the distinctions between adiabatic and isentropic behaviors aids in accurately modeling such systems.