Where do you want to go ?

Definitions of Reversible and Irreversible Processes

What is the maximum efficiency for a heat engine?

To determine the maximum efficiency of a heat engine we need to define an ideal process and determine the efficiency of such a process. The ideal process is called a reversible process.

It is important to realize that reversible processes are ideal processes and no real process is completely reversible. This leads us to the definition of an irreversible process.

Reversible Processes

processes in which both the system and its surroundings can be simultaneously returned to their initial states after the process has been completed.

Irreversible Processes

processes in which the system and its surroundings cannot be simultaneously returned to their initial states after the process has been completed.

Lesson
6D Blog

Confused and have questions? We've got answers. With Chegg Study, you can get step-by-step solutions to your questions from an expert in the field. If you rather get 1:1 study help, try 30 minutes of free online tutoring with Chegg Tutors.

Roll your mouse over this box to close.

Join Learn Thermodynamics Advantage

Download Data Tables
Download Study Aids
Homework problem hints and answers
Get Help from Dr. B in the LT Blog
120 day membership

Click here to Log-In to your LTA account

Get it ALL for $5 US

Lesson 6D: page 2 of 12

In order to determine the maximum efficiency for a heat engine, we need to define some sort of best case or ideal heat engine.
An ideal heat engine is called a reversible heat engine. An ideal heat engine is made up of a series of reversible processes.
Both the system and the surroundings can be simultaneously returned to their initial states after a reversible process.
After an irreversible process, the system and surroundings cannot both be simultaneously returned to their initial states.
It is often easy to return the system to its initial state, but while doing so we often disturb the surroundings by the exchange of heat or work with the system.
In fact, no REAL process is completely reversible.
We can NEVER return the entire universe to the state it was in before any given process took place.
Flip the page to see why all real processes are irreversible.

Definitions of Reversible and Irreversible Processes

Reversible Processes

Irreversible Processes

Ch 6, Lesson D, Page 2 - Definitions of Reversible and Irreversible Processes