# Understand Irreversible & Reversible Processes - Intro to Thermo of Materials

• asdf1
In summary, the conversation discussed the concept of reversible and irreversible processes, with an explanation of how a reversible process is the most ideal state that can be achieved. The conversation also touched on the relationship between work and 2PV, with the conclusion that work is determined by the area under the curve on a P-V diagram. Finally, the question was answered and the topic was fully understood.

#### asdf1

I'm reading the book, "Introduction to the Thermodynamics of Materials" (4/e) by David R. Gaskell. There's a section on pg42 explaining irreversible and reversible process, but I have no clue what the point is... Can someone explain it, please?

I really doubt your going to get an answer. You probably should copy down whatever is troublesome for you and post it here.

Reversible process = no entropy production. Or to put it another way, you can turn the process around and go back to the exact same condition that you started with. You can think of it as the process that will be the best (theoretically) you can hope for. A reversible process means that to go from state 1 to 2, the process has to happen very slowly so that equilibrium is reached at every small step.

does the work always equal 2PV? I think that's what the textbook is trying to say...

Work is the area under the curve on a P-V diagram.

asdf1 said:
does the work always equal 2PV? I think that's what the textbook is trying to say...

In order for work to be done, there must be a change in volume. Because of this, 2PV doesn't really mean anything. Take a reversible process at constant pressure. Imagine a piston-cylinder set up. The volume is slowly increased as to keep the process reversible and to keep pressure constant. Now, if you draw the process on a P-v diagram, it will be a straight (horizontal) line. The work can be calculated by integrating [or since its a rectangle, P(v2-v1)].

:) i understand now~
thanks!

## 1. What is the difference between reversible and irreversible processes?

Reversible processes are those that can be reversed by a small change in their conditions, such as temperature or pressure, without any loss of energy. Irreversible processes, on the other hand, involve a loss of energy and cannot be reversed by small changes in conditions.

## 2. Why is understanding irreversible and reversible processes important in thermodynamics?

Understanding these processes is crucial in thermodynamics because it helps us predict how a system will behave and how much energy will be transferred. It also allows us to design systems that are more efficient and to analyze the limitations of a system.

## 3. What are some examples of irreversible processes?

Some examples of irreversible processes include combustion, heat transfer through a temperature difference, and chemical reactions. These processes involve a change in the system that cannot be undone without an external force or energy input.

## 4. Can a reversible process ever occur in real life?

In theory, a reversible process can occur in real life, but in reality, it is difficult to achieve. This is because real-world systems are always subject to some degree of friction, which results in energy loss and irreversible processes.

## 5. How do we calculate the efficiency of a reversible process?

The efficiency of a reversible process is calculated by dividing the work output by the total energy input. In other words, it is the ratio of the useful work produced to the total energy consumed. The higher the efficiency, the more efficient the process is at converting energy into work.