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What is a Process Path?

Mathematically, a

process path

can be expressed as an equation for P as a function of V.

We can plug this path equation into the integral above in order to determine the

work

done in a

quasi-equilibrium process

Any two states can be connected by an infinite number of different

process paths

.
Some types of

process paths

are common. Others are used as benchmark cases for comparison with real processes. We will consider

isothermal processes

and

polytropic processes

in the following pages.

Lesson
4A Blog

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Lesson 4A: page 17 of 31

When it comes to calculating moving boundary work or PV work, a process path is just the equation for P as a function of V that describes the collection of states that the system passes through during a process.
Once we have P as a function of V, we can plug it into our equation for PV work and we can determine the amount of PV work done during the quasi-equilibrium process.
So, where do we get the process path equation ?
Well, in general, it isn’t easy to obtain the process path.
But the path equation is easy to get for some simple processes.
The first type of process that we will consider is an isothermal process.
The only other type of process that we will consider in this lesson is polytropic processes.
Polytropic processes are a bit more complicated, but they are very useful. You will see why in later chapters.
Flip the page and we will develop the path equation for an isothermal process for an ideal gas.

What is a Process Path?

process path

work

quasi-equilibrium process

process paths

process paths

isothermal processes

polytropic processes

Ch 4, Lesson A, Page 17 - What is a Process Path?