Why Is Entropy Considered a State Variable?

  • Thread starter Thread starter bradcliu
  • Start date Start date
  • Tags Tags
    Entropy Thinking
AI Thread Summary
Entropy is classified as a state variable because it depends only on the current state of a system, not on the path taken to reach that state. This allows for the calculation of entropy changes using reversible processes, even when dealing with irreversible processes in real systems. The discussion highlights that while a system can return to a tidy state, the overall entropy of the universe increases, illustrating the second law of thermodynamics. Understanding this distinction clarifies why entropy can be treated as a state variable despite the complexities of real-world processes. The conversation emphasizes the importance of grasping these fundamental concepts in thermodynamics.
bradcliu
Messages
1
Reaction score
0
Hi,

My name is Brad and I am a graduate electrical engineering student. Recently I wanted to go back and review and patch some holes in my head about fundamentals of physics. Therefore, I went back to my textbook Physics for Scientists and Engineers with Modern Physics by Serwey and Jewett, 7th ed. I wanted to understand a few questions I had about thermodynamics from years ago, and more specifically, about entropy.

In the text, it states that entropy is a state variable; therefore, we can find some path of reversible process that leads from one state to the next to calculate it. It never stated why it is a state variable or why the reversible path will work for irreversible or real processes. I can certainly calculate it. However, my understanding about this particular section is frustratingly vague. Please enlighten me Q_Q... Thank you.

Brad
 
Science news on Phys.org


i guess entropy of the total universe if not reversible, but entropy of a particular system is reversible.

so if you made your desk messy, you can make it tidy again in a completely reversible fashion, but in the process introducing more entropy into the universe.
 

Thread 'Condensate rate of water for an air conditioning cooling coil'

I need to calculate the amount of water condensed from a DX cooling coil per hour given the size of the expansion coil (the total condensing surface area), the incoming air temperature, the amount of air flow from the fan, the BTU capacity of the compressor and the incoming air humidity. There are lots of condenser calculators around but they all need the air flow and incoming and outgoing humidity and then give a total volume of condensed water but I need more than that. The size of the...
View full post »
Thread 'Why work is PdV and not (P+dP)dV in an isothermal process?'

Thread 'Why work is PdV and not (P+dP)dV in an isothermal process?'

Let's say we have a cylinder of volume V1 with a frictionless movable piston and some gas trapped inside with pressure P1 and temperature T1. On top of the piston lay some small pebbles that add weight and essentially create the pressure P1. Also the system is inside a reservoir of water that keeps its temperature constant at T1. The system is in equilibrium at V1, P1, T1. Now let's say i put another very small pebble on top of the piston (0,00001kg) and after some seconds the system...
View full post »

Similar threads

I Elementary Ideas About Entropy -- Is this textbook example correct?
Replies
16
Views
2K
B Entropy change for reversible and irreversible processes
Replies
12
Views
2K
Show that entropy is a state function
2
Replies
57
Views
7K
Why does the entropy of a closed system remain constant in a reversible process?
Replies
10
Views
3K
I Entropy change due to heat transfer between sources
Replies
15
Views
3K
Why is entropy a state variable even for irreversible path?
Replies
2
Views
2K
I How can the maximum entropy and minimum energy principles be physical?
Replies
13
Views
3K
Entropy generation during irreversible isothermal expansion
Replies
21
Views
5K
I Irreversible adiabatic processes & entropy change (clarification needed)
Replies
22
Views
5K
Why Is Understanding Entropy So Challenging?
Replies
19
Views
7K

Hot Threads

Recent Insights

Back
Top