Entropy: Understanding the Cycle | Thermodynamics

In summary, the conversation discusses the concept of entropy in an isolated system and whether it remains the same or increases in a thermodynamic cycle. It is stated that the entropy of the system will return to its initial value after each cycle, but the overall entropy of the universe can still increase due to work dissipation or heat transfer. There is no upper limit to the amount of entropy that can be created in the universe.
  • #1
Tikkelsen
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I'm having trouble getting my head around entropy. In an isolated system, entropy can only remain the same or increase. Is this the same for a thermodynamics cycle? What I mean is, if I drew a cycle on a PV diagram, would the entropy keep increasing? I can't see how that would work, that would mean I would have infinite entropy if I run the cycle an infinite number of times
 
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  • #2
Thermodynamic entropy is a function of state. Cyclic process returns system into the same state all over again. So the value of entropy returns to the initial value as well.
 
  • #3
Tikkelsen said:
I'm having trouble getting my head around entropy. In an isolated system, entropy can only remain the same or increase. Is this the same for a thermodynamics cycle? What I mean is, if I drew a cycle on a PV diagram, would the entropy keep increasing? I can't see how that would work, that would mean I would have infinite entropy if I run the cycle an infinite number of times


The entropy of the system undergoing the cycle would be the same after every cycle. If you have work dissipation or heat transfer between finite temperature differences then the entropy of the universe increases. So yeah the law of entropy applies perfectly to cycles.
That being said, what's the problem with the entropy increasing without bound if you run the cycle many times? entropy increases or remains the same, there's no upper limit to the amount of entropy that can be created in the universe.
 

1. What is entropy?

Entropy is a concept in thermodynamics that refers to the measure of the disorder or randomness in a system. In simpler terms, it is a measure of how much energy is unavailable for useful work.

2. How does entropy relate to thermodynamics?

Entropy is closely related to the second law of thermodynamics, which states that the total entropy of a closed system will always tend to increase over time. This means that the disorder or randomness in a system will increase over time, and energy will become less available for useful work.

3. What is the relationship between entropy and energy?

Entropy and energy are closely related, but they are not the same thing. Entropy is a measure of the disorder or randomness in a system, while energy is a measure of the ability to do work. As entropy increases, the amount of available energy decreases.

4. How is entropy calculated?

The specific formula for calculating entropy depends on the system in question. In general, it involves taking into account the number of possible microstates (or arrangements) of particles in a system and the energy levels associated with those microstates. The higher the number of possible microstates, the higher the entropy.

5. What are some real-life examples of entropy?

There are many examples of entropy in our daily lives. Some common examples include the spread of heat in a room, the mixing of different substances, and the decay of organic matter. All of these processes involve an increase in disorder and a decrease in available energy, which is a result of the second law of thermodynamics.

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