What is Reversible processes: Definition and 21 Discussions

In thermodynamics, a reversible process is a process whose direction can be reversed to return the system to its original state by inducing infinitesimal changes to some property of the system's surroundings. Throughout the entire reversible process, the system is in thermodynamic equilibrium with its surroundings. Having been reversed, it leaves no change in either the system or the surroundings. Since it would take an infinite amount of time for the reversible process to finish, perfectly reversible processes are impossible. However, if the system undergoing the changes responds much faster than the applied change, the deviation from reversibility may be negligible. In a reversible cycle, a cyclical reversible process, the system and its surroundings will be returned to their original states if one half cycle is followed by the other half cycle.

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1. I Is this transformation irreversible?

This is a cyclic transformation. Is it safe to say thay it's irreversible because if you reverse it, it means I could extract an amount of heat from a cold reservoir and move it into a hotter reservoir with no other effect?
2. Thermodynamics of chemical reactions

In chemical reactions generally ΔG < 0 , but if we were to consider a reversible path between pure reactants and products at 1 bar pressure , shouldn't the ΔG = 0 for every reaction ? and if it is due to non-pv work , I don't see any non pv work being done in reactions happing in a closed...
3. To find total work done from multiple reversible processes

The question is given in 3 parts. For first part, process is isochoric so Work done=0. We know here that at end of the process (a), T2=T1 while V remains constant (we can take it as V1) so P2=2P1. For second part, process is isothermal so T is constant. At end of process we reach P1 again from...
4. Work done by irreversible and reversible processes

I am not able to follow the derivation of work done in a reversible and irreversible process as I don't get why the work done should be different in the two processes. a reversible process is said to be a process that occurs infinitesimally slowly and an irreversible process goes from initial to...
5. Reversible processes need to be ONLY isothermal or adiabatic?

My question is: Do ALL the reversible process need to be composed of ONLY isothermal and adiabatic transformations? Carnot cycle satisfy this, but what other cycle would be also reversible? I know that for a process to be reverisble it has to be almost-static, have no dissipative force, and no...
6. Irreversible quasi-static processes?

I read an example where if I go from initial to final state extremely fast (gas inside a piston cylinder assembly) , the gas inside it will be very unhappy, its not going to stay in equilibrium, parts of the system are going to be at different pressure and parts of it at something other...
7. Thermal Physics: Reversible processes

Hi all, I have been having some issues trying to show that a reversible expansion of gas does not create new entropy. Assistance is greatly appreciated! So suppose that a gas expands reversibly as shown below at fixed temperature At fixed temperature, internal energy doesn't change so...
8. B Reversible Processes Explained: Entropy, Time, & More

Can someone explain to me what a reversible process means, because I am not sure I really understand. Intuitively it should be a process that should work both ways, but I am not sure I understand how it is related to entropy (the change of entropy should be 0, but I am not sure I understand...
9. Quasi-static and reversible processes in thermodynamics

Too much confusion in my head about these concepts... Is every reversible process quasi static? If not, what are some examples? If process is irreversible then it doesn't need to be non quasi-static, I understand that. (eg. free expansion of the gas) Can irreversible process be quasi static...
10. Question about Reversible Engines and Carnot Efficiency

Homework Statement I have a question regarding heat engines that cropped up whilst I was doing a practice question. I will summarise the results I obtained for the previous parts of the question so as to save your time. The highlighted parts of the image are where I am having some issues. I...
11. Reversible Work and Irreversibility

I am trying to grasp the concepts of reversible work, irreversible work and irreversibility.(Last one is the difference between them if i am not mistaken.) Let us consider a rigid and evacuated container at volume V. Then, a valve opens and athmospheric air (P0, T0 is filling the tank. The wall...
12. Entropy change in irreversible processes

The equation for entropy S=delta(Q)/T is derived from reversible processes such as Carnot cycle. The delta(Q) in the equation is the reversible heat added or taken out from the system. So, why is this equation valid in the case of processes like cooling of a body which is irreversible?
13. Reversible Processes: Quasi-Static Adiabatic Expansion from Callen Ch. 4

I'm working from Callen ch. 4: Consider a monatomic ideal gas in a cylinder fitted with a piston.The walls of the cylinder and the piston are adiabatic. The system is initially in equilibrium, but the external pressure is slowly decreased. The energy change of the gas in the resultant...
14. The importance of reversible processes(?)

In thermodynamics(at least in classical thermodynamics),the idealization of reversible processes is used time and again.Can we say it is central to thermodynamics? I mean can we say it is so important that if we can't find a reversible counterpart for an irreversible process,then the existence...
15. Don't reversible processes always do the most possible work?

I am trying to teach myself the basics of thermodynamics using a book I bought from a university book store. My question relates to the amount of work done by reversible vs irreversible processes. An example in the book (Chemical Principles by Atkins & Jones) reads the following: "A cylinder...
16. Justification of generalisation from reversible processes to all procesess

Hi all, I've been having some difficulty understanding the derivation of the Fundamental Theorem of Thermodynamics, dU=T \ dS-P \ dV. The derivation, which can be found at Wikipedia (http://en.wikipedia.org/wiki/Fundamental_thermodynamic_relation) first starts with the universal First Law...
17. Understanding Carnot's Cycle & Reversible Processes

Why is it so that along with reversible isothermic processes , reversible adiabatic processes must be taken up to complete carnot's cycle?
18. Reversible Processes: Isothermal to Adiabatic Transition

The problem: A red-hot 2.00 kg piece of iron at temperature t1=880k is thrown into a huge lake whose temperature is t2=280K. Assume the lake is so large that its temperature rise is insignificant. The book says that this process is irreversible. Why? I have another question. In a reversible...
19. Thermodynamics: Reversible Compression of Solid Volume V

Hi, this concerns thermodymanics. A block of volume V is reversibly compressed from pressure P1 to pressure P2 isothermally at temperature T. It goes on to ask about the heat expelled, but that's not my question. It is a solid, obviously not an ideal gas, so I'm sure the internal energy...
20. Reversible processes and carnot cycle

i want to ask why heat transfer is considered ti be an irreversibility and why in carnot carnot cycle heat addititon is at constant temperature to make this process reversible
21. Thermodynamics, isentropic and reversible processes

Hi, I have some questions regarding thermo: 1) Does an isentropic process have to be a quasistatic one? What is the relation between equilibrium and reversibilty? 2) Naturally, there are revesible processes involving control volumes. A gas can go through an isentropic process in a reversible...