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We can see that the system in question moves from an initial state to a final state in which it absorbs some heat from the environment and performs some work W on the environment in each of these phases. How many of these systems, as well as their surroundings, can be returned to their previous state? We can conclude that it is not possible in the great majority of circumstances based on well-known examples such as rusting and fermentation. In this section, we’ll look at reversible and irreversible processes.
Reversible process
A reversible process is one that can be stopped and restarted without leaving any traces in its wake. It means that when the reverse process is completed, the system and its surroundings are both returned to their original states. Reversible processes don’t exist, and they’re just idealised versions of real-world processes.
We employ the concept of reversible processes because: a) they are simple to analyse (since the system passes through a sequence of equilibrium states); and b) they serve as benchmarks (idealised models) against which actual processes may be compared.
- Friction
- Unrestrained expansion and compression
- Mixing
- Heat transfer (finite T)
- Inelastic deformation
- Chemical reactions are some of the variables that lead a process to become irreversible.
Processes That Can Be Reversed
Reversible processes can be divided into two categories. There are two types of reversible processes: internal and external. Within the system limits, there are no irreversibilities in an internal reversible process. This states that the system goes through the stage of equilibrium, but then goes through the sme stage again when it return.
To put it another way, we can define a reversible process as a process that can be totally reversed.
There are no irreversibilities in an externally reversible process. We can talk about reservoirs and the system, for example.
If no irreversibilities arise within the system’s limits, the process is internally reversible. A system travels through a succession of equilibrium states in these processes, and when the process is reversed, the system goes through the exact same equilibrium states on its way back to its initial condition.
If no irreversibilities develop outside the system limits during the process, it is said to be externally reversible. Heat transfer between the system and the store is outwardly reversible if the region of contact between them is at the same temperature.
Processes that are completely reversible both outwardly and internally.
Examples: The following are some examples of nearly reversible processes:
(i) Relative motion with no friction.
(ii) Spring expansion and compression.
(iii) Fluid expansion or compression without friction.
(iv) Fluid expansion or compression that is polytropic.
(v) Isothermal expansion or compression is a type of isothermal expansion or compression.
(vi) Electrolysis is a process that involves the use of electricity.
Irreversibility of a Process: Factors to Consider
The first criterion is that there should be no dissipative force, and the second is that the process should take a short period.
An irreversible process, on the other hand, is a thermodynamics process that deviates from equilibrium.
When we talk about pressure, we may say that it happens when the system’s pressure varies and the volume doesn’t have enough time to adjust.
One thing to keep in mind is that even when the process is over, the system and its surroundings do not return to their former state in the spontaneous process.
Irreversible processes are exemplified by the following examples.
(i) Frictional relative motion
(ii) Combustion
(iii) Diffusion
(iv) Free expansion
(v) Throttling
(vi) Electrical current flow across a resistance
(vii) Heat transfer
(viii) Plastic deformation
Differences🡪
Process that can be reversed | Process That Isn’t Reversible |
A perfect procedure | A genuine procedure |
It’s a lengthy procedure. | It is a relatively quick procedure. |
This process is reversible. | This is an irreversible |
In the system, there are infinite alterations. | The system undergoes finite alterations. |
Completion takes an indefinite amount of time. | Completion requires a specific amount of time. |
Between a system’s initial and final states, there is a state of equilibrium | Between a system’s initial and final states, there is no equilibrium. |
An expansion of springs, for example. | Electricity flows through a resistance, for example. |
Conclusion:
The irreversible process is described as being in quasi-static mode, meaning that the change is expected to occur at a very slow rate. Reversible processes don’t exist, and they’re just idealised versions of real-world processes. There are no irreversibilities in an externally reversible process. We can talk about reservoirs and the system
