A reversible polytropic process can be described by
PVn = constant
Polytropic Process Overview
In thermodynamics, a polytropic process is a generalized thermodynamic process that can be used to describe many different types of processes, including isobaric, isochoric, isothermal, and adiabatic processes.
Polytropic Process Definition
A polytropic process is defined by a simple mathematical relationship between pressure (P) and volume (V). For a reversible polytropic process, this relationship is expressed by the equation:
\[PV^n = \text{constant}\]
Let's break down the components of this equation:
- \(P\): Represents the absolute pressure of the gas or system.
- \(V\): Represents the volume of the gas or system.
- \(n\): Is known as the polytropic index or exponent. This value can be any real number and determines the specific type of thermodynamic process.
- \( \text{constant}\): Indicates that the product \(PV^n\) remains unchanged throughout the process.
Polytropic Index Significance
The value of the polytropic index, \(n\), is crucial as it dictates the characteristics of the process. Different values of \(n\) correspond to specific common thermodynamic processes:
| Value of \(n\) | Type of Process | Equation Form |
|---|---|---|
| \(n = 0\) | Isobaric Process (Constant Pressure) | \(P = \text{constant}\) |
| \(n = 1\) | Isothermal Process (Constant Temperature) | \(PV = \text{constant}\) |
| \(n = \gamma\) (ratio of specific heats, \(C_p/C_v\)) | Adiabatic Process (No Heat Transfer) | \(PV^\gamma = \text{constant}\) |
| \(n = \infty\) | Isochoric Process (Constant Volume) | \(V = \text{constant}\) |
This flexibility makes the polytropic process equation a powerful tool for analyzing various thermodynamic systems.
Reversible Polytropic Process Equation
The question specifically asks for the description of a reversible polytropic process. The equation \(PV^n = \text{constant}\) accurately describes such a process. A reversible process is an idealized process that can be reversed without leaving any trace on the surroundings, often implying slow, quasi-static changes and no dissipative effects like friction.
Therefore, among the given options, the equation \(PV^n = \text{constant}\) correctly represents a reversible polytropic process.
Important Questions from Thermodynamics System and Processes
- In a polytropic process described by $PV^n = C$, if the polytropic index $n$ is equal to zero, then the process is characterized by constant
Why do particles in liquid water at 0°C have more energy as compared to particles in ice at the same temperature?
Choose the INCORRECT option for the process and its work done (W) and heat transfer (Q) relations.
For a closed system. identify the processes where the following quantities are zero.
1. Heat
2. Work done
3. Internal Energy
Identify the CORRECT statement with respect to the magnitudes of different quantities for different thermodynamic processes.
