/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 12 Show how the polytropic exponent... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Show how the polytropic exponent \(n\) can be evaluated if you know the end state properties, \(\left(P_{1}, V_{i}\right)\) and \(\left(P_{2}, V_{2}\right)\).

Short Answer

Expert verified
The polytropic exponent \(n\) can be evaluated by rearranging the polytropic process equation and solving for \(n\). Thus, \(n = \log \left(\frac{P_{1}*V_{1}}{P_{2}*V_{2}\right)\).

Step by step solution

01

Identify given values

The initial and end states are given by \(\left(P_{1}, V_{1}\right)\) and \(\left(P_{2}, V_{2}\right)\). These represent initial pressure and volume, and final pressure and volume, respectively.
02

Apply the polytropic formula

In a polytropic process, the equation: \(P*V^n = C\) is used. We apply the formula for both states, giving us \(P_{1}*V_{1}^{n}=C\) and \(P_{2}*V_{2}^{n}=C\).
03

Set the two equations equal

Since \(P_{1}*V_{1}^{n}=C\) and \(P_{2}*V_{2}^{n}=C\), given that \(C\) is constant, we can set the two equations equal to each other: \(P_{1}*V_{1}^{n}=P_{2}*V_{2}^{n}\).
04

Solve for \(n\)

We rearrange the equation to isolate \(n\). This is done by dividing both sides by \(P_{1}*V_{2}^{n}\) and taking natural logarithms to remove the power. Thus \[\frac{P_{1}*V_{1}}{P_{2}*V_{2}} = 10^n\] so we get \[n = \log \left(\frac{P_{1}*V_{1}}{P_{2}*V_{2}\right) \] .

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Polytropic Process
A polytropic process is a type of thermodynamic process that can describe a wide variety of changes that a gas can go through. It's characterized by the relationship between pressure \(P\), volume \(V\), and an exponent \(n\), which remains constant for a particular process. This process is represented by the equation \(P V^n = C\), where \(C\) is a constant specific to the given process.

Understanding the polytropic process is critical in many fields such as engineering and physical sciences, where gases undergo transitions that don't neatly fit into simpler isothermal or adiabatic processes. For instance, during a polytropic process, heat transfer can occur, which differentiates it from adiabatic processes where there is no heat transfer involved. Additionally, the value of the polytropic exponent \(n\) can provide insights into the nature of the transformation: if \(n = 0\), the process is isobaric (constant pressure); if \(n = 1\), it is isothermal (constant temperature); and if \(n = \infty\), it approaches an isochoric process (constant volume). Knowing the value of \(n\) allows us to interpret the relationships and energy transformations that occur during the polytropic process.
Thermodynamics
Thermodynamics is a fundamental branch of physics that deals with the study of heat, work, and energy. It lays out a framework of rules and equations that describe how different forms of energy are transferred and transformed in a system. The field of thermodynamics is built on four key laws, which define how energy is conserved and how entropy, a measure of disorder, tends to increase over time.

In the context of the polytropic process, thermodynamics provides the necessary principles to understand how energy is converted from one form to another as the gas expands or compresses. When looking at polytropic processes, we often use the concepts of internal energy, enthalpy, and entropy to describe the state of the system. These concepts help to clarify how the system's temperature, pressure, and volume change in relation to one another, and they are crucial for solving complex problems, such as calculating the work done by or on the gas.
Pressure-Volume Relationship
The pressure-volume relationship, often expressed as \(PV\) relationship, is an important concept in thermodynamics that describes how the pressure of a gas is related to its volume. These relationships can be linear or non-linear, depending on the type of thermodynamic process that a system undergoes. In a polytropic process, this relationship is governed by the equation \(PV^n = C\), where the constant \(n\) defines the nature of the process and can vary based on the specific heat properties of the gas involved.

To solve problems involving the pressure-volume relationship in a polytropic process, one must understand how to manipulate the polytropic equation. For example, given two sets of pressure and volume data, you can deduce the value of \(n\) by comparing the states. This is essentially finding an unknown exponent based on known quantities, a fundamental mathematical concept that applies to a variety of real-world situations, such as calculating engine efficiency or the performance of heating and cooling systems. By mastering the pressure-volume relationship, students can better comprehend various physical phenomena they encounter in the field of thermodynamics.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

A cylinder containing 2 lbm of ammonia has an externally loaded piston. Initially the ammonia is at \(280 \mathrm{lbf} / \mathrm{in}^{2}, 360 \mathrm{F}\). It is now cooled to saturated vapor at \(105 \mathrm{F}\), and then further cooled to \(65 \mathrm{F}\), at which point the quality is \(50 \%\). Find the total work for the process, assuming a piecewise linear variation of \(P\) versus \(V\)

A cylinder having an initial volume of \(100 \mathrm{ft}^{3}\) contains 0.2 lbm of water at 100 F. The water is then compressed in an isothermal quasiequilibrium process until it has a quality of \(50 \%\). Calculate the work done in the process assuming water vapor is an ideal gas.

A substance is brought from a state of \(P_{1}, v_{1}\) to a state of \(P_{2}, v_{2}\) in a piston/cylinder arrangement. Assume that the process can be approximated as a polytropic process. Write a program that will find the polytropic exponent, \(n,\) and the boundary work per unit mass. The four state properties are input variables. Check the program with cases that you can easily hand calculate.

Two kilograms of water are contained in a piston/cylinder (Fig. P4.110) with a massless piston loaded with a linear spring and the outside atmosphere. Initially the spring force is zero and \(P_{1}=\) \(P_{0}=100 \mathrm{kPa}\) with a volume of \(0.2 \mathrm{m}^{3} .\) If the piston just hits the upper stops, the volume is \(0.8 \mathrm{m}^{3}\) and \(T=600^{\circ} \mathrm{C} .\) Heat is now added until the pressure reaches 1.2 MPa. Find the final temperafure, show the \(P-V\) diagram and find the work done during the process.

Helium gas expands from 20 psia, 600 R, and 9 \(\mathrm{ft}^{3}\) to 15 psia in a polytropic process with \(n=\) 1.667. How much work does it give out?

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.