Why Are Isothermal Process Assumptions Necessary in Thermodynamics?

[trojanviking]

In my textbook (Physics Principles With Applications - Giancoli 7th Edition) it states that

"We assume the gas is in contact with a heat reservoir (a body whose mass is so large that, ideally, its temperature does not change significantly when heat is exchanged with our system). We also assume that a process of compression or expansion is done very slowly, so that the process can be considered a series of equilibrium states all at the same constant temperature."

I am trying to wrap my head around why these assumptions were made.

Thanks!

 

[Malverin]

In my textbook (Physics Principles With Applications - Giancoli 7th Edition) it states that

"We assume the gas is in contact with a heat reservoir (a body whose mass is so large that, ideally, its temperature does not change significantly when heat is exchanged with our system). We also assume that a process of compression or expansion is done very slowly, so that the process can be considered a series of equilibrium states all at the same constant temperature."

I am trying to wrap my head around why these assumptions were made.

Thanks!

Pressure, volume and temperature are dependant on each other

When volume expands, pressure will drop and to keep the temperature constant, you have to get heat from the enviroment(cooling it).
Heat transfer needs time, so to have minimum temperature fluctuations is better to expand the volume slowly .

By compression, volume gets smaller and pressure rises.
To keep the temperature constant, you have to transfer heat to the environment (heating it)

 

[Andrew Mason]

In my textbook (Physics Principles With Applications - Giancoli 7th Edition) it states that

"We assume the gas is in contact with a heat reservoir (a body whose mass is so large that, ideally, its temperature does not change significantly when heat is exchanged with our system). We also assume that a process of compression or expansion is done very slowly, so that the process can be considered a series of equilibrium states all at the same constant temperature."

I am trying to wrap my head around why these assumptions were made.

I expect that the author wants to describe a reversible isothermal process.

AM

 

[wreckemtech]

In my textbook (Physics Principles With Applications - Giancoli 7th Edition) it states that

"We assume the gas is in contact with a heat reservoir (a body whose mass is so large that, ideally, its temperature does not change significantly when heat is exchanged with our system). We also assume that a process of compression or expansion is done very slowly, so that the process can be considered a series of equilibrium states all at the same constant temperature."

I am trying to wrap my head around why these assumptions were made.

Thanks!

Unless those assumptions are made, there is no way to do basic analysis for ideal systems. And doing in-depth analysis of thermodynamic systems would require higher levels of proficiency in both mathematics and physics than someone taking an introductory thermo class would be expected to have going into it. And it's good to know what an ideal systems behave in terms of analyzing efficiency of real ones.

We all learn to crawl before walking. And from there it still takes a lot of training and dedication to run a marathon.

 

[sardar]

The assumptions mentioned in your textbook are made in order to simplify the analysis of thermodynamic processes involving gases. By assuming that the gas is in contact with a heat reservoir, we can ensure that the temperature of the gas remains constant during the process. This allows us to use the ideal gas law and other thermodynamic equations, which are only valid for isothermal processes.

Additionally, by assuming that the process is done slowly, we can also assume that the gas is always in thermal equilibrium with its surroundings. This means that the gas will have enough time to adjust to any changes in pressure or volume, and the temperature will remain constant throughout the process. This simplifies the analysis and allows us to use equations that are only valid for equilibrium states.

Overall, these assumptions are necessary in order to use the ideal gas law and other thermodynamic equations to analyze the behavior of gases in isothermal processes. Without these assumptions, the analysis would be much more complex and difficult to understand.