# Isothermal Process Question

1. Dec 12, 2013

### 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!

2. Dec 12, 2013

### Malverin

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 enviroment (heating it)

Last edited: Dec 12, 2013
3. Dec 12, 2013

### Andrew Mason

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

AM

4. Dec 12, 2013

### wreckemtech

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 alot of training and dedication to run a marathon.