# How did Charles obtain his law when absolute temperature wasn't define

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• ovais
In summary: In 1780, Charles calculated that the absolute temperature could be defined using the equation PV=nRT, where P is pressure, V is volume, and T is the absolute temperature. This was later refined by Lord Kelvin in 1848, who showed that the absolute temperature could be defined as the lowest temperature at which a pressure-volume curve crosses the zero line.
ovais
TL;DR Summary
The Kelvin temperature (T) was not introduced during the time of Charles, so there was no definition of absolute temperature T during that time how then Charles Proposed that at constant pressure Volume (V);of gas is directly proportional to it's absolute temperature T( V/T= constant) ?
Hi all

These days I am refreshing my knowledge on the concept and measurement of temperature. One way of defining temperature is in terms of how it is measured. This can be done by observing the variation of some properties which vary linearly with the hotness(temperature) of bodies. I studied about Celsius scale, Fahrenheit scale no problem. But when I come to study absolute scale few questions and doubts arises in my mind.

One of doubts is that Charles brought his law in 1780 and the absolute temperature scale by Lord Kelvin came is 1848 right? Now in introduction to Kelvin scale they are referring Charles Law and Boyles Law and use PV=nRT, to arrive at the fact that their is some minimum possible temperature and if we extrapolate the(pressure temperature) P -T graph graph then that minimum temperature is -273.15°C. Which is known to be Zero Kelvin.

This doesn't make sense to me because without Kelvin Scale we should not talk about Charles law at the first place. I must missing something. Any help will be highly appreciated!

Thanks a bunch:)

Last edited:
This series of videos explores the history of thermodynamics theory. Perhaps one of them may have the answer you seek. I put the playlist link in code tags to prevent the PF software from converting it to a link to a single video.

Html:
https://www.youtube.com/playlist?list=PLepnjl2hm9tHRMTdVyJ8t9HB6TZ63hFdU

vanhees71
anorlunda said:
This series of videos explores the history of thermodynamics theory. Perhaps one of them may have the answer you seek. I put the playlist link in code tags to prevent the PF software from converting it to a link to a single video.

Html:
https://www.youtube.com/playlist?list=PLepnjl2hm9tHRMTdVyJ8t9HB6TZ63hFdU
Video topics look relevant. Start watching them. Will respond after watching.

Thanks anorlunda

vanhees71

## 1. How did Charles obtain his law?

Charles' law was obtained through experimentation and observation of the relationship between the volume and temperature of a gas at a constant pressure.

## 2. Why was absolute temperature not defined when Charles obtained his law?

At the time when Charles obtained his law, the concept of absolute temperature had not yet been developed. It was not until later that scientists, such as Lord Kelvin, defined the concept of absolute temperature and its scale.

## 3. What is the relationship between Charles' law and absolute temperature?

Charles' law states that at a constant pressure, the volume of a gas is directly proportional to its temperature. This means that as temperature increases, volume also increases. This relationship is also reflected in the absolute temperature scale, where the temperature increases as the volume of a gas increases.

## 4. How is Charles' law used in modern science?

Charles' law is a fundamental principle in the study of thermodynamics and is used in various fields of science, including chemistry, physics, and engineering. It is used to predict the behavior of gases and is also an important concept in the ideal gas law.

## 5. Can Charles' law be applied to all gases?

Charles' law can be applied to most gases at low pressures and temperatures. However, at high pressures and low temperatures, the behavior of gases may deviate from what is predicted by the law. This is due to the fact that gases may become more complex and behave more like liquids or solids under these conditions.

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