Peoples Physics Book Version-2

20.1. Thermodynamics http://www.ck12.org

V=T

R

P 0

R,P 0 constants

In standard conditions on earth,P 0 ≈ 100 ,000Pa, so

V=T×R× 10 −^5

Equivalently, any two temperature-volume pairs can be related by the formula (why?):

T 2 =T 1

V 2

V 1

.

Such a setup might look like this:

FIGURE 20.6

What an ideal gas thermometer setup might look like

Therefore, a Kelvin scale ideal gas thermometer would function according to the following principle: bring the
balloon into thermal contact with a substance, wait for it to reach thermal equilibrium, measure its volume, and
convert that into temperature.

Alternatively, by finding the volume of the balloon at a temperature that corresponds to some easily observable
physical event (the melting point of water, for instance) we can nowfind any other temperatureby multiplying the
original (in Kelvins) by the ratio of the volumes.

We can illustrate how one might use the relationship between volume and temperature for a Kelvin scale ideal
thermometer in the following manner: