21 - 25 Physics SBAs for the Primary FRCA
Question 21
You have boldly suggested Gay-Lussac's gas law as an answer to a completely unrelated question, and your consultant has decided to explore your understanding of said law.
Which of the following is not true of Gay-Lussac's law?
- Pressure is proportional to temperature at constant volume
- It is based on the kinetic molecular behaviour of gases
- It uses temperature in Celsius
- It is the gas law of relevance in a Bourdon gauge
- It is why compressed gas cylinders have a storage temperature limit
Answer
- It uses temperature in Celsius
You have to use Kelvin, otherwise you get all sorts of strange numbers, especially at negative celsius temperatures.
All of the others are true.
A Bourdon gauge has a set volume of gas inside a coiled tube, and as temperature increases, the pressure of the gas in the tube increases, uncoiling the tube and twisting the dial displaying the temperature.
Unsurprisingly, if you heat a compressed gas cylinder up it will probably explode.