21 - 25 Physics SBAs for the Primary FRCA

21 - 25 Physics SBAs for the Primary FRCA
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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


  • 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.