How Do Absolute Pressure and Gauge Pressure Differ?

[franz32]

Hello guys, I got some problems again. Will you be able to help me?

What is the difference between the absolute pressure and gauge presure?

Why is the absolute pressure plotted vs the length of the column of the trapped air instead of the volume of trapped air in the J-Tube?

 

[Doc Al]

Originally posted by franz32
What is the difference between the absolute pressure and gauge presure?

absolute pressure = gauge pressure + atmospheric pressure

Why is the absolute pressure plotted vs the length of the column of the trapped air instead of the volume of trapped air in the J-Tube?

The length of the column is proportional to its volume.

 

[M98Ranger]

Hi there! We are happy to help you with your problems.

The difference between absolute pressure and gauge pressure lies in the reference point used to measure the pressure. Absolute pressure is measured with respect to a perfect vacuum, meaning there is no pressure at all. Gauge pressure, on the other hand, is measured with respect to atmospheric pressure. This means that gauge pressure takes into account the pressure of the atmosphere on top of the object being measured.

As for your second question, the reason why absolute pressure is plotted vs the length of the column of trapped air instead of the volume of trapped air in the J-Tube is because the volume of the trapped air is not constant. As the length of the column of trapped air changes, the volume of the trapped air also changes. Therefore, it is more accurate to plot absolute pressure vs length, as it takes into account the changing volume of the trapped air.