General information on back pressure in a syringe

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SUMMARY

This discussion focuses on the concept of back pressure in syringes, particularly when comparing syringes filled with air versus those filled with water. The phenomenon occurs when the plunger is depressed and then released, causing the plunger to move back slightly due to the compressibility of air. The Boyle-Gay Lussac law is referenced to explain the relationship between pressure and volume in this context. Additionally, the concept of hysteresis is mentioned as a relevant factor in understanding the behavior of the syringe.

PREREQUISITES
  • Understanding of Boyle's Law and its application in fluid mechanics
  • Basic knowledge of compressible versus incompressible fluids
  • Familiarity with syringe mechanics and seal types
  • Introductory physics concepts related to pressure and volume
NEXT STEPS
  • Research the Boyle-Gay Lussac law and its implications in fluid dynamics
  • Study the properties of compressible fluids, specifically air, in various scenarios
  • Explore the concept of hysteresis in mechanical systems
  • Investigate different types of syringe seals and their impact on performance
USEFUL FOR

This discussion is beneficial for physics students, medical professionals using syringes, and engineers involved in fluid dynamics or mechanical design.

Petra de Ruyter
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Hi all

I'm looking for general information on "back pressure" specially in a syringe. So when you put your finger over the top of a syringe and depress the plunger then release the pressure on the plunger and the plunger moves back slightly. I'm struggling to find some specific information that will help me explain this scenario? So any reading that you think would be good please provide a link.

Cheers
 
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Hello Petra,

Did you notice a difference between syringes filled with air as opposed to syringes filled with water ?
 
This syringe is filled with air only and connected to another syringe that is empty. I'm looking for a text reading that will help me understand what is happening, I don't necessary need anything solved just need a good resource that I can refer to.
 
Air is compressible: when you increase the pressure (push down the syringe) the volume decreases. The air in the reduced volume presses back.
When all this is done at approximately the same temperature, the product of air volume (in the two syringes combined) and pressure is constant (Boyle-Gay Lussac law). Google or look it up in an introductory physics textbook.
 
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Also, Google "hysteresis." You haven't identified/specified seal type.
 
Many thanks to all that have posted.
 

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