Understanding the physics behind a Solenoid Valve

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    Physics Solenoid Valve
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Discussion Overview

The discussion focuses on the physics of solenoid valves, particularly the mechanisms by which they operate when energized and the role of magnetic forces and spring forces in their function. The scope includes conceptual understanding and technical explanations related to electromagnetism and mechanical interactions.

Discussion Character

  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants argue that the operation of a solenoid valve is not related to induction but rather depends on whether the solenoid is energized, with the current creating a magnetic field that pulls the plunger against a spring force.
  • It is noted that for the solenoid to effectively pull the plunger, the magnetic force must exceed the downward spring force.
  • One participant mentions that if the plunger is a permanent magnet, the current in the solenoid must create an attractive force between the solenoid and the plunger.
  • A later reply suggests that placing a piece of steel near the energized solenoid will result in a strong magnetic force, indicating the presence of magnetic fields in operation.

Areas of Agreement / Disagreement

Participants generally agree on the basic principles of how a solenoid valve operates, but there are nuances in the details regarding the role of induction and the nature of the magnetic forces involved. The discussion remains somewhat unresolved regarding the implications of using permanent magnets in the system.

Contextual Notes

There are assumptions about the characteristics of the materials involved (e.g., the nature of the plunger) and the specific conditions under which the solenoid operates that are not fully explored. The discussion does not clarify the definitions of terms like "induction" in this context.

jackmrrabbit
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TL;DR
In the scenario where a permanent magnetic is placed inside a solenoid (like a solenoid valve) I am confused regarding the physics of how the EMF generated by running current through the solenoid keeps the permanent magnetic elevated (open in a normally closed solenoid valve) over time.

Doesn’t induction only occur due to a changing magnetic field? If the permanent magnetic reaches its max displacement, why is there still a force keeping it elevated? Any help would be much appreciated.
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I don't believe this has anything to do with induction. It has to do with whether the solenoid is energized or not. The current in the solenoid turns it into a magnet and the plunger, made from some kind of magnetic material, will be pulled in against the downward spring force to minimize the magnetic potential energy. Of course, for this to work, the spring force must be weaker than the magnetic force. When the current to the solenoid is cut, the magnetic force disappears and the spring pushes the plunger back down.

On edit:
If the plunger is a permanent magnet, the current in the solenoid must be such that the force between the solenoid-magnet and plunger-magnet is attractive.
 
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kuruman said:
I don't believe this has anything to do with induction. It has to do with whether the solenoid is energized or not. The current in the solenoid turns it into a magnet and the plunger, made from some kind of magnetic material, will be pulled in against the downward spring force to minimize the magnetic potential energy. Of course, for this to work, the spring force must be weaker than the magnetic force. When the current to the solenoid is cut, the magnetic force disappears and the spring pushes the plunger back down.

On edit:
If the plunger is a permanent magnet, the current in the solenoid must be such that the force between the solenoid-magnet and plunger-magnet is attractive.
That makes a lot more sense. Thank you!
 
If you place a piece of steel next to the top of the solenoid while energized, you will feel a strong magnetic force.
 

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