Understanding the physics behind a Solenoid Valve

[jackmrrabbit]

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.

 

[kuruman]

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.

 

[jackmrrabbit]

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!

 

[Lnewqban]

If you place a piece of steel next to the top of the solenoid while energized, you will feel a strong magnetic force.