Magnetic Force that Makes a Solenoid Valve Work

In summary, the magnetic force associated with moving charged particles (Lorentz Force) is different from the regular force exerted by a magnetic field on a magnet or ferromagnetic material. The magnetic energy density in a field = ½ * B * H [ J/m3 ], and the pulling force can be calculated from: F = -dE/ds.
  • #1
AvroArrow
210
0
Hi guys,
I am having quite the struggle finding a good resource to explain the difference between the magnetic force associated with moving charged particles (Lorentz Force) and just the regular force exerted by a magnetic field on a magnet or ferromagnetic material. I am trying to apply this to the solenoid valve, which is essentially just an electromagnet that creates a magnetic field which moves a plunger.

In this video:


the gentleman says at around the 0:08 mark that the magnetic field pulls the plunger, I am curious as to what force is pulling this plunger. It is not the Lorentz force because there are no charged particles moving in the plunger, so what other type of magnetic force is at play here?

Any sort of clarification or resources would be very appreciated,
Thanks.
 
Engineering news on Phys.org
  • #2
AvroArrow said:
I am curious as to what force is pulling this plunger.
A magnetic field concists of two different fields:

- A magnetic field strength ( H-field ) with unit: A/m
- A magnetic induction ( B-field ) with unit: Tesla

. . just like electricity consists of voltage and current.

The magnetic energy density in a field = ½ * B * H [ J/m3 ]
At the end of the rod, connected to the valve, the B-field will be the same at each side of the surface, but the H-field will not because the permeabilty in air/iron is different:

In air: B = μ0*H
In iron: B = μ0r*H

So if μr as for iron = 900 ( typical value ), the H-field will become 900 times stronger in air than in iron, and so will will the magnetic energy density.

Now, mother nature hates high magnetic energy density, and wants somehow to get rid of it. So if that high density in a volume of air just outside the rod could be substituted by iron, mother nature will be happy, and will pull iron into the volume of air.

The pulling force can be calculated from:

F = -dE/ds , E = total magnetic energy in the system, s = length that the rod is moved.
 
  • Like
Likes AvroArrow
  • #4
Jony130 said:

Thanks, awesome link,really cleared things up for me. I am always amazed by the incredible "google search game" you guys have. I have no idea how you guys find these helpful links while all I can find is complicated PhD thesis papers that are always way beyond me. Is there another secret internet I am not aware of? ha ha thanks again.

Cheers,
 
  • #5
Hesch said:
A magnetic field concists of two different fields:

- A magnetic field strength ( H-field ) with unit: A/m
- A magnetic induction ( B-field ) with unit: Tesla

. . just like electricity consists of voltage and current.

The magnetic energy density in a field = ½ * B * H [ J/m3 ]
At the end of the rod, connected to the valve, the B-field will be the same at each side of the surface, but the H-field will not because the permeabilty in air/iron is different:

In air: B = μ0*H
In iron: B = μ0r*H

So if μr as for iron = 900 ( typical value ), the H-field will become 900 times stronger in air than in iron, and so will will the magnetic energy density.

Now, mother nature hates high magnetic energy density, and wants somehow to get rid of it. So if that high density in a volume of air just outside the rod could be substituted by iron, mother nature will be happy, and will pull iron into the volume of air.

The pulling force can be calculated from:

F = -dE/ds , E = total magnetic energy in the system, s = length that the rod is moved.

Thanks, I think I am slowly figuring it out. I never put the pieces of magnetic flux and magnetic field strength together until now. This pull force of the magnet seems to completely independent of this Lorentz Force I have studied in school. My understanding of this pull force is it is the result of the gradient between magnetic energy density which results from the difference in permeability of the air and the ferromagnetic material. The flux lines don't care about the difference in permeability, (is that why the B field is the same on each side of the surface? ) but the magnetic field strength does care about the permeability difference which is why there is a gradient, which is why the force is generated.

Cheers,
 

What is a solenoid valve?

A solenoid valve is an electromechanical device that controls the flow of a fluid or gas by using a magnetic field to move a plunger or piston inside the valve. It is commonly used in various industrial and commercial applications to regulate the flow of liquids or gases.

How does a solenoid valve work?

A solenoid valve works by using a solenoid, which is a coil of wire, to generate a magnetic field when an electric current passes through it. This magnetic field attracts a plunger or piston inside the valve, which opens or closes the valve to control the flow of fluid or gas through it.

What is the role of magnetic force in a solenoid valve?

Magnetic force is the driving force behind the operation of a solenoid valve. When an electric current flows through the solenoid, it creates a magnetic field that interacts with the plunger or piston, causing it to move and open or close the valve. This allows for precise and efficient control of the flow of fluid or gas through the valve.

What are the advantages of using a solenoid valve?

Solenoid valves have several advantages, including fast response times, high reliability, and the ability to be remotely controlled. They also have a simple design and are relatively easy to install and maintain. Additionally, solenoid valves can handle a wide range of temperatures and pressures, making them suitable for a variety of applications.

What are some common applications of solenoid valves?

Solenoid valves are commonly used in industrial and commercial settings, such as in water treatment systems, HVAC systems, refrigeration units, and irrigation systems. They are also used in household appliances, such as washing machines and dishwashers, as well as in automotive and medical equipment.

Similar threads

  • Electrical Engineering
Replies
7
Views
777
  • Electrical Engineering
Replies
4
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
244
  • Electrical Engineering
Replies
9
Views
4K
  • Electromagnetism
Replies
2
Views
799
Replies
8
Views
952
  • Introductory Physics Homework Help
Replies
4
Views
269
  • Electrical Engineering
Replies
28
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
263
Replies
1
Views
1K
Back
Top