# The force and torque between two permanent magnets?

• flofelis
In summary: It's easier to measure acceleration or displacement (due to the laws of motion). I don't know what equipment you could use to measure torque.
flofelis
Hi all =)

I am interested to find the forces and torques between two (diametrically magnetized) cylindrical permanent magnets (PMs) placed within a vicinity, as shown below:

The NdFeB PMs placed beside one another with a distance, d. Both are rotated by independent external sources (I have solenoids to independently drive the PMs). This will affect each PM in terms of the torque and force.

So I am just wondering if I could use the same force/torque equations (e.g. for the force as shown below) between two axially magnetized PMs for the diametrically magnetized ones as well:

I do not have a software for this, thus I would need to model it mathematically.. (i have spent weeks trying to find a way to do it but I ran out of idea)

I see that most cases are calculated for axially magnetized PMs so I am not sure if the generally available equations for the axially magnetized PMs can be used in my case. I got pretty confused as to how I should compute the dynamics (force and torque of one PM (primary) when another is closely present).. as well as how far should the PMs be apart so I could ignore the effect of the other PM onto the primary PM.

Looking forward to hearing from anyone with ideas and advice =) Thank you very much!

Dr. Courtney said:
Thanks, Dr Courtney. Seems like FEM is the best way to approach problems like this?

Experiment is the best way. FEM can be tricky, and results must be validated to be reliable.

I have some hall effect sensors which could help get the magnetic field at a certain location..I could use that for force or torque verification through my equations. Do you have any suggestions on what sensors or equipment I could use in experiments as such? Thanks again~! =)

If your FEM or equation predicts force, you should measure force. The same is true with torque. There are a lot of ways to measure force: displacements of pendula, electronic sensors, etc. Measuring torque is harder.

## 1. What is the force between two permanent magnets?

The force between two permanent magnets is a result of their magnetic fields interacting with each other. When two magnets are placed close together, their magnetic fields either attract or repel each other, depending on the orientation of their poles.

## 2. How is the force between two permanent magnets calculated?

The force between two permanent magnets can be calculated using the formula F = (μm * μM * A) / (2 * d^2), where μm and μM are the magnetic permeabilities of the two magnets, A is the area of the magnets, and d is the distance between them.

## 3. What is torque in relation to two permanent magnets?

Torque is the measure of the twisting force between two magnets. This occurs when the magnets are not aligned perfectly and there is a rotational force between them.

## 4. How is torque between two permanent magnets calculated?

The torque between two permanent magnets can be calculated using the formula τ = μm * μM * V * sin(θ), where μm and μM are the magnetic permeabilities of the two magnets, V is the volume of the magnets, and θ is the angle between the two magnets' magnetic fields.

## 5. How does the distance between two permanent magnets affect the force and torque?

The force between two permanent magnets decreases as the distance between them increases. Similarly, the torque between two permanent magnets also decreases as the distance between them increases. This is because the strength of the magnetic field decreases with distance, resulting in a weaker force and torque between the magnets.

• Electromagnetism
Replies
3
Views
1K
• Electromagnetism
Replies
3
Views
382
• Electromagnetism
Replies
5
Views
1K
• Electromagnetism
Replies
7
Views
577
• Electromagnetism
Replies
2
Views
833
• Electromagnetism
Replies
7
Views
1K
• Electromagnetism
Replies
5
Views
3K
• Electromagnetism
Replies
8
Views
2K
• Electromagnetism
Replies
6
Views
3K
• Electromagnetism
Replies
6
Views
3K