# Understanding the Repelling Forces of Magnets

• Stoney
In summary, the force between two magnets is proportional to the cross section area of the airgap between them and the energy in the airgap determines the force. Therefore, if a smaller magnet is used in place of a larger one, it will still experience the same amount of force as long as the distance and magnetic field remain constant. The force between two magnets also follows Newton's third law of action and reaction.
Stoney
Hi
Just wanted to know,

If I have two magnets of the same size with a pull force of say 30kg and use them to repel each other, the top magnet at a position close to the surface of the bottom magnet would be able to support around 30kg (I know repel force is not measured in kg). If I then replace the top magnet with a smaller one will it still be able to support around 30kg at the same position as it is still being repelled from the bottom one with around 30kg of force?

Thanks
Stoney

Stoney said:
If I then replace the top magnet with a smaller one will it still be able to support around 30kg at the same position as it is still being repelled from the bottom one with around 30kg of force?
What do you mean by "smaller one"?
The force is proportional to the cross section area of the airgap between the magnets, if the B-field, H-field and distance are kept constant.

Hesch said:
What do you mean by "smaller one"?
The force is proportional to the cross section area of the airgap between the magnets, if the B-field, H-field and distance are kept constant.

Sorry, say the bottom magnet is 50mm x 25mm x 10mm with a force of 30kg and the smaller top magnet is 50mm x 25mm x 3mm with a force of 9kg, would this top magnet still be able to support around 30kg as it is being repelled by 30kg of force from the bottom magnet. I hope I have explained myself properly. Thanks for your help.

Stoney said:
Sorry, say the bottom magnet is 50mm x 25mm x 10mm with a force of 30kg and the smaller top magnet is 50mm x 25mm x 3mm with a force of 9kg, would this top magnet still be able to support around 30kg as it is being repelled by 30kg of force from the bottom magnet.
The magnet itself has no "force". It's the magnetic energy in the airgap that produces force.
The magnetic energy density in the airgap = ½*B*H [ J/m3 ]. If you close up the magnets this energy density will be increased due to changes in the H-field and the B-field. So somebody must add this energy to the airgap, and this is done by using force to close up the magnets.
Energy = force * distance.

That's why magnets are attracting/repelling each other. It has nothing with "north" and "south-poles" inside the magnets to do. They don't exist.

Remember that two magnets will always attract each other with the same force ( not 9kp vs. 30kp ). Newton states that with his law: action = reaction.

The cross section area of the airgap, using two different magnets, must be regarded as the area of the smallets magnet, because this is the area that "limits" the airgap.

Last edited:
Stoney
Hesch said:
The magnet itself has no "force". It's the magnetic energy in the airgap that produces force.
The magnetic energy density in the airgap = ½*B*H [ J/m3 ]. If you close up the magnets this energy density will be increased due to changes in the H-field and the B-field. So somebody must add this energy to the airgap, and this is done by using force to close up the magnets.
Energy = force * distance.

That's why magnets are attracting/repelling each other. It has nothing with "north" and "south-poles" inside the magnets to do. They don't exist.

Remember that two magnets will always attract each other with the same force ( not 9kp vs. 30kp ). Newton states that with his law: action = reaction.

The cross section area of the airgap, using two different magnets, must be regarded as the area of the smallets magnet, because this is the area that "limits" the airgap.

Ok I think I understand now, thanks for your help.

## What are repel forces of magnets?

Repel forces of magnets refer to the force that causes two magnets with like poles to push away from each other.

## How do magnets repel each other?

Magnets repel each other when the like poles (north and north or south and south) are facing each other. This is due to the alignment of the magnetic fields.

## Can all magnets repel each other?

No, not all magnets can repel each other. Only magnets with opposite poles facing each other will attract, while magnets with like poles will repel.

## What factors affect the strength of repel forces between magnets?

The strength of repel forces between magnets is affected by the distance between the magnets, the strength of the magnets, and the alignment of their poles.

## How can we increase the repel force between magnets?

The repel force between magnets can be increased by using stronger magnets or by decreasing the distance between them. Additionally, aligning the poles of the magnets in the same direction can also increase the repel force.

Replies
1
Views
2K
Replies
3
Views
2K
Replies
14
Views
2K
Replies
11
Views
685
Replies
14
Views
2K
Replies
32
Views
2K
Replies
35
Views
4K
Replies
4
Views
1K
Replies
6
Views
5K
Replies
8
Views
987