# Analyzing the Force of Two Disk Magnets on a Metal Plate

• Kupa140
In summary, the conversation discusses a situation with two disk magnets and a metal plate fixed between them. The magnets have the same poles facing each other, creating a plane of symmetry where there is no magnetic field. The question is posed about the effect of rotating the metal plate between the magnets and whether the magnetic forces would cancel each other out or not. The conclusion is that there is no field halfway between the magnets, making it impossible for the metal plate to rotate between them.
Kupa140
The situation is as follows. We have two disk magnets. One is fixed on the ground, table, or surface and has the north pole facing up. Then we have a metal plate fixed on the vertical axis rod or something similar such that it can't move up or down, but only rotate horizontally with as less friction as possible. The metal piece is slightly above the surface of the first magnet and the magnet will obviously attract it.

We also have right above the first magnet and the needed space for the metal piece a fixed cylindrical tube holding the second identical magnet inside it, and it also allows the second magnet to slide up and down within the tube. The magnets are facing each other with the same poles, so north north. With nothing between the magnets, the second one would float above the first magnet with a given distance calculated by their repulsive force and so on.

Now to the question, the metal piece now rotates such that it's between the two magnets and the magnetic filed lines will now pass through the metal instead of air, the second one will fall lower than it's previous position and both will be attracted to the metal, would their force on the metal cancel each other out? If not, is their pull on the metal greater or lower than the necessary force needed to rotate the metal piece out of the position between them? My assumption is that a great deal is perpendicular on the metal and since the metal piece is fixed it should be less.

Last edited by a moderator:
Welcome to PF.

Kupa140 said:
The magnets are facing each other with the same poles, so north north.
There will be a plane of symmetry between the two north poles where there is no field. The two magnetic fields do not connect and flow through the two magnets, they bend out sideways and so avoid each other.

Kupa140 said:
Now to the question, the metal piece now rotates such that it's between the two magnets and the magnetic filed lines will now pass through the metal instead of air, ...
There is no field halfway between the magnets where you place the metal plate.

Kupa140
Baluncore said:
Welcome to PF.There will be a plane of symmetry between the two north poles where there is no field. The two magnetic fields do not connect and flow through the two magnets, they bend out sideways and so avoid each other.There is no field halfway between the magnets where you place the metal plate.
It took me a while but now i understand, thank you.

hutchphd and berkeman

• Electrical Engineering
Replies
1
Views
2K
• Other Physics Topics
Replies
17
Views
3K
• Electrical Engineering
Replies
9
Views
11K
• General Engineering
Replies
3
Views
448
• Classical Physics
Replies
7
Views
949
• Electromagnetism
Replies
1
Views
911
• Electrical Engineering
Replies
1
Views
1K
• Introductory Physics Homework Help
Replies
1
Views
422
• Electromagnetism
Replies
7
Views
436
• Introductory Physics Homework Help
Replies
2
Views
378