What is the difference between the combination magnet-magnet and magnet-iron?
Magnets and iron attract each other but are not able to repel each other.
At full contact, the attraction between magnet and iron is the same as the attraction between two equal magnets.
As the distance increases, however, the attraction between magnet and iron becomes distinctly weaker than the attraction between two magnets.
This is due to the iron's low remanence.
Table of Contents
Difference regarding repulsion
A permanent magnet and in iron plate attract each other, but there is no repulsion, like you can find between two permanent magnets (see FAQ regarding attraction and repulsion).
Difference regarding attraction
At full contact, the attractive force between a raw magnet and an iron plate is the same as the attractive force between two raw magnets.
However, with increasing distance, the attraction diminishes faster than the attraction between two raw magnets (see graph).
This statement can also be verified with our Adhesive Force Tool.
Please note: These facts apply to raw magnets.
For pot magnets the attractive force to iron is stronger than it is to another raw magnet (see FAQ about pot magnets).
Example using disc magnet S-12-06-N
x-axis: distance
y-axis: adhesive force
y-axis: adhesive force
pink: attraction magnet-magnet
blue: attraction magnet-iron
blue: attraction magnet-iron
Explaining the phenomenon
left: ferromagnetic material
right: molecular magnet
right: molecular magnet
Ferromagnetic material (iron, cobalt, nickel) contains microscopically small permanent magnets (molecular magnets).
These molecular magnets rotate individually and can be adjusted by external magnetic fields.
The material is thereby magnetised.
left: permanent magnet
right: ferromagnetic material
right: ferromagnetic material
Explaining remanence
Also a super magnet contains molecular magnets. During the production of a permanent magnet, they are adjusted by a very high field that is produced by electromagnets. After turning off this external magnetic field, the alignment in the permanent magnet stays more or less intact (remanence: remanere = remain). A permanent magnet can now, in turn, adjust and thereby magnetise the molecular magnets in other ferromagnetic material. That's what happens at full contact between magnet and iron: The magnet transfers its magnetisation to the iron and the iron acts like a magnet.Difference regarding remanence
The alignment of the molecular magnets does not stay permanent in every ferromagnetic material. After removing the external magnetic field, a lot, a little or practically no magnetisation may remain, depending on the internal features of the material.In a piece of high-purity iron, for instance, the order of molecular magnets disintegrates completely after removing the external field.
In a normal iron plate the alignment stays intact a little better, but it is still a lot less than in a super magnet.