Magnetic attraction seen with ferrocell. The magnetic field pattern is the same as that for repulsion when viewed with iron filings. Why?

enter image description here

  • $\begingroup$ I recently contributed to a virtual Magnetics conference that explains what you are questioning. Here is a link to the movie- youtu.be/-I3HDrR9pts and here is a link to the references- ferrocell.us/references/Links%20to%20References%20mmm2021.pdf I hope my presentation makes the Ferrocell's response to magnetism and light more understandable. ~Timm Vanderelli, Ferrocell USA $\endgroup$
    – Timm
    Sep 9 at 14:07

I found this video that has both attractive and repulsive set ups on a ferrocell . They look different, and justify the commentator " field lines or something like them".

The lines you see are the fields interacting with the ferrocell, differently than the orientation of the dipoles, which are what the iron filings show.

My conclusion is that the ferrocell lines do not show the direct orientation of dipoles that iron filings do, lining up with the field lines, they are possibly a second level magnetic interaction in the cell.


This is how iron filings show repulsion


And this is how they show attraction lines.

The effects registered in the video must be some optical effect induced by the existence of nano size dipoles which are not visible, possibly difraction.

  • $\begingroup$ Ferrofluid in a ferrocell is just iron filings at a nano scale, tough. One explanation I saw is that the scale of iron filings makes them "one-directional", showing only half of the magnetic field, whereas nano-sized equivalent is bi-directional. This is showing ferrofluid under a microscope, and how the "iron filings" in it align with magnetic lines of force, youtube.com/watch?v=o0vFWo4BLM8 $\endgroup$
    – pehr
    May 18 '19 at 16:07
  • $\begingroup$ In the video you link the speaker at the end is talking of difraction. It is possible that the lines seen in your video, and in the one I linked, are optical difraction patterns from the intrinsic nano dipoles. a second level effect $\endgroup$
    – anna v
    May 18 '19 at 16:54
  • $\begingroup$ the field pattern for repulsion is the opposite as well from iron filings, i.imgur.com/kfdrjMn.jpg $\endgroup$
    – pehr
    May 18 '19 at 17:46
  • $\begingroup$ so it is not field lines that one sees in the cell, some sort of optical effect. $\endgroup$
    – anna v
    May 18 '19 at 18:01
  • $\begingroup$ if the premise that iron filings show field lines is correct, that premise could be false tough and the nano-size "iron filings" could be showing actual field, the other one favoured just because it has been around longer $\endgroup$
    – pehr
    May 18 '19 at 18:06

Pehr is correct. Iron filings are too low resolution to show all of the fine details of the field. The nanoparticles of nickel in the ferrofluid do a much better job at illustrating the point vector of magnetisation because they are simply smaller and shorter and are therefore exposed to more of a point vector of magnetism rather than a sum of point vectors.

A magnetically huge iron filing will orient according to the sum of that magnetic forces at that area in space it occupies which means it will aling in the typically expected fashion. At smaller scales, like with diluted ferrofluid, you can see better detail of the point vector at that location in space.

The lensing effect of the ferrofluid is therefore a more direct and accurate representation of the point vectors that make up the magnetic field.

Arguably, a ferrocell is the highest resolution representation of a magnetic field that we will ever be able to produce with ferromagnetic particles in a way that is observable to the naked eye.

Edit: also field lines are not the same. They're just huge. Look again in slow motion. You can see the field lines converge as the magnets are placed together and diverge on the repulsion side.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.