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Iron filings in the water

Visualising magnetic field lines in 3D
Author: Mirko Pafundi, Asti, Italy
Online since: 08/11/2016, Number of visits: 541248
This experiment visualises magnetic field lines in 3D.
We have all played with iron filings in our youth and made them move over the table. That gives you an idea of the shape of a magnetic field. If you put iron filings into a fluid, however, you can see the shape of the magnetic field even better. Why? The fluid slows down the iron filings, which helps observe the magnetic field lines much better.

Make your own iron filings

For this experiment you need very fine iron filings, otherwise they sink to the bottom of the bottle too fast. That's why I've made my own iron filings from an iron rod and a milling cutter.
Then I sifted the iron filings with a very fine kitchen strainer to get rid of larger pieces.

Clean iron filings

Finally, I put the iron filings into water to clean them. It is easy to separate the iron filings from dirt: Just shake the glass and place a magnet to the bottom side. The dirt stays in the water and can easily be removed. The iron filings stay on the glass bottom. I recommend at least 10 repetitions.


Now we need a bottle that should be transparent, tall and narrow.
Fill the bottle with water, put the cleaned iron filings into it and seal the bottle.
If you have a nice collection of neodymium magnets, now is the time to take them out to observe the form of their magnetic fields. In my case it's small block magnets, two large ferrite magnets and a ring magnet (connected below).

Other options

If you wanted to slow down the movement of the iron filings even more, you could replace water with oil. I heard silicone oil is the best (transparent and dense). Oil has the additional benefit that iron filings don't oxidise.
Note from the supermagnete team:
Using oil is very similar to our product ferrofluid. We published several applications on that.
You can also use our iron filings instead of making your own, but they may really sink too fast.

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