# A question about magnetic field lines

In the simple experiment of spraying iron filings around a magnet, why doesn't the magnetic field (provided that it is strong enough) cause the iron filings to form a $$3\mathrm D$$ skeleton along the magnetic field lines?

I suggest if we replaced iron filings with a less dense ferromagnetic material or even with iron nanoparticles , then the required skeleton can be formed. But I don't know if there was any previous experiment done on this hypothesis.

• @user3518839 I said provided that the magnetic field is strong Commented Jan 31, 2020 at 11:41

Fill a bottle with mineral oil and a couple of table spoons of iron filings.

Seal the bottle and shake it up.

In effect the mineral oil "dilutes" the effect of gravity.

In air there is a 3D representation of the magnetic field but the gravitational forces win in the end.

I have not found any references to astronauts doing this experiment whilst orbiting the Earth.

• @Fracher I meant in air and I edited the question Commented Jan 31, 2020 at 13:50
• What if the used material was of density closer to that of air Commented Jan 31, 2020 at 20:23

I think it is possible but that would require a really strong magnet and the magnet would have to be arranged in this manner. The iron filings will have to form a loop and support themselves in mid-air. This is because the filings adjacent to each filing are acting as tiny ferromagnetic materials and holding them up.

For some reason I think the horizontal magnet setup ($$1$$st image) may not work as that would require an even stronger magnetic field because that way the direction of field lines on the sides of the magnets will be nearly perpendicular to the direction of the weight of the filings.

This will strain the setup and as a result the arrangement will be very prone to instability.

One more thing should be noted that simply increasing the strength of the magnet will help us so long as the iron filings don't reach saturation magnetization. After that increasing the strength of the magnet will have little to no effect.

• I edited the question Commented Jan 31, 2020 at 13:56