Nov 30, 2022 2
Domains and Disks
Painting with magnets
by Shireen Adenwalla, Xiaoshan Xu
From the largest stars to the smallest atoms, magnetic fields surround us. Our Earth acts as a huge bar magnet, pulling compass needles to line up with the poles. The tiny magnetic bits in our phones and laptops, and in the large data centers we call “the cloud,” enable us to watch movies, listen to endless streams of music, play video games, and work from anywhere.
But magnetism can be beautiful as well as useful! While magnetic fields are invisible, they can be felt by other magnets, and the development of magnetic paint, magnetic nail polish, and magnetic field viewing papers allows us to see, write, and erase magnetic patterns as they respond to magnetic fields.
More specifically, magnetic materials tend to form patterns called domains, which are regions within the material where the direction of the atoms’ magnetism is aligned. The featured image shows a variety of magnetic domains over an area roughly equal to the cross section of a human hair, but you can also create domain patterns that are visible to the naked eye! All it takes is magnetic nail polish, a few magnets, and a steady hand!
Magnetars are a type of neutron star that produce external magnetic fields a billion times stronger than the most powerful magnets on Earth (source).
Grade levels: 6th grade - 8th grade
Approx time: 30 minutes
Things you'll need:
Magnetic nail gel (we used this Cat Eye Gel, but there are many varieties available)
Paper, aluminum foil and/or a stiff sheet of plastic
Q-tips for clean up and painting
A magnifying lens to see the magnetic domain patterns (optional)
(i) Magnets can be found at the sites above, or simply grab one from your fridge!
(ii) Lay the plastic sheet, aluminum foil or paper down on a hard, flat surface. We found stiff plastic works best.
(ii) Make sure you have a bright light illuminating the sheet.
(iii) Line up the nail polish bottles and the magnets so that they are within reach. You don't want the nail polish to dry while you are working with the magnets.
(i) Using the applicator in the nail polish bottle or a cotton swab, paint a few separate blobs on the sheet. You can try different colors or stick to just one color.
(ii) Use a refrigerator magnet to create a striped pattern in the nail polish. If you have a steady hand, you can hold the magnet above the nail polish, close to but not touching the surface, or you can slide the magnet underneath the plastic, paper, or aluminum sheet. Observe how certain regions get lighter, and how these regions change and rearrange themselves as the magnet moves. For the strongest effect, the magnet should be close to—but not touching!— the nail polish.
Here we used various magnets—including a regular refrigerator magnet, a rectangular magnet with two opposing domains, and a disc shaped magnet—to generate different patterns.
The closer your magnet is to the nail polish, the stronger the magnetic field and the more apparent the pattern will be.
What other patterns can you create? Why do you think these patterns arise?
We've attached an image of the field you'd expect from two bar magnets. Can you use other combinations of magnets to create new patterns? Try to figure out how the interaction of magnetic fields creates the shapes you see.
Why it Works
Magnetic nail polish has tiny, black iron particles embedded in the liquid. If there are no magnetic fields around, the particles are evenly distributed in the liquid. When a magnetic field is applied, however, the iron is magnetized, generating a visual pattern as the iron particles concentrate in areas where the magnetic field is strongest. Magnets of different shapes have different patterns of magnetic fields that dictate how the iron particles will move.
To see how scientists are taking the concept of magnetic liquids to the next level, check out the post Ferromagnetic Liquids Take Shape!
A bar magnet is dropped into a cavity within a container. The container is filled with iron filings that are suspended in fluid. The filings are pulled in by the magnet, showing the 3D magnetic field lines. (source)
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