Why Does It Only Stick on One Side? The Magnetic Mystery of Magnet Sheets (Single-Sided Multipole Magnetization)
I’m Ken Kuwako, your Science Trainer. Every day is an experiment!
Have you ever noticed the advertising magnet sheets stuck to your refrigerator—those thin magnets from water-leak repair companies and other businesses? They may look like nothing more than simple promotional items, but hidden inside these thin sheets is a surprisingly clever magnetic structure. When I tried a simple experiment with the magnet sheets that often arrive in our mailboxes, my students were fascinated, shouting, “Why? Why does that happen?” Today, I’d like to show you the experiment and reveal the unexpected secret hidden inside these ordinary magnets.
Do you have a magnetic sheet stuck to your refrigerator? Maybe one of those promotional sheets from a “water-leak repair” company that was slipped into your mailbox. Take two of these sheets, place them on top of each other, and try pulling one of them sideways. You’ll feel a surprisingly funny, jerky resistance!
Why is the magnetic force only on one side?
I once visited the laboratory (which was also his home) of Professor Eiji Komori. While experimenting with some magnets bought at Daiso, we sprinkled iron filings over them and noticed something curious: only one side seemed to have magnetic force.
From a practical point of view, this design makes perfect sense—if the magnet only needs to stick on one side, why make both sides magnetic? But how exactly are the magnetic poles arranged inside the sheet? If we think about an ordinary magnet, it always has a north pole and a south pole, so you might expect magnetic field lines to emerge from both sides and allow either side to stick to metal. So we sprinkled iron filings over the surface, and something fascinating appeared!
Today, I’d like to introduce a simple experiment that lets you enjoy this fascinating pattern for yourself.
The Science Recipe
What you’ll need
An advertising magnet sheet from your mailbox (or one you buy yourself), iron filings, and a small container such as a film canister
How to do it
① Make several small holes in the lid of the container using an awl or similar tool. Then put the iron filings inside. Your “iron-filings shaker” is ready!
② Sprinkle the iron filings over the magnetic sheet and observe what happens.
③ Place two magnetic sheets together horizontally and pull one of them sideways. Try changing the direction and see how the resistance feels.
The results—and the secret behind the hidden stripes
When you sprinkle the iron filings over the sheet as in step ②, you’ll see a pattern like this.
That’s right—the filings form stripes. Pretty cool, isn’t it? If you try the other side, almost no iron filings stick because there is very little magnetic force there. So why does this striped pattern appear? My initial thought was that the north and south poles are arranged alternately in narrow strips, creating a structure that looks like a whole row of tiny U-shaped magnets lined up side by side. With this arrangement, the magnetic field is concentrated so that it emerges mainly from one side, which explains why the opposite side has very little magnetic force.
When you carry out experiment ③, you may notice that pulling the sheets in a particular direction produces a distinctive “clunk, clunk” sensation. This happens because the north and south poles alternate along the striped pattern, so areas where the two sheets attract and areas where they repel switch back and forth as you pull them. We also found that the sensation—the stripe width and the strength of the resistance—varies from one magnetic sheet to another. After looking into it further, it turns out that the magnetic poles really are arranged in alternating strips.
Image courtesy of: Magnet Sheet Workshop Visit date (2026/09/11)
https://www.magnetsheet.net/info/index.html
Apparently, magnets can also have many different arrangements of their magnetic poles. I had no idea that such a seemingly ordinary magnetic sheet could contain such a cleverly designed pattern of magnetic poles. Science is full of surprises! Why not try this experiment at home? If you simply want to experience the strange resistance in step ③, you can feel it almost instantly!
Update: I also contributed to the writing and editing of this experiment for Success 15, “Why? How? Science Experiment Workshop.” If you’re interested, please take a look.
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