Science Buddies: "Ask an Expert"

We thought it would be a great idea to get magnetic tape for the track for the mag lev train. The tape attracts both sides of our magnets (doesn't repel the magnets that will be on the train.) Is there anything we can do to make the tape work? thanks.

trinxiegirl wrote:Is there anything we can do to make the tape work?

Good question, but one I can't answer; however, you can run some experiments to find the answer...

1) What happens when you put the magnet side of two pieces of your tape together?
a) If there is an orientation where they repell, the next question is whether there is enough repelling force for your application by using two pieces of tape.
b) If they tend to slide or slip and end up attracted to each other, the orientation of the North and South poles in your magnetic tape isn't going to work for your application. The ususal applications are to attract a piece of steel and not another magnet. Some vendors make "A" and "B" tape that are designed so that an "A" piece will attract a "B" piece which means an "A" will repell an "A" and a "B" will repell a "B" so maybe you could try one of these.

If the magnetic field from your tape is too weak, a strong magnet of either pole is capable of easily overcoming the tape's magnetic field and attracting the base material.

Hope this helps you answer your own question.

trixiegirl - I think the type of magnet you are referring to is the flexible type often called a 'refrigerator' magnet. These are constructed of magnetic material, usually ferric oxide that is mixed with a plastic type binder and magnetized by a source that produces alternating N and S poles in a mosaic pattern. It easily adheres to iron based materials (like refrigerator doors). If you place two similar 'refrigerator' magnets face-to-face and carefully slide them you will feel the alternating attraction/repulsion action as their mosaic patterns align N-N, N-S, S-S and S-N. This quality of a magnetic surface made up of small N and S domains makes for a great way to adhere advertising to refrigerator doors (or bulletin boards) etc., but I don't think it can be a practical solution to a Mag Lev application. Not to say it couldn't be done by an elaborate electromagnetic switching arrangement that commutated the repelling magnet domains (on the vehicle), but that would be cost prohibitive and way beyond the scope of your experiment. Your best solution would be to embed a series of same polarity small permanent magnets on each surface. Tedious, but the only practical way to keep repelling poles producing your levitation effect. Good luck.

Rick Marz