So, magnets, right? For whatever reason, certain kids of a certain age are fascinated by magnets. I know I spent long stretches of time playing with two little toy dogs, no bigger than paper clips, with magnets in their noses that would *snap!* the doggies together in a pooch-smooch. Methinks the appeal of magnets has something to do with the nigh-supernatural way they can make other things move without touching them.
Another popular, seemingly random item that’s also perennially popular with certain kids of a certain age is the compass. Watching the needle spin of its own accord to orient itself to the North and South Poles is another source of considerable fascination. And, of course, magnets and compasses are inextricably linked. But, how does a magnet know which way is which?
New from Bifco®, It’s Magnet-On-A-String™!
For this Demo Science science demo, you’ll need a long piece of string and a bar magnet. (Not a “bar magnet” like a magnet with your favorite pub’s logo on it; a “bar magnet” like a bar-shaped magnet.) Also masking tape, a marker, and maybe a ladder or a chair to stand on.
Tie one end of your string around the center of the magnet. Determine which end is “North” and which end is “South”, and mark them as such with small pieces of tape and a markered “N” and “S”. As reference, mark the area on the floor directly beneath the two ends with similar “N” and “S” bits o’ tape.
Mosey up your ladder or clamber onto your chair and tie or tape the opposite end of the string to a light fixture or other overhead anchor. It doesn’t matter what, really, as long as the magnet end of the string hangs freely and has room to move and swing around sans interference.
Now that it’s hanging down from above, make sure the magnet is properly balanced, and not tilted to either the N or S end. Adjust the string as needed to balance the magnet correctly.
Once you’ve got your Magnet-On-A-String™ all nice and balanced up, have one of your students (not Kevin!) spin the magnet so that it rotates several times, then let it go. This part can be repeated, if desired, A) to give more students the chance to participate, and 2) to show that the results are truly repeatable—a key part of any scientific experimentation. What happens?
Like A Record, Baby
No matter how many times it spins and/or un-spins, your bar magnet will always return to (more or less) its original alignment. After gradually untwisting the rope and eventually coming to a stop, the “N” and “S” poles will end up in the same positions in which they started.
The earth’s magnetic field acts on the freely-hanging magnet just it they does on a compass needle. It influence the magnet’s magneticness to align it with the poles.
Happy Thanksgiving from Demo Science! (Also, wouldn’t “Thxgvg” be a perfectly splendid abbreviation for “Thanksgiving”? Maybe better in all caps: THXGVG. Let’s see if we can make that a thing, gang. Whaddaya say?)
Photo credit: Efraimstochter | Pixabay