Tuesday, May 06, 2008

Fun with Magnets

Last week, my brother had started to tidy up a cupboard at our parent's place where we had stored away toys and other stuff from our childhood. In between chemistry and electronics kits, he dug out a small orange box I had completely forgotten about, but which I had loved when I was a small boy: A kit with a few magnets.

There was a magnet with a grip that can be used to lift coins and paper clips, two funny plastic spheres with bar magnets hidden inside, and two rings of magnetic material. The only thing missing was the little jar with iron filings to map out magnetic field lines - but I remember that my mother once had removed it from the kit, because she had become fed up with this stuff ending up either distributed all over the kitchen or sticking to the magnets.




These ring magnets were especially fascinating because one of them could be made hovering above the other on a pole, and oscillate along the pole when dropped.

The most surprising effect I could create with the oscillating magnets I had discovered by chance: I could use the magnets to switch off our new, remote-controlled TV set. Physics was cool!




Here are more Cool Experiments with Magnets. Unfortunately, understanding the origin of the "itinerant ferromagnetism" of the classical permanent magnets, iron, cobalt, and nickel, is not that easy, but interesting nevertheless.


14 comments:

Bee said...

:-) Very nice. I think this is actually the same company that I had the electronic sets of (previously mentioned here). I probably should have know it was written with a 'k' not a 'c'. And with the right spelling one can then also find out that the brand still exists...

Phil Warnell said...

Hi Stefan,

A neat little introduction set for magnetism and perhaps one that you should send along to our confused friend at Discover magazine. Although you have to include some paper and iron filings as he may then recognize the field as to be something that to a large part can be comprehended. Come to think of it I wouldn’t mind having those donut magnets on a stick for my office desk. Then perhaps not for I am already perceived too much as a weirdo :-)

Best,

Phil

Uncle Al said...

Every defunct microwave oven has a large strong ferrite donut Helmoltz pair surrounding its cavity magnetron. Careful disassembly obtains a free prize.

Dipoles attract as 1/r^3. NEVER let strong magnets snap together. Ferrites are especially hazardous for being brittle - spalling and shrapnel.

Andreas said...

Not only does the brand still exist, the set is still sold.

Anonymous said...

A very nice post! Can you explain a little more about how/why you were able to turn off your tv with the magnets?

stefan said...

In order to switch off the TV, I just had to drop the upper magnet along the pole towards the lower one, so that it started to oscillate up and down.

I'm not exactly sure about the mechanism. It did work only with a quite old TV set from the early 1970s, not with more recent ones. This old TV (it had a white casing, but i don't remember the brand or any technical details) already had a remote control - I don't know whether by infrared or radio/microwave link.

But when I think about it today, I am quite sure that the oscillating magnets did not interfere with the remote control - I do not see how the frequencies involved could match. My guess instead is that somehow the changing magnetic field triggered by induction an electromagnetic relay in the TV set, or something like that, which switched it off. That could explain that there is no effect with more recent, all-electronic TV sets. Unfortunately, the old TV doesn't exist anymore, so I cannot check this out.

But the effect was fun :-)


Hi Andreas,

thanks for the link - that's nice that these kits still exist!

Cheers, Stefan

CarlBrannen said...

As an engineer, I bought a Levitron, the spin stabilized floating magnet top, years ago. I should probably blog it. The physics is explained in the peer reviewed literature.

Phil Warnell said...

Hi Carl,

“As an engineer, I bought a Levitron, the spin stabilized floating magnet top, years ago. I should probably blog it. The physics is explained in the peer reviewed literature.”

That’s interesting as I was given one as a Christmas gift several years ago. The trouble is I could never get the darn thing to work. It even came with a battery powered gizmo to spin the thing which apparently the earlier model didn’t have. I never did figure out if the thing was defective or the owner too dumb to read the instructions properly. With sll that said, after I read the paper you refer to that is to explain how it is suppose to work, I might be able to determine which. That is if I can still find the thing:-)

As for it being the fact you’re an engineer that prompted you to buy one is a nice dodge that avoids admitting even older males still enjoy their toys:-) I’ll make you a wager that Stefan won’t part with his now that it’s been rediscovered:-)

Best,

Phil

Plato said...

I've changed my name to protect my innocence:) Another weirdo here:)

Played with the magnets too.

Experimented, to see if they change seedlings. No! Controls don't show this is possible(done at a university level not by me), even though the shuttle carried such seedling above earth for further considerations? This done not imply the contrary just that research was done.

It reminded me of Mesmer, and I thought you had a post here about him Stefan? Maybe it was someplace else. Poor memory:)

I too, had been enamoured with the magnets and of course this lead to the understanding of seeing in a geometrical space, that Gaussian arcs can supply. It's graduation of course to the non-euclidean of those things that are first a mystery, and then, becomes less so.

So seeing "the superconductors" and the floating spinning magnets were ideas about what "friction removed" can now do? Navier Stokes, and then the attributes, of the superfluid could have implied, and what the singularity could have imply?

All speculation of course at this point.

Now looking at the earth itself, it's elemental structure, being capable of? Ya, I know, dreamer:)

But to this end imagine what the future holds?

So what had hidden away, now comes back to remind one of what began as a mystery.

How nice, we recognize our innocence.:)

Plato said...

Ah yes, Mesmer was used in reference too, Happy Birthday Benjamin Franklin

Andrew Thomas said...

Bad luck, Phil. I got my Levitron to work. Here's a Video from the Levitron site.

When you spin it initially, you have to feel it "locked" in position in the centre by the magnets - it doesn't shift from the spot. Then as you gently raise the plastic, it lifts off itself, and then you can slide the plastic away.

I seem to remember it was quite expensive. And when you've done it, you've done it. There's not much incentive to do it over and over. Still, it's fun for an hour or so. I have no idea what it teaches anybody about magnetism!

CarlBrannen said...

"I seem to remember it was quite expensive. And when you've done it, you've done it. There's not much incentive to do it over and over. Still, it's fun for an hour or so. I have no idea what it teaches anybody about magnetism!"

This is about right. I seem to recall that we got it to suspend for 30 seconds. I'd dig it up, but it's really an amusment best reserved for those who haven't already done it.

I think it was about $30 or $50 at the local science shop where I used to buy specimens for my collection of pyrite crystal forms.

The only place I played with it was at work. All the engineers, (electrical and computer science) came and had a go at it.

To get it to work, it had to be tuned. It came with a set of rings to provide weight. Being engineers, of course, we optimized the crap out of this and found that ours worked best with our own adjustments.

I guess I should mention that there is a quite an interesting range of parameter space to optimize over. A top has 3 principle rotation axes (or whatever they call it, it's been 30 years since I took mechanics), plus the weight, and there may be some non trivial effects with air friction not to mention how fast you spin it when you start it off.

As another hint, I should mention that you need to get the base properly level. Rotating the base may have an effect, if the base is not symmetric.

michaeldcassidy said...

run it across your computer screen......

stefan said...

Hi Michael,

run it across your computer screen..

Now.. unfortunately there is no fancy effect with the TFT screens I work at nowadays...

But that reminds me of a curious story at the old physics institute in Frankfurt: In the floor just below my office in the theory department, there was the lab of one of the condensed matter groups, and they must have been working with strong magentic fields... Every now and then, the big cathode ray tube screens we were using as terminals had some distortions and strong red and green shadows in the corners, and it was necessary to degauss them to work without getting instant headache...

Cheers, Stefan