A Diamagnetic Demonstration

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Our friends stopped by with a simple apparatus to demonstrate the diamagnetic properties of bismuth metal. Diamagnetism is a extremely weak magnetic effect — generally orders of magnitude weaker than everyday permanent magnets, which exhibit ferromagnetism. However it is also an extremely interesting effect because diamagnetic materials are repelled by magnetic fields. This is different than the case with ferromagnets, where one pole of a magnet repels another — rather, the entire material is (weakly) repelled by any magnetic pole.

Now, how might one observe such a weak effect? One way is to build a magnetic levitation rig, but the field configurations there are a little less obvious. With a simple but sensitive balance, we can see the repulsion directly. The balance above has a long wooden beam, a central pivot on two blocks of plastic, and a couple of coins on the far end for counterbalance.

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At the business end of the scale, there is a cylinder of bismuth metal about 1 cm in diameter, held in place by a rubber band. We also have a larger rectangular block, which is our test magnet, made of grade N50 NdFeB and painted black. And finally, the Lego Astronaut Twins are here helping out as a scale and position reference.

Moving the block magnet beneath the bismuth, we can see what happens in an animated GIF:
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After the balance settles, the resting position of the end with the bismuth is considerably higher. With some calibration in terms of weights and/or positions, one could even measure the exerted force with some precision.

A slight improvement to this apparatus would be to reverse the roles of the bismuth and the block magnet. That is, to affix the magnet to the arm of the balance, and to slide the bismuth beneath it instead. You could then use a nearby block of aluminum to damp the motion of the beam through magnetic (eddy current) damping. Many commercial balance-beam type scales already use magnetic damping so that they settle down to their final values faster.

 

Hard Drive Earrings

Wearing my new earrings

The newest in my collection of geeky jewelry: glass hard drive platter earrings.

tiny platters

We picked up a tray of tiny glass platters at a local surplus shop some time ago, marked “Tear Down Qty: 25 pcs.”

CF card for comparison

These one inch platters were used in Microdrives, which were designed to fit into CompactFlash card slots. (Shown with CompactFlash card above for scale.) They were used in (among other things) the iPod mini. After 2006, CF cards outpaced the capacity of the fragile Microdrives, and they’re no longer manufactured.

Earrings

The platters are attached to the earring hooks with magnet wire. They’re incredibly reflective, and everywhere I wear them, spots of light are dancing around me.


Related: Hard Drive Wind Chimes

The Tenth Bay Area Maker Faire

10 years of Maker Faire Panel

The 10th Bay Area Maker Faire was absolutely awesome. We reconnected with old friends, made new ones, and talked a whole lot. Above, my panelists talking about the past ten years of Maker Faire. Below, Windell talking about his new book, The Annotated Build It Yourself Science Laboratory. We saw many amazing things, some of which we captured with our camera sensor and have posted in a flickr album here.

Build-it-Yourself Science Laboratory

Build It Yourself Science on the Make Blog

Book excerpt on Polarized Light Filters

The Make Blog is featuring some excerpts from The Annotated Build It Yourself Science Laboratory.

In modern times, our contemporary Maker and Maker education movements have helped to rekindle our cultural interest in hands-on education, especially in the STEM and STEAM fields, in a way that hasn’t been seen since the 1960s — which is why it’s such a good time to bring this book back.

Linkdump: May 2015

linux alarm clock

Analog Education and the 555

The article Can Analog Circuits Inspire Budding Engineers? over at Planet Analog discusses preparing students for dealing with real world circuitry by getting them started with analog circuits.

By building, probing, and observing the signals and their changes in these circuits without any code requirements, students can get a real feel for otherwise abstract concepts such as voltage, current, and more.

The author uses examples of projects and kits including our very own Three Fives Kit.

MakerCon 2015

MakerCon is a short conference put on by Maker Media in the week leading up to Maker Faire about the business of making.

Gael with InMoov

3D printing is a common maker topic, and MakerCon brought a few different twists to it. Above is Gael demonstrating InMoov, an open source 3D printed humanoid robot. There was also an incredibly inspiring talk about applications for medical 3D printing by Dr. Glenn Green.

Gigabot print

3D printing can be whimsical as well, as demonstrated by this “25 mm” drill bit by Gigabot.

Strawbees

The folks from Strawbees had built a quadcopter rotor cage with a clever servo actuator for flapping sculptural wings.

Clever flex design

I enjoyed seeing this attractive laser cut living hinge at the BotFactory demo.

Rogue Rover

Rogue Rovers are electric semi-autonomous ATVs designed for agricultural use to reduce farm injuries and pollution.

More pictures from the event are in my flickr album.

The books are in!

Build It Yourself Science Laboratory

The Annotated Build-It-Yourself Science Laboratory has arrived! We’ve got them in stock and are now offering signed copies at our store, too!

“Would you like to know more?” I’ll be speaking about the book at Maker Faire this weekend, on the DIY stage. Scheduled times are Friday at 2:30pm, Saturday at 10:30am, and Sunday at 4pm.