DIY

Homopolar Motor

Fairly simple to make- here are the inexpensive supplies needed to make a few of these motors. 
AA batteries have a diameter of 14.5 mm, so a bottom magnet with a diameter of 15 mm is just right: 
From eBay: BUY NOW Neodymium Disk Magnet 

Wire that looks and works well is just 10 gauge ground wire. Inexpensive and available at any local hardware store-- or order a small quantity here: 
From eBay: BUY NOW 10 gauge Copper Wire 

Wikipedia has some good details on the physics of homopolar motors 

Homopolar Motor: a minimalist electric motor- battery, wire, and magnet. This type of motor does not need a commutator- the polarity of the electromagnetic coil does not need to reverse. The challenge with this design is balancing the coil to center on the battery as it rotates. A favorite DIY physics toy!

Self-Propelled Homopolar Motor on Aluminum Foil Racetrack

I used neodymium disk magnets, small end = 1/2" diameter, Large end = 3/4" diameter. 
From eBay: BUY NOW Disk Magnets for Simple Motor 

Foil Runner Motor assembly diagram: 
Self-Propelled Homopolar Motor on Aluminum Foil Racetrack: A favorite DIY physics toy where disk shaped neodymium magnets supply the static magnetic field for this motor and become the wheels of a very simple vehicle with an AAA battery as the energy source. As soon as both ends make contact with the conducting aluminium foil an electric current will flow which in turn induces a magnetic field underneath the battery assembly. This induced field will then interact with the neodymium magnets on each end causing them to spin- a wonderful example of a motor with minimal components. The racetrack is a cardboard circle from a pizza box covered in kitchen foil.

Floating Rings Illusion: Dr. Manhattan Booth

Created in my shop with these parts:

From Amazon: plastic rings, plastic sphere, blue paint

Inspired by the Phone Booths in the new Watchmen series.

Calling Dr. Manhattan: floating rings illusion device inspired by the recent Watchmen series. Two attached rings appear to roll in an impossible way around an orb, featured in a number of scenes on top of blue interplanetary phone booths in the new Watchmen series. Created in my shop with plastic rings and some blue spray paint. 


Gravity Defying Nail and Magnet

Neodymium magnets will produce the largest gap when suspending a nail.
Please use exterme caution when handling these magnets. 

From Amazon: BUY NOW: Neodymium Super Magnet

Magnetic Defiance of Gravity: a nail suspended between a chain and a powerful neodymium magnet. Ferromagnetic attraction over a distance of many millimeters, and a reminder of the presence of the typically invisible electromagnetic forces all around us. Make your own with a paperclip, string, and a refrigerator magnet- or get a neodymium magnet and see how massive an object you can suspend in air. 

Magnetic Influence on Aluminum

For this demonstration stronger magnets work best:
From Amazon: BUY NOW: Neodymium Magnets

Here is a good small turntable with bearings: 
From Amazon: BUY NOW: Spinning Base

Magnetic Influence on Aluminum: physics puzzler- spin a magnet under a beer can suspended by a thread, and the can will turn. Why? Aluminum is not ferromagnetic, and as shown, magnets are not attracted to the can.  So how does a spinning magnet influence the can to spin? 

 

 

 

Answer: the can spins due to eddy currents induced in the conducting aluminum due to the moving magnetic fields underneath. The eddy currents make the can into a temporary electromagnet that then interacts with the magnets below according to the famous law by Lenz.

Ferromagnetic Interaction

Here is the NdFeB neodymium magnet used in this video:

From Amazon: BUY NOW: Neodymium Disk Magnet

Please use cuation when handeling strong magnets like this one. Small nails, paperclips, staples and other houlshold object made with iron will interact interestingly with the magnetic feild. 

Ferromagnetic Interaction: iron rich nails temporarily become dipole magnets in the presence of an intense magnetic field from a large neodymium super magnet. Here the neodymium disk magnet is set with its north pole pointing up, so the point of each nail becomes a south pole (repelling each other) and the head of each a north pole. Imbued with these temporary induced fields, the nails will try to align themselves with the neodymium dipole’s field like compass needles, and the nails will interact with each other in interesting ways.


The FluoroSphere

The kit includes the UV LED base, elegant glass sphere, and enough fluorescent gel for many repeat lights shows. 

From PyroFarms: BUY NOW: FluoroSphere

From Amazon: BUY NOW: FluoroSphere

The FluoroSphere: intricate and dynamic lights shows are produced within an elegant glass sphere as fluorescent dyes in mineral oil slowly mix into room temperature water. Ultraviolet LEDs (in the base on which the sphere rests) make the dyes glow brightly and reveal the initial nondiffusive mixing structure which includes the phenomena of drops, plumes, and other features of Rayleigh-Taylor instabilities. Shown here, slightly sped up, is the first 8 minutes or so of the process which takes up to half an hour to mix evenly. The green light is characteristic of the famous fluorescein dye.

 

Disappearing Spoon

Gallimum metal and a silicone mold to produce the spoon- available here:

From Amazon: BUY NOW: Gallium Mold Spoon Kit 

Disappearing Spoon: the metal gallium has a melting point of 30°C (86°F) and will melt quickly when exposed to tea temperature hot water- or melt in one’s hand if handled too long. This spoon was made with a silicone mold (swipe to see process), and feels and sounds just like a regular spoon, except solid gallium is brittle and the spoon can shatter like glass if dropped. An amazing parlor trick as well as a classic and historical class demonstration.

Salt Fractionation

All the ingredients are available from your local market/drugstore. The trick is to find a dye that works for acetone, but will not color water- believe it on not blue glitter will color the acetone nicely and not change the salt water. Follow this link for details: 
ChemEd X: Blog of Prof. Tom Kuntzleman 

Of course Amazon has what you will need:

From Amazon: BUY NOW 
acetoneblue glitterfood coloring, cool bottle 

Salt Fractionation: two liquids that won’t stay mixed! Acetone (dyed blue) floats on top of the higher density salt water (dyed orange). Acetone usually dissolves in water through hydrogen bonding interactions, but solubility can be altered. In a process called “salting out” a sufficient amount of salt is dissolved such that the water molecules, which are much more attracted to the resulting Na+ and Cl- ions (through ion-dipole bonds), will then ignore the weaker acetone hydrogen bonds. This results in the spontaneous separation (shown here in real time) of the liquids no matter how well shaken up. 


Curie Point Heat Engine

This DIY project is pretty easy to build. One half of one of these inexpensive magnetic necklace clasps will work well for the heated magnet. 

From Amazon: BUYNOW: magnet for curie point engine

Curie Point Heat Engine: when the magnet on the end of the wire heats up to a particular temperature (the Curie point) its magnetic field is temporarily lost until it cools. This engine design uses a second magnet to pull the swinging magnet back into the heat source once the magnetic field is reestablished. Repetition of this process creates mechanical motion as long as the heat source is fueled.

Popsicle Stick Bomb

Craft sticke work great:

From Amazon: BUY NOW: Stick Bomb Supplies

Amazingly: There is a Wikipedia entry on Stick Bombs and their physics

Popsicle Stick Bomb: a form of simple tensegrity, the elastic potential energy of the bent sticks is dramatically released under application of a slight concussive force such as an impact with a table top- shown here in forward and backward slow motion (swipe to see three more explosions). Shown here is one of the simplest constructions with 5 flat sticks woven into a spring-loaded configuration held in place by friction and tension induced by the bending of the wood. A nice demonstration of energy conversion- potential to kinetic.

Wringing Guage Blocks

Guage block sets can be a bit pricy, but some fairly inexpensive pieces and small sets can be found for demonstrations and such:

From Amazon: BUY NOW: Gauge Blocks

Wikipedia has a nice description of Gauge Blocks and the Phenomenon of Wringing

Wringing Gauge Blocks: two blocks of metal (not magnets!) will stick together by a process called wringing if their surfaces are flat to high precision- such as these gauge blocks found in most machine shops. Here two blocks are forced apart with a snap, and then wrung back together with the characteristic sliding motion technique. Gauge blocks are flat to less that one millionth of a meter and are used by machinists for precision length measurements and calibration. The science of the wring force remains somewhat a mystery and no one has yet found a fully excepted physics description- but we do know that blocks will wring in a vacuum and that the force can be up to 30 times that of weight of the blocks. Fun physics from the shop!


Volta’s Hailstorm and Electrophorus

This inexpensive electrophorus set works great! 
From Amazon: BUY NOW Electrophorus Demonstration Set 

The container is just the middle part cut from a plastic water bottle, and the "hail" stones are Styrofoam craft beads: 
From Amazon: BUY NOW Styrofoam Craft Beads 

For Volta's Hailstorm to work, the beads must be coated with a conducting spray (here is what I used): 
From Amazon: BUY NOW Staticide Spray 

Wikipedia has a very nice description of the physics of the Electrophorus and how it is used to transfer electric charge. 

Volta’s Hailstorm and Electrophorus: electrical forces due to electrostatic charge send foam beads flying in this version of the historic demonstration by physicist Alessandro Volta. The beads are covered with an electrically conductive coating allowing them to transfer charge from the environment to the plate of the electrophorus. The acrylic platform becomes negatively charged when rubbed with a paper napkin, but it is also an insulator so the charge on it can not flow on to the aluminum plate of the electrophorus. Instead the charge on the platform pushes electrons to the top of the plate (like signs repel) and touching the plate results in a spark that removes the electrons giving the plate a significant positive charge that will then attract the beads.