Recent Posts

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. 

Tesla's Plasma Mug

This plasma mug was sold in the 1990s but can be found on eBay often:
From eBay: BUY NOW: Plasma Mug

An improved and beautiful version sold here:
From Etsy: BUY NOW: Plasma Mug

Tesla’s Plasma Mug: this double walled glass mug glows orange from the excitation spectrum of neon gas at low pressure. The base contains a high frequency transformer that generates high voltage electric fields (but at very low current) from 8 AA batteries- which excites the neon to glow, and also serves as a coaster. This crazy item was produced by Can You Imagine Toys in the 1990s- perhaps Tesla himself would have served a good beer in this mug! 

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.


Ambiguous Object Illusion Mug

From Etsy: BUY NOW Squirkle Mug Ambiguous Object Illusion 

These type of objects were invented by mathematician Kokichi Sugihara, and you can buy his books here: 
From Amazon: BUY NOW Ambiguous Objects by Kokichi Sugihara 

From Amazon (Japan): BUY NOW set of four ambiguous objects with booklet 
This kit contains four white plastic illusion objects (including the arrow) and a booklet. I used the translate feature in the Chrome browser to place my order and it shipped to California in a few days. 

The math and physics are described here in this technical journal article by Prof. Sugihara

Ambiguous Object Illusion Mug: circle or a square? It’s all a matter of perspective and viewing angle. The complex shape allows for both to be perceived and is based on the work of mathematician Kokichi Sugihara of Meiji University in Japan, the inventor of this illusion and art form. 

Magneview Flim

Get some magnetic viewing film here: 
From Educational Innovations: BUY NOW Magnetic Viewing Film 

Magneview Flim: making the invisible visible and revealing the hidden physics of our everyday world. Microscopic cavities in this green film are filled with oil and tiny flakes of Nickel metal- like compass needles, the flakes align with the magnetic fields revealing the complexity of the north and south pole domains of these magnets. Two of the disk magnets have multiple north and south poles and look like gears with teeth- these are rotors from small motors. 

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!


Magnetic Newton's Cradle

This magnetic version fo Newton's cradle is no lomnger in production, but somtimes found on ebay:
From eBay: Search NOW: Magnetic Newon's Cradle

Here are some nice versions of the classic Newton's Cradle 
and here is a nice Magnetic Replusion Demonstration

Magnetic Newton's Cradle: the famous collision demonstration reimagined with opposing magnets as the pendulum weights- shown here in two modes of operation. Initially the collision pattern looks similar to the traditional colliding spheres version but quickly goes chaotic- the magnetic field of each weight interacts with all the other magnets simultaneously making the system nonlinear. A 1990s desk toy by Fascinations- sadly no longer in production. 

Sun Sculpture: Magnetic Field Lines of the Solar Corona

This wonderful 3D rendering of the Sun available here:

From Etsy: BUY NOW: Sun Sculpture

See more 3D laser astronomy/astrophysics sculptures here

Solar Sculpture: the paths of 5000 magnetic field lines etched into optical quality glass map the complex flow of plasma in the Sun’s outermost atmosphere replicating how the solar corona appeared on Oct 21, 2000. This sculpture is based on a sophisticated computer model from a group of research scientists at the Lockheed Martin Solar and Astrophysics Laboratory, and the rendering contains 300,000 etched points to create the image. A map of our wonderful and complex star that can be held in the palm of your hand.

 

Universe Sphere

Created by Clemens & Christoph of CinkS labs: Available in a cube too! 
From CinkS Labs: BUY NOW Universe Sphere

Special offer for physicsfun folowers: Use code POCKETUS and get a free Pocket Universe with your order of a sphere. Just add the Pocket Universe to your cart and apply the code. 

Wikipedia has a good description of the distribution of galaxies on this scale 

Click here for Milky Way in a Sphere

Universe Sphere: 380000 laser etched dots, each dot representing a galaxy of stars, reveals the largest scale structure of our universe. This glass sphere contains a 3D mapping of galaxies in a volume of our universe spanning 800 million lightyears in diameter, and shows the clumping and distribution as seen by automated telescopic surveys such as that found in the Sloan Digital Sky Survey data. Hold a chunk of the universe in your hand!


Electric Motor

Get this easy to assemble kit here: 
From Educational Innovations: BUY NOW Simplest Motor Kit 

Electric Motor: in its simplest form!- coil, magnet, and battery. The wire of the coil has an insulating coating- and this coating is carefully scrapped off one side on each end. When current passes through the coil it becomes an electromagnet and the permanent magnet repels it making it spin- as it turns the currents goes on and off depending if the copper posts are in contact with the bare wire (current on) or the still insulated wire (current off). I have motors with fewer parts- but they operate on more complex principles.

Am-241 in Wilson Cloud Chamber

I found this vintage apparatus on eBay. Here is a similar device made for classroom demonstrations (a bit pricey though): 
From Amazon: BUY NOW 
Wilson Cloud Chamber 


Diffusion cloud chambers use dry ice and are more affordable: 
From Etsy: BUY NOW 
Diffusion Cloud Chamber 


Wikipedia has nice descriptions of Am-241 and the history and operation of Wilson Cloud Chambers 

Am-241 in Wilson Cloud Chamber: the typically invisible ionization tracks of alpha particles emitted from a radioactive source are revealed in this miniature expansion type cloud chamber. When an americium nuclei disintegrates it ejects a high speed cluster of protons and neutrons (2 of each) called an alpha particle which then plows through the air creating a trail of ions, tearing electrons off any nearby molecules it passes by. A rapid decrease of pressure (releasing the squeeze bulb) drops the temperature in this chamber allowing cloud formation. Alcohol droplets prefer to condense on ionized molecules/atoms and so reveal the tracks. Amazingly the synthetic element americium-241 is found in common smoke detectors, where a few micrograms will emit thousands of alphas per second. Of course please use great caution if you choose to mess around with any Am-241- it’s safe inside the smoke detector, much less so if removed. 

Bubble Trouble Puzzle

This hard to find puzzle is sold as a magic trick here: 
From magicorum.com: Bubble Puzzle 

See more physics puzzles: featured physics based puzzles

Bubble Trouble Puzzle: physics brain teaser- the trick here is to move all air bubbles to the center bulb. As with all puzzles featured here on @physicsfun, the solution relies on some fun basic physics principles- can you figure out which ones? Answer below and swipe to reveal solution.


Dot Animation Card

Five animations to choose from- collect them all!

From Art fo Play: BUY NOW: Dot Animation Cards

Dot Animation Cards: a unique version of barrier-grid (kinegram) animation where a matrix of holes allows only some of the dots on the covered card to show in succession producing the appearance of motion. In this clever design rotating the card with dots by 180 degrees reveals a second animation. Affordable kinetic art by Shigeki Naito that plays on the psychophysics of vision.

Time's Up

Similar timers available from these sources: 
From eBay: BUY NOW 
Inverted Timer 


From Amazon: BUY NOW 
Inverted Timer 


Time's Up: inverse of the sandglass- tiny plastic beads are less dense than the water and thus ascend to the top of the container under the influence of a buoyant force in accordance with Archimedes' principle. This timer takes almost exactly 6 minutes to complete shown here at normal speed for the first half of this video, and the second half is condensed to 24 seconds in time-lapse. 


Impossible Arrow

One of many creative illusions and curiosities of Victoria Skye. See her work here:

Visit Now: Victoria's Illusion Art

Click here for to explore more "impossible objects" 

Impossible Arrow: an arrow made of wood through the center of standard steel hex nut. The arrow was carved and somehow placed through the nut- neither the wood nor the steel nut was cut or glued to produce this object. Not impossible, but creating this does depend on the use of some obscure physical properties of wood (similar to the impossible nail sculpture). 

Spin Bank

Available from these fine sources: 
From Amazon: BUY NOW 
Coin Spin Bank 

From eBay: BUY NOW 
Spin Coin Bank

Spin Bank: a clever spring mechanism launches each coin into rotation along a symmetry axis on to a concave trapping surface. Angular momentum of the spinning quarter keeps it upright even as it bounces upon impact with the platform. Another spin on making saving spare change fun!