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Recently Hackerbot Labs was invited by Intellectual Ventures to demonstrate their Maker Faire Editor's Choice Award-winning high voltage coin shrinker in front of a Vision Research Phantom 100k fps high-speed camera.

Discharging about 10 kV (15,000 joules!) from enormous 300 µF capacitors the team at Hackerbot Labs "Turn half dollars into quarters! Turn quarters into dimes! Turn dimes into little semi-molten balls of metal!" with their custom built apparatus through a process known as "Magnaforming".

Passing current through a coil of wire produces a magnetic field. In this case, with so much current, the magnetic field produced is gigantic: the coil becomes a magnificently powerful electromagnet.

The creation of a magnetic field in the coil-now-magnet induces a circling current to flow around the coin sitting inside the coil. This current in the coin also produces a magnetic field (i.e., the coin becomes another electromagnet). The kicker is that the coin's magnetic field and the coil's magnetic field point in opposite directions, so the coin and the coil repel each other furiously.

This repulsion creates forces which overcome the strength of the metal; the coil is expanded out and explodes, and the coin is pushed in and shrunk.

Some interesting facts were gathered as a result of the demonstration:

• Filmed at 100,000 fps, the coin will shrink in just 30-40 microseconds


• The coin will have shrunk prior to the coil exploding


• A loud 135 dB shockwave is produced as the coil explodes


• When shrinking the edge of the coin moves at about 400 mph

High Speed Coin Shrinking [via Intellectual Ventures]