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Watch a Powerful Electromagnet Shrink a Quarter Down to Half Its Size

Remember when we saw Physics Girl explode a soda can in half thanks to the power of electromagnets? In that same video, Dianna Cowern also showed us how the same device could shrink a quarter to half its size. No, this wasn’t some sort of trick coin or magical switcheroo (a new high-speed camera actually captures the coin shrinking). It was just a display of the awesome power of physics. So what’s going on here?

Joe Diprima from ArcAttack chimed in on the discussion, since he designed the electromagnetic coin-shrinking rig like a modern-day Dr. Frankenstein. The machine features a 160-pound capacitor—a “big battery”—that maxes out at 8,000 volts! (That’s 72 times the voltage of your wall outlet.) The circuit in this machine is completed by two brass balls positioned just close enough to generate a spark between them, and a bleeder resistor is also added to make sure that any leftover (potentially lethal) charge is eliminated.


Faraday’s law of induction, as explained by Physics Girl

The coin itself is wrapped in a copper coil so that, when current runs through this coil, a straight, parallel magnetic field is generated inside of it (thanks to Faraday’s law of induction), right where the quarter is. While the actual coil won’t get to the point of maximum theoretical magnetic force (since it explodes), it does max out at around 50,000 amps, i.e. in the range of a lightning bolt’s level of current. As the current ramps up, so does the strength of the magnetic field; the crazy thing is that the magnetic field also induces a current in the quarter itself, to the tune of 138,000 amps, 192 Volts, and nearly 26.5 million Watts. And because the particles of the quarter experience electric and magnetic fields, the coin is subjected to the Lorentz force from all sides, and thus evenly shrinks inward. Because Science!

There’s also a very cool gallery over at Captured Lightning, which was mentioned in the video, that shows all sorts of shrunken coins and even offers them up for sale…which is the much safer alternative to adding one to your collection, so don’t try this at home.

Are there any other forms of currency you’d like to see shrunk? Would you rather find out how to make your money grow instead? Let us know in the comments below!

Images: Physics Girl/Youtube

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