How to Shrink a Quarter with Electricity

I think it's called "magnetoconstriction" and whenever the forces acting on a piece of metal, even if due to the increase in the intensity of a magnetic field penetrating it, get high enough, the metal will begin to behavior like a fluid and can deform.  You could get the same effect by just clamping a coin between two metal cylinders with a slightly smaller diameter than the coin and hammering the edges of the coin inward.  Then you would remove the coin and repeat the procedure using two metal cylinders with a slightly smaller diameter and so on until you got the coin down to the size you wanted.  That is how skilled jewelers would do it.

Btw.  Title 18 , Section 331 of the United States code provides *criminal penalties* for anyone who fraudulently alters, defaces, mutilates, impairs, diminishes, falsifies, scales, or lightens any of the coins coined at the Mints of the United States.  I guess if someone got caught doing this to US coins, he could claim it was not for fraudulent purposes, but, rather, for artistic or scientific puposes.  Hopefully, his judge would agree with him!