How to Shrink a Quarter with Electricity

I don't understand your explanation.  You just said the magnetic field shrinks the coin.  That doesn't explain anything.  Metals have a natural density at room conditions.  If you shrink the coin, you have on of the following: 
- Density of coin is increased (please explain the physics of how that happens)
- some metal is vaporizer (removed somehow)
- the dimensions of the coin have changed (thicker so first two above are not in play)

Thank you...