Eddy currents

HOW

1. Lift both discs and drop them freely.
2. Note the speed at which they move.

WHY

One of the discs is a magnet, the other is an aluminium disc. The only force that acts on the aluminium disc is the force of gravity. That is why it falls fast. The situation is different with a magnet. When it moves, its magnetic field induces eddy currents in the copper tube. They, in turn, are the source of a magnetic field of such a direction and sense that the interaction of magnetic fields has the effect of slowing down the motion of the disc.

NOTE!

• Dangerous place for people with pacemakers!
• Do not take your phone near the magnet!
• Do not place your fingers on the base of the device!