Eddy currents

What you can do here
Lift both discs upwards and drop them freely.
Watch the speed at which they move.

How it works
One of the discs is a magnet, the other is made of aluminium. The only force acting on the aluminium disk is a gravitational force – that is why it drops quickly. Something else happens to the magnet. The magnetic field of the moving magnet induces the so-called eddy currents in the copper pipe. They, in turn, are the source of a magnetic field with such a direction and sense of a vector that the interaction of magnetic fields results in slowing the movement of the disk.

Interesting facts
The induction of eddy currents by an oscillating magnetic field is used in the so-called induction cookers.

Dangerous for people with artificial pacemakers!
Do not put your phone next to the magnet!
Do not put your fingers on the base of the device!