The experiment takes place at the Palais de la Decouverte in Paris. A huge electromagnet is supplied with an astonishing 800 amperes of alternating current at a frequency of 900 Hz!!! On top is an aluminum disk which weight one kilogram.
It all started one day when Faraday created his famous induction ring, by winding two coils of insulated wire onto an iron ring. When he provided DC power to one coil, a small pulse of current was induced in the other. When the power was disconnected, current was induced in the other direction. In modern days we know this as a transformer!
Today we know that AC current creates a continually changing magnetic field, and that a magnetic field can create a continually changing electric current (AC). After all, this is exactly how transformers work: The primary coil creates an alternating magnetic field by the alternating current that we provide. This field is coupled through the iron core of the transformer with the secondary coil. As a result, an alternating current appears at the secondary coil due to this electromagnetic field.
Now, if we short-circuit the secondary coil of the transformer, alternating current will run though it. This will eventually create a secondary magnetic field which is opposite to the magnetic filed that was created from (primary coil). If we cut the iron core in half and separate the primary and the secondary coils apart, what we will notice is that the opposite magnetic fields will repeal each-other.
This is exactly what happens with the aluminum disk: A strong magnetic field is created by the massive 900 amperes of current. This magnetic filed is induced to the aluminum disk, which acts as a secondary coil. On the disk, alternating current is induced which generates an opposite magnetic field...