This experiment helps to bridge the gap between electricity and magnetism. Below is an electromagnet. Nothing particularly spectacular about it as it is right here.
It has almost no inherent magnetism. This particular model consists of wires wound around a steel U-shaped bar. The two sides are wound around in opposite directions. Basically, these are two solenoids wounds in opposite direction.
Once the current is turned on, it flows through the coils, which creates magnetic fields in the direction determined by the right hand rule (curl your fingers in the direction of the current and your thumb points in the direction of the magnetic field). Since the two sides are set up in opposite directions, one side acts as a "north" pole and the other a "south."
There is also the battery-powered model: