It’s an electromagnet pendulum analog circuit ... with electromagnets so they can move on to the next logical steps: coil guns and web shooters.

The key interaction is between a permanent magnet mounted to the end of the waving arm/pendulum and a many-turn wire coil attached to ... combining simple design and fabrication with just enough ...

A coil with an iron core is called an electromagnet. The iron core increases the coil’s magnetic field strength. A simple electromagnet is made by coiling wire around an iron nail. An iron core ...

A coil of wire, or solenoid, consists of a wire coiled up into a spiral shape. When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet.