Justin describes how to build a DIY four part motor. It requires a battery, a wire, a screw, and a small disc magnet. The hardest part is getting the screw to hang from the battery.

The way this motor works (as shown below) is by creating a closed circuit, where the current actually flows through the magnet. When this happens, a magnetic force turns the magnet, which spins the screw.

He also posted a Google video of the motor in action. This project has always been great for procrastination or entertaining youngsters.