Dc Motor - Homemade
To illustrate possibly the world's simplest motor.
Mounted battery and rotationg coil with carefully polished lead wires.
A small coil is mounted across the terminals of a battery as shown. The enamel is scraped off half of the coil wire where it contacts the battery terminals. The magnet is oriented such that when the coil is rotating it either pushes away or pulls toward the magnet in the appropriate part of its cycle. The other half-cycle the enamel prevents the coil from being activated; if it were it would counteract the torque which produces the desired rotation.