Build Your Own Electric Motor

This Sunday Zach comes into my room asking about how he can further his plans to build his own space ship. He was looking for motors and wings and combustibles. Boy is ready to go. After some discussion, he asked “Dad, I understand electricity, and how power gets to motors and batteries and lights, but how does the electricity make the motor turn?”
I hearkened back to my physics class days and remembered building my own motors out of nails, dowels, and simple power sources. A little digging on the net brought us to this series of pages, where you could assemble a small motor in about an hour using some wire, paperclips, a magnet, and a battery.
Zach was all over it, and about an hour later, we happily had a spinning rotor running on my desk. He understood how brushes are used to reverse the polarity of the rotor as it passes the magnet, and we had an example of a wire coil acting as an electromagnet. We also had a direct example of what happens when a motor gets power applied to it but is not actually turning, in the form of nice curling smoke. That was a nice object lesson, for sure.
All in all, a really interesting exercise, and I still like seeing the little spinning wire object whirring away. “I made that. Cool.”