[Diato556] made a really cool single-phase induction motor with parts mounted on Duplo blocks. He has posted an Instructable where he uses these modular parts to demonstrate the motor and the principles of induction as described after the jump.
[Diato556] starts with an AC generator, a tiny alternator made with the coil from a relay and the magnet from a bicycle dynamo. He rotates the magnet on a spit in front of the relay coil, producing an induced current that lights an LED connected to the relay.
Rotating magnetic field
Next up is a rotating magnetic field demonstration. Using the same rotisserie magnet, he induces a current in a rotor made from a small aluminium cylinder. The cylinder pivots against a nail and induced current causes the rotor to spin.
The induction motor builds from previous experiment. Instead of the magnet, the two coils induce current in the rotor. One is fed directly from 12VAC, and the other coil’s power is delayed with a 4.7μF capacitor. The alternating magnetic field causes the rotor to spin.
This is a neat project on so many levels. The modular Duplo-entrenched parts are just plain cool. Give demonstrations at the office, or just keep it around as a fun desk toy or conversation piece. If you don’t have a desk and must carry your conversation pieces on your person, you can’t go wrong with this induction flashlight.