What device or machine could we come up or make using a simple electric generator?
Electric generators are not simple and a proper design requires engineering analysis. That being said take a look at the alternator found on cars. They can be obtained inexpensively and have several features that make hacking the hardware interesting. Basically it is a three phase machine that can be operated as an AC generator. It also has a built in rectifier that allows it to provide a DC output. The user has access to the field through brushes and can therefore control the generated voltage over a fairly large range. It would be difficult to come up with a more interesting generator.
