Using an alternator off of a car there is no problem. The
alternator has diodes in it that rectify the AC to DC.
Old generators on cars used brushes to do the job, but
after the development of diodes that would do the job it
got a whole lot better.
Bill Gill
Bill is quite right. A car alternator bought from a scrap yard. Will generate an AC current/voltage when turned by an external source. (14 volts at 15 Amps say)
All AC motors when turned externally....will produce an AC voltage/current..
Those AC motors that do not have Magnets surounding the
rotor, will have a seperate field winding (surounding the rotor). Their Field winding may need to be connected to a 6v-12 volt battery ....to provide the required Magnetic field.
However all DC motors, especially small model car motors, model train motors and similar...all have Magnets surounding their rotor. So if you connect a DC voltage to them of between 3-12 volts, they will run at quite a High speed.
Now all these type of Model motors will generate a DC output voltage, when driven externally.
A bicycle , or a propellor fixed to its shaft will generate the equivalent Voltage (that the motor originaly used to run with) back. If you only use a low powered item like a torch bulb, The motor will turn in a light wind, and lite the bulb. A heavier load will make your model motor progressivly harder to turn.
Idea-
For a simple experiment...grab a 12volt brushless computer fan...blow a hair dryer into it....It should give out a + or - ve voltage dependent on which way you use the hair dryer to blow the 'puter fan round. It will only output a few milli-amps ...check it out with your DC voltmeter.
