Build a simple electric motor/generator

(Page still in development)

There are lots of ways to do this. For now, we’re linking to a few other sites that show how. And the motor you build can be used with some of our other projects.

Keep the following in mind:

  • Pick a design that you can crank to use as a generator.
    • This is phenomenally useful for explaining AC power
    • The youth love it.
    • When you hook it up to an analog voltmeter, it’s fun to see the needle swing back and forth
    • Easiest way is to ensure you can add some kind of crank to the central axle
  • Pick something suitable to the level
    • You can go big or go small
  • Can you hook it up to something else?
    • We had some Scouts build one, and hook it up to this small steam engine with the Meccano
    • Could you hook it up to a bicycle and have them pedal?

Homopolar motors (here and here) are really simple, but are useless for anything beyond  a quick demo.

This one is better because you can bend the end of the paper clip to make a crank, remove the battery, and test it as a simple generator with hook up to a voltmeter. This is another variant with a better layout for our purposes.

This design (here, here and here) is better for Scout/Venturer level. Replace the nail with a long length of coat hanger so you can bend it to make a crank handle. Better yet – hook up the nail to a power drill. Pick your central axle size or grind it down so that it can be hooked up to some Meccano or other construction set with gears, pulleys and wheels. And learn to use that voltmeter.

And with an old electric drill, you can do something crazy like this.


  • Are you generating AC or DC? How can you tell? (Hint: looks cool on analog voltmeter)
  • Put a bulb on it. Measure resistance and current
  • Calculate power output ( voltmeter/multimeter to measure current (I) and voltage. P = V x I.
  • Have Scouts and Venturers build different ones with a different number of winding turns. How does it affect the voltage and current flowing through when you hook up a light bulb? (Hint: twice the windings, twice the voltage. But half the current. Do that power calculation.).
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