I was screwing around with some of the motors from my old Lego Mindstorms kit, and discovered that when two motors were directly connected to one another the spinning of one would cause the other to spin too. It was obvious once I realized what was going on, but still strange to see the other motor spinning without being connected to anything but the other motor.
Step 1: Parts
Step 2: Procedure
If you are demonstrating on another motor:
-connect the power wire to another motor with a wheel on it.
-spin one of the wheels and notice how the other wheel will spin
-to get the wheel to spin in the other direction reverse the polarity of the wire connections by unplugging the square connector and plugging it back in facing the other direction
If you are demonstrating on a potentiometer:
-connect the square power piece on the end of the wire to the 2 leads from the potentiometer
-set it to 20v dc and spin the wheel as hard as you can, from just running it on the desk the highest I generated was 19v
-optional: connect the motor to a dremel or a power drill and see how much voltage you can get it to generate
If you are demonstrating with a LED:
-connect the square power piece to the LED (I used the same LEDs that were used for the throwies)
-spin the wheel, the LED should light up, if not check polarity