Electric generator not giving resistance

This is related to my previous thread. http://boards.straightdope.com/sdmb/showthread.php?t=796952

I want to experience the effect of a generator being harder to turn when a load is placed on it. So I snagged a battery powered car and pulled two electric motors out of it. Both motors run when attached to a battery, they turn regardless of the polarity of the battery connection. They have a small flat disk capacitor attached to one of the terminals.

When I spin the shaft of the motor (to use as a generator), it spins fairly freely. My thought based on the previous thread is that if I attach the leads together it allow current to flow, the shaft should be harder to physically spin.

It doesn’t. I feel no difference in resistance regardless of the wires being free or attached to something.

What am I doing wrong or what do I not understand? Do the capacitors not allow electricity to flow out of the motors, when spun like a generator?
I’ve wired the two together as well so to induce one to spin when I turn the other (see post 26 of the other thread)… Nada, no spinning of the other motor.

Any pictures? Do they have four terminals or two? We would need to know the construction of the motor to do anything further.

What kind of motors are they? Permanent magnet, brushless, field wound, AC motors? It does matter.

I’ll tryto get pictures in the morning. They are two lead, dc driven. I got them out of a small battery operated toy car. I know nothing else right now about them…and didn’t know there were different types or if it mattered.

The cheap little DC motors found in these toy cars spin at very high speed (>10,000 RPM) and low torque with a large gear reduction to generate enough force to move. Your almost certainly aren’t able to spin the motor fast enough with your fingers to generate any significant voltage. There’s also a minimum amount of voltage needed to get the second motor to even turn at all, due to the cheap bushings used, so you aren’t generating enough voltage to even get the second one to turn.

They both have gears that will mesh together on their shafts. If I attach them and spin one with a battery, will it spin the other one fast enough so that I can notice a difference when I put an electrical load on the second one?

Do some searching for “slot car” & “braking” or “braking circuit”. Slot car racers do exactly what you are wanting to do. Be sure you’re looking at the two-wire permanent magnet motors; I think some use brushless DC motors now.


I’ll try to upload a video soon. Thanks guys especially to AndrewL for the tip that hand spinning doesn’t produce a noticeable effect. Hooking up to a battery spins the motor fast enough.


Whatever you do never do a search for “energetic forum”. You may never be heard from again. :dubious: