Help understanding an electronic motor

[analyze]

I'm trying to use a motor that I took out of a shredder. It work fine but I can't figure out what the wires all do. As you can see in the picture, the red and the yellow wires are pos and neg and go into the motor. The black and the white wires go to something that sits atop the motor. They point to small circles that are on either side of a tight coil of wire.

When I connect only the red and yellow wires it sounds like it wants to start but doesn't spin. What do I need to do with the white and black wires? I'm scared to just hook them up to a random pos & neg.

Thanks for your help.

 

[FvM]

No specific electronic component is recognizable in the picture.

It's a wound field DC motor, typically operated with armature (black and white cables to the brushes respectively "something that sits atop the motor") and field winding (red and yellow cables) series connected, without electronic control. It can work with AC and DC as well (it's called universal motor thus), but the dimensioning is for AC mains voltage, usually.

Apart from direct power supply, there are different modes of electronic control, either using the said basic series circuit or an independant supply of field winding and armature.

Anyway, the motor can't generate torque without powering both armature and field winding.

 

[analyze]

Thanks. I clearly don't know much but I think you've told me what I need to know.