Most DC motors do NOT have slip rings, they have brushes. The brushes, which are stationary, job is to rub against the commutator. The commutator is a ring (you may have thought this was a slip ring) that is split into segments. Opposed pairs of the comutator segments are wired into electro magnets located in the rotating armature which is the part that spins.
So when the brushes connect to a pair of commutator segments a particular electromagnet on the armature turns on and pulls the armature a little to turn it. But as the armature turns the brushes loos contact with that set of commutator segments and that magnet looses power and goes off. Then, as the armature and commutator turns a different set of segments attached to a different electro magnet repeats the process, the armature keeps turning...
So when the brushes connect to a pair of commutator segments a particular electromagnet on the armature turns on and pulls the armature a little to turn it. But as the armature turns the brushes loos contact with that set of commutator segments and that magnet looses power and goes off. Then, as the armature and commutator turns a different set of segments attached to a different electro magnet repeats the process, the armature keeps turning...
