Fig 2Brushed DC, cap off6 brush switches per turn4.0 rpm
armature angle 0°brush switches so far 0per turn 6
N: magnet, or a pole made north by its coilS: magnet, or a pole made southCoils carrying most of the currentCopper drum on the shaft: the commutator. Dark blocks touching it: the brushesTwo magnets, three wound poles, and a commutator split into three segments. The brushes feed current into whichever segments they touch, so the poles are always magnetised to be pulled toward the opposite magnet. Just before a pole gets there, its segment slides under the other brush and its current reverses. That happens six times per turn, and the flash at a brush marks each switch. The scope shows each coil's current stepping between full, partial and reversed.