(b) The construction of DC generator is almost same as AC generator. The only difference is presence of split rings (DC Generator) in place of circular rings (AC Generator). The split ring works as commutator. The split ring is a metallic ring with two equal parts, i.e. C1 and C2. One end of armature is connected to one part of C2 while another end of armature is connected to another part of C2. The splits rings C1and C2 touch the brushes B1 and B2.
(c) Working of Commutator: When armature is rotated in the magnetic field then electric current is induced in armature. The position of brushes B: and B2 is coordinated in such a way that after every half cycle of armature, the brushes keep on changing connections from one split ring to another split ring. This helps in maintain the current in a single direction even after each half cycle of armature.
Let us assume that in the first half cycle, the direction of current makes the ring C1 as positive terminal and C2 as negative terminal. This makes the brush B1 as positive terminal and B2 as negative terminal. In the next half cycle, direction of coil changes and C1 becomes negative while C2 becomes positive. At the same time, C1 comes in contact of B2 while C2 comes in contact of B1 Thus, B1 always remains positive and B2 always remains negative. Due to this, current always flows from B1 to B2.
