Ans. It consists of a series of copper bars or segments arranged side by side forming a cylinder, and insulated from each other by sheets of mica or other insulating material. [Illustration: FIGS. 174 to 178.--Commutation of the current. These figures show how a dynamo transforms alternating into the so-called direct current. During the first half of the revolution the current flows in the direction A B, out through segment F of the commutator and brush M, returning through brush S and segment G, figs. 174 and 175. At the beginning of the second half of the revolution, fig. 176, the current in the armature reverses and flows around the loop in the direction B A. At this instant the brushes M and S pass the gaps between the commutator segments, thus reversing contact with the segments, and causing the current in the external circuit to remain in the same direction.] =Ques. Where is the commutator placed?= Ans. It is attached to the shaft at the front end of the armature. =Ques. What are inductors?= Ans. The insulated wires wound on the armature core, and in which the electric current is induced. =Ques. How are the inductors connected to the commutator?= Ans. The ends of each conducting loop or coil must be connected with the commutator segments in a certain order to correspond with the type of winding. =Ques. Explain in detail how direct current is obtained in a dynamo.= [Illustration: FIGS. 179 to 181.--Elementary dynamo armatures. Fig. 1, single turn loop; fig. 2, coil of two turns _in series_; fig. 3, coil of two turns _in parallel_. In operation the amplitude or maximum pressure induced with the two turn coil, fig. 180, is double that of a single turn loop, fig. 179. In fig. 180, the pressure is double that induced in fig. 181, while the amount of current generated with series turns, fig. 180, is only half that generated with turns in parallel fig. 181.]