Page:Electricity (1912) Kapp.djvu/192

188 second half-wave, the current will be pulsating between zero and a maximum. It is true, the maximum will always have the same sign corresponding with the general sense of flow, but the flow will be extremely irregular, and in some respects, such as the question of flickering, no better than an alternating current. The alteration we need make to get out of the machine shown in Fig. 14 a uni-directed current, or, as it is technically termed, a "direct current" (abbreviation "DC"), is simple enough. We need only, as shown in Fig. 16, replace the two whole rings by one ring split into two halves R1 R2, which are insulated from each other and connected respectively to the two ends of the coil. In Fig. 16 the coil is shown as consisting of only a single turn. This is done to avoid a complicated diagram. In reality the coil would have a large number of turns. The brushes are placed right and left on a horizontal diameter. By applying the right-hand rule it will be seen that with clockwise rotation of the armature, brush B1, is always the negative and B, always the positive brush. The machine therefore gives DC, but a strongly pulsating DC.

In order to smooth out the pulsation to an