ELECTRICAL MACHINERY 477 



rent is produced and when the armature is cutting the 

 greatest number of lines of force the current is at a 

 maximum. When the armature is turned through the 

 remaining 180 of the revolution the same action takes 

 place. As the side AD moves down the current flows in 

 the direction indicated, but as the side BC moves down it 

 is reversed. Hence for one half of the revolution the cur- 

 rent flows in one direction and for the other half it flows 

 in the opposite direction. One end of the coil is attached 

 to the metal ring E, and the other end is attached to the 

 ring F. Both rings are fixed to the shaft, so they rotate 

 with it. 



Brushes C and H are in continual contact with the rings, 

 so the current is taken from them and carried over the 

 circuit. 



Armature. It might be assumed that the iron part of 

 an armature of a dynamo is only to carry the numerous 

 wires which are used for cutting the magnetic lines of 

 force, but this is not the only use for the iron core. The 

 iron carries the magnetic lines of force very much bet- 

 ter than they travel through air, and for this reason the 



FIG. 357 



FIG. 358 MAGNETO ARMATURE 



air space between the fields is as nearly filled with the 

 armature as possible. Fig. 357 shows the path of the 

 magnetic lines through a ring armature. 



