ELEMENTS OF ELECTRICAL ENGINEERING. 



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Fig. 20. 



Armature current and armature resistance. From Fig. 1 9 it is 

 evident that, of the total current which flows out of the armature 



to the receiving circuit 

 /, half flows through the 

 windings on one side of 

 the ring, and half through 

 the windings on the 

 other side of the ring. 

 That is, the windings on 

 the ring present two 

 paths for the flow of cur- 

 rent from brush b to brush 

 <7, and the current in each 

 path is half of the current 

 which is delivered to the 

 receiving circuit. 

 The resistance of the armature winding between the brushes is 

 one half the resistance of each separate path, since the two paths 

 are similar and in parallel. Furthermore, the resistance of 

 the armature between 

 brushes is one quarter of 

 the resistance of the 

 winding considered as 

 one long coil. 



Closed coil and open 

 coil armatures. The 

 armature winding shown 

 in Fig. 17 is called a 

 closed coil winding, in- 

 asmuch as the winding 

 itself forms a closed cir- 

 cuit. Fig. 2 1 shows the 

 simplest example of what 



is called an open coil winding. It consists of a single coil of 

 wire of which the ends are connected to the two segments 



