198 



APPLIED SCIENCE 



coil so that the armature must again rotate a half -revolution 

 in order to include the greatest number of lines of force. Each 

 turn of wire acts in the same way, so that the continual 

 force acting on the armature causes it to rotate. By means 



FIG. 89. Brush- 

 Holders. 



Fio. 90. Poles of a Multi-Pole 

 Dynamo. 



of shaft and pulley, the energy may be transmitted to other 

 machines and made to do work. The direction in which a 

 motor runs may be reversed by changing the connection so 

 that the direction of current is reversed through either field 

 or armature. 



241. Kinds of Motors. There are different kinds of 

 motors as there are dynamos. Series motors are used in 

 hoists, cranes, railways, etc., where it is necessary to start 

 with a full load and where the automatic regulation of speed 

 is not necessary. Shunt motors are used when automatic 



