TROLLEY CARS 233 



matter how complex these various parts may seem to be, the 

 principle is the same in all of them, and the parts are limited 

 to field magnet, commutator, and armature. 



Nearly all electric street cars (Fig. 104) are set in motion by 

 powerful motors placed under the cars. As the armature ro- 

 tates, its motion is communicated by gears to the wheels, the 

 necessary current reaching the motor through the overhead 

 wires. 



Small motors may be used to great advantage in the home, 

 where they serve to turn the wheels of sewing machines, and to 

 operate washing machines. Vacuum cleaners are frequently 

 run by motors. 



