TROLLEY CARS 



231 



an actual motor 1 a device is employed by means, of which the 

 helix is capable of continued rotation around its support. 



The rotating coil is usually spoken of as the armature, and 

 the large magnet as the field magnet. 



If a wheel is attached to the rotating coil, weights can be 

 lifted, and if a belt is attached to the wheel, 

 the motion of the rotating helix can be 

 transferred to machinery for practical use. 

 The motion of the blades of an electric fan 

 which gives us comfort on hot summer 

 days is derived from the rotary motion of 

 the motor (Fig. 102). 



Trolley cars. A motor constructed 

 with only a single coil of wire in its arma- 

 ture, rotates too slowly and with too little 

 force for practical use. If a motor is to 

 be of real service, its armature must rotate 

 with sufficient strength to impart motion to the wheels of trolley 



FIG. 102. An electric 

 fan. 



FIG. 103. A modern electric power plant. 



1 IrV the actual motor, the reversal of the current is secured by a simple 

 mechanical device, called a commutator. 



