234 



ELEMENTS OF GENERAL SCIENCE 



239. The essential parts of a motor. What changes can be 

 made in the simple motor described above so as to construct 

 a working machine? This question can be answered by a 

 study of the motor shown in figure 119. The electromagnet 

 is turned aside so that the bar magnets can be brought into 



FIG. 119. A small motor 

 This motor is operated by an Edison storage cell 



place on either side of the vertical axle. The bar magnets 

 furnish the magnetic field. A coil of wire mounted on an 

 iron core is placed on the central shaft that can be rotated. 

 The ends of the coil are connected to a metal cylinder stand- 

 ing just above the coil. When the terminals of a single 

 dry cell are attached, the current can pass through the metal 

 brushes to the coil. When the switch is closed, the coil spins 

 quite rapidly. The motor fails to operate, however, when two 



