ELECTRICAL INVENTIONS 



237 



The remainder of the current goes to a binding-post at d, thence 

 through metal strips that are held in contact with the commutator 

 by their springiness, and out at e. The commutator here con- 

 sists of three pairs of copper strips each insulated from its neigh- 

 bors. The members of each pair are fastened to the opposite 

 sides of the axle of the armature. (See II and III of Fig. 101). 

 The members of each pair are also attached to the ends of a 

 wire wound about one of the radial iron spokes or cores. Thus 

 / and g are attached to the ends of a wire that is wound in a 



FIG. 101. Diagram of a toy motor. I, sectional view of the motor; II, the 

 armature enlarged; III, diagrammatic side view of commutator. 



clockwise direction about the upper one of these radial soft-iron 

 cores. When the current is flowing through this wire, the free 

 end a of the core is a south pole. It is, therefore, attracted to 

 the nearby north pole of the electromagnet and so causes the 

 armature to whirl in an anticlockwise direction. In a sixth of a 

 revolution of the armature, h and i are in contact with the metal 

 strips bringing in the current. They connect with the wire that 

 is similarly wound about the core whose free end is at b. But 

 the current goes through this wire in a reverse direction from 

 that which it had in the first coil; the free end b is, therefore, 

 a north pole, and is repelled by the adjacent north pole of the 



