Transportation on Land 



323 



point of support by fitting a spool into the hole of the wooden disk. 

 Close the upper opening of the spool with a piece of dented tin (see 

 diagram of cross section). 



Support the brushes (B, B) which conduct the electric current to 

 the commutator (C) on two spools (Sp) held in place by long nails. 



FIG. 102. A plan for the construction of an electric motor. 



See that the brushes, strips of copper sheeting, make good contact 

 with the wires from the battery. 



When you have completed the motor, set it up as shown in the 

 diagram with two batteries (page 333) of two cells each. The current 

 from a single battery of several cells may be passed first through the 

 armature, and then through the field coils which form what is called 

 the electromagnet. 



