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The drum with the wire wound about it is called the "Armature."
In the practical machine used in electric lighting, the core of the armature is made of thin discs of soft sheet iron; these discs are prevented from touching the shaft by the interposition of insulating material, and have insulating material, arranged between them so as to prevent their touching each other, they are however so rigidly secured to the shaft as to be in no danger of becoming loose when the shaft is rapidly rotated. Fig. 5 shows a complete armature, with commutator attached ready to be placed in position in the generator.
When the parts of a generator are properly connected to each other, as well as to the outside lamp circuit, the current generated in the armature, is augmented by the presence of the iron core, which attracts the lines of force extending out from the field pieces, and so concentrates them as to cause the wire wound about it to cut through the
