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so the induced current is alternating--changing its direction of flow at regular intervals--whenever the two halves of each loop reverse their direction of cutting lines of force. When an armature loop is at the point of changing the direction of the flow of the induced current in itself it is scarcely cutting any lines of force, consequently it is inducing no current. As the loop revolves it gradually cuts more and more lines of force until it reaches the densest portion and from the point gradually cuts fewer and fewer lines of force until it is at the point of again changing its direction; thence it gradually reaches its maximum, decreases to zero again, and changes its direction once more. Each complete operation is called a CYCLE.
    Figure 20 shows a drawing of a small A.C. generator the field coils the field coils may be supplied by current delivered by a battery or a D.C. generator which we are now going to study.

Fig. 22


D.C. GENERATORS
    Before taking up the study of the production of direct current by mechanical means, it will be well to remember that all Radio receivers use direct current.
    In modern receivers, direct current is obtained by “rectifying” (making over) alternating current into D.C. current. The only place in a Radio receiver where alternating current can be used as it comes from the light socket is in the vacuum tube filament circuits where electricity is used only for heating purposes. It is, therefore, essential that a Radio-Trician understand the principles of direct current and its production from alternating current, and especially those methods of producing D.C. (by D.C. generators) as used in all broadcasting transmitters, all

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Webpage©1997, Nostalgia Air
Transcriber  Jennifer Ellis