. Elementary and dental radiography / by Howard Riley Raper . and low in amperage. It differs from the transformerin mechanical construction, and also in that the primary currentmust be an interrupted current, and the secondary, induced current is Fig. 12. A static machine. practically a uni-directional one. It will be recalled that the primary andsecondary currents of the transformer are both alternating. Let us trace a current of electricity from theInstallation. mains through an induction coil and auxiliary appli- ance leading to it. (Fig. 17.)Wiring from the mains to the coil should always
. Elementary and dental radiography / by Howard Riley Raper . and low in amperage. It differs from the transformerin mechanical construction, and also in that the primary currentmust be an interrupted current, and the secondary, induced current is Fig. 12. A static machine. practically a uni-directional one. It will be recalled that the primary andsecondary currents of the transformer are both alternating. Let us trace a current of electricity from theInstallation. mains through an induction coil and auxiliary appli- ance leading to it. (Fig. 17.)Wiring from the mains to the coil should always be done by a com-petent electrician. A wire of a given size will carry only a certain am-perage without heating. If this amperage be exceeded greatly the wire i6 ELEMENTARY RADIOGRAPHY may become hot enough to set fire to surrounding building material of acombustible nature. There are, therefore, laws governing the size ofwires to be used to carry different amperages. Coils are rated by theirmanufacturers to consume a certain number of amperes, and wiring. Fig. 13. Induction or Ruhmkorff coil. should be done according to this rating. The amount of amperage neces-sary to operate a coil varies directly according to the size of the coil—the larger the coil the more amperes it takes. Assuming the coil to beof a medium large size, the lead wires used to connect it to the mainsshould be capable of carrying at least 30 amperes without heating. Bylead wires I mean the wires leading to the machine—not lead (themetal) wires. The wires are copper. X-RAY MAC MIXES 17 Somewhere near where the wires enter theTurn. building, and also at the coil itself, will be found fuses. (Fig. 18.) A fuse is a wire, an alloy oflead, of a given size, and fusing point, capable of carrying only a limitedamperage without melting. Thus, if more than 30 amperes be sentthrough a 30-ampere fuse, the wire is heated to its fusing point, it melts,the circuit is broken, and the flow of electricity is stopped. A f
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