Identifier: manualofxraytech1917chri (find matches)
Title: A manual of X-ray technic
Year: 1917 (1910s)
Authors: Christie, Arthur Carlisle, 1879-
Subjects: Radiography, Medical Diagnosis, Radioscopic X-rays Bones Gastrointestinal system Radiography Bone Neoplasms Gastrointestinal Diseases
Publisher: Philadelphia London : Lippincott
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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tion of tubes, besides making it diffi-cult or impossible to obtain good pictures. For thesereasons and because of its added efficiency, the typeof apparatus known as a transformer is at present themost satisfactory for exciting the Rontgen-ray tube. The transformer consists essentially of a primaryand a secondary coil, both surrounding a continuoussoft iron core. The principle is exactly the same as inthe induction coil. With the latter, however, aninterrupter must be used, while in the former an alter-nating current is utilized and the interruptions aresupplied directly from the dynamo. The voltage ofthe secondary current depends upon the proportionbetween the number of turns of wire in the secondaryto the number of turns in the primary. If, for in-stance, the secondary coil has twice as many turns 4 , 39 40 A MANUAL OF X-RAY TECHNIC as the primary then its voltage will be twice as greatas that of the primary. It should be rememberedthat the amperage undergoes opposite variations at
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Fig. 16.—Ring type of transformer. the same time. The transformer is a step-up or step-down transformer, depending upon whether thesecondary has a greater or less number of turns thanthe primary. For Rontgen-ray work the step-up EXCITING THE RONTGEN-RAY TUBE 41 transformer is necessary. The ring type of transfor-mer is illustrated in Fig. 16, showing the primary andsecondary coils surrounding a ring-shaped core ofiron. The transformer may be of the shell or jackettype, in which the primary and secondary coils aresurrounded by laminated masses of iron, which, froman electrical standpoint, constitute the core. The efficiency of the transformer is very high^being about 97 per cent, of the energy of the primary.The current furnished to the primary must be analternating one. If only a direct current is availableit must be changed to an alternating one by a motorgenerator. Operating the generator necessitates aconsiderable loss of energy, from 30 per cent, to 50per cent, being lost in thi

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