. Radiography and radio-therapeutics . o that the distance between the platinumtips can readily be adjusted. The current is passed from the positive pole of battery or mains intothe adjusting screw d, thence through the platinum contacts B, the primarywinding PP, thence back to the negative pole Tg. The circuit being com-pleted, the core T becomes magnetised, the iron hammer H is attracted,and the platinum contacts are pulled apart, thus breaking the circuit. The core thereby becoming demagnetised, the platinum contacts are ^ The most common form of sectional winding is illustrated in the acco
. Radiography and radio-therapeutics . o that the distance between the platinumtips can readily be adjusted. The current is passed from the positive pole of battery or mains intothe adjusting screw d, thence through the platinum contacts B, the primarywinding PP, thence back to the negative pole Tg. The circuit being com-pleted, the core T becomes magnetised, the iron hammer H is attracted,and the platinum contacts are pulled apart, thus breaking the circuit. The core thereby becoming demagnetised, the platinum contacts are ^ The most common form of sectional winding is illustrated in the accompanying figure,the ends of the sections being joined together alternately at the inside and the each section is a layer of some insulating medium, usually waxed or varnishedpaper, the thickness of which must be sufficient to stand the tension between the inner andouter ed^es of the sections, a pair of sections joined together in the inside having consider-able difference of tension at their outer edges and vice Fio. 7.—Diagram of sectional winding of secondary coil. (R. S. Wright, ) INDUCTION COIL—THE CONDENSER 19 pulled together again by means of the brass spring, and contact is againmade, and the core T again magnetised, and so on. C is the condenser,the thin hnes representing leaves of tin-foil, the thick ones insulating parti-tions of waxed or varnished paper. When the contact at B is broken, the current passes into one side of thecondenser at C, and by providing this alternative path the necessary sparkingat B is greatly reduced, and, what is of much greater consequence, the sudden-ness of the break, and therefore the speed at which the core becomes de-magnetised, is greatly increased. The electric motive force or spark leng-th increases with thenumber of turns of the secondary winding. By choosing the number of turns it is possible to transform a primarycurrent of 200 volts to 50,000 or 100,000, but the number of amperes isreduced in
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