. Radiography and radio-therapeutics . at break; when the current appears at make it is known as reverse or inverse current. Coil construction is so arranged that aminimum of reverse current appears. The current which passes betweenthe terminals of the coil and through the tube when it is in the circuit shouldpass in one direction and is chiefly derived from the break. The greatdisadvantage of the induction coil as the means of transforming the low-tension current into one of high-tension lies in the difficulty of maintaininga unidirectional current; this difficulty is practically got rid of b
. Radiography and radio-therapeutics . at break; when the current appears at make it is known as reverse or inverse current. Coil construction is so arranged that aminimum of reverse current appears. The current which passes betweenthe terminals of the coil and through the tube when it is in the circuit shouldpass in one direction and is chiefly derived from the break. The greatdisadvantage of the induction coil as the means of transforming the low-tension current into one of high-tension lies in the difficulty of maintaininga unidirectional current; this difficulty is practically got rid of by 4 KADIOGEAPHY employing the high-tension transformer, for by its aid we get rid of theneed for an interrupter, and as reverse current is practically non-existentthe need for valve tubes is also obviated. There are many difficulties to be encountered in the working of chief of these lie in the manipulation of the X-ray bulb, for the vacuumof the tube is easily disturbed even in tubes which are exhausted to a high r^^^S. Condenser Fig. 1.—Diagram of arrangement of apparatus dealing particularly with the path of thecurrent from source to X-ray bulb. S, Secondary terminals, with X-ray tube in circuit. K, Commutator. M, N, Terminal screws for leads. X, X-ray tube. E, Metal disc or hammer. The current enters at tlie screw N, ascends the spring F, passes through the screw to G, then to thecommutator K, and through the primary back to the screw M, and from there to the battery. Thepassage of the current through the primary leads to two changes, (1) a momentary inverse currentis induced in the secondary coil; this is known as the current at make ; (2) the core is magnetisedand attracts the metal disc E on the spring F ; as a result the current is interrupted in its flow tothe primary. When the current in the primary is checked, the core becomes demagnetised, so that E fallsback, and the current is at once re-established. These alternations go on as long as the currenti
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