. Practical electricity in medicine and surgery. ver, now manufactured which arecapable of driving small motors, and which have been foundquite satisfactory. In some cases the electric-light current is available, eitherfrom a central station or from some neighboring plant, and underthese circumstances motors may be supplied with current with-out any difficulty. It is altogether immaterial what particularsystem of electric distribution may be adopted at the station, sincemotors may be constructed in such a way that they can bejoined to any circuit whatever. But, it must be added, the motorwill
. Practical electricity in medicine and surgery. ver, now manufactured which arecapable of driving small motors, and which have been foundquite satisfactory. In some cases the electric-light current is available, eitherfrom a central station or from some neighboring plant, and underthese circumstances motors may be supplied with current with-out any difficulty. It is altogether immaterial what particularsystem of electric distribution may be adopted at the station, sincemotors may be constructed in such a way that they can bejoined to any circuit whatever. But, it must be added, the motorwill have to be built in accordance with the conditions underwhich it will be supplied with current. Resistance Coils, Rheostats, etc.—Resistance coils, sometimescalled rheostats, rheotomes, etc., are made in great variety ofform, according to the special purposes for which they are in- RESISTANCE COILS, RHEOSTATS, ETC. 131 tended, but they are nearly always constructed so that theresistance in circuit may be varied at will between certain Fig. 118.—Resistance Coils. In some forms this can be done by a continuous variation, butusually the resistance must be changed by steps; that is, the T (DQOC Fig. 119. resistance must be changed one or more ohms at a time. Aresistance box of the latter kind is that shown in Fig. 118. It 132 PRACTICAL ELECTRICITY IN MEDICINE AND SURGERY. consists of a rectangular box with a hard-rubber top, havinginside a number of spools of German-silver wire connectedthrough the top with brass pieces of appropriate shape. Thebrass pieces (^1 A) are of the form shown in Fig. 119; they areplaced close together, and contact from one to the other is madeby inserting plugs (B) into half-rounded cavities between them. .The coils of wire forming the various resistances are joined oneend to one block, and the other end to the next adjacent block,thus bridging across from one block to the other. In windingthe cods it is usual to double the wire—which is al
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectelectri, bookyear1890
