. Practical electricity in medicine and surgery. hollow conductor inclosing within itselfanother conductor, the two being separated by air or other * In the ease in which we have a medium other than air between the plates of the apparatusreferred to we have to write for the capacity C= E K being the specific inductive capacity, the remaining letters as before. 2 18 PRACTICAL ELECTRICITY IN MEDICINE AND SURGERY. dielectric medium, is called a condenser. Condensers of thisform have a very limited range of usefulness in practice becausetheir capacity is small; but standards are made in this way,
. Practical electricity in medicine and surgery. hollow conductor inclosing within itselfanother conductor, the two being separated by air or other * In the ease in which we have a medium other than air between the plates of the apparatusreferred to we have to write for the capacity C= E K being the specific inductive capacity, the remaining letters as before. 2 18 PRACTICAL ELECTRICITY IN MEDICINE AND SURGERY. dielectric medium, is called a condenser. Condensers of thisform have a very limited range of usefulness in practice becausetheir capacity is small; but standards are made in this way, andthe most accurate form of instrument is that of a sphere sus-pended within a concentric spherical shell. The capacity ofsuch condensers can be calculated at once when their dimensionsare known, and others, of forms rendering calculation impossible,but more convenient for general work, can be compared withthese and standardized. In the construction of condensers it is usual to employ alarge number of plates and to separate them by very small. Fig. 11.—Condenser. intervals. Generally, plates of tin-foil are used, these beingseparated by very thin sheets of prepared paper or mica, andseveral hundred of them placed together in a box. In this waythe capacity can be made as great as we please. Leyden Jars.—But the best-known type of condenser is theso-called Leyden jar (Figs. 12 and 13), which consists simplyof a glass jar covered inside and outside, except near the neck,with tin-foil. On top of the jar is a brass knob in metalliccommunication with the inside coating, but insulated from theoutside metal by means of a wooden stopper, through which theknob passes. Such a condenser, when made with thin glass,may have a very great capacity, and is altogether a convenient LEYDEN JARS. 19 form for general work in electricity. There is danger, however,that, when the glass is very thin, it may be ruptured by thepassage of a spark between the coatings, if they should be elec-trified to
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectelectri, bookyear1890
