. Electricity in diseases of the eye, ear, nose and throat . Figure 22l^. In Figure 22, any amount of oiiniic resistancedesired can be obtained by withdrawing one or moreplugs; for example, 40, 1, 2, 3—43 ohms. The boxmay be used to determine the resistance of a patientby substituting the patient for the box. Suppose,with the patient in the circuit, the meter shows 5 of current. Substitute the box in the circuit, turnon the same voltage as previously and regulate theresistance in the box so that the meter reads 5 m. resistance will be the same as that of the pat-ient. THE INDUCED O
. Electricity in diseases of the eye, ear, nose and throat . Figure 22l^. In Figure 22, any amount of oiiniic resistancedesired can be obtained by withdrawing one or moreplugs; for example, 40, 1, 2, 3—43 ohms. The boxmay be used to determine the resistance of a patientby substituting the patient for the box. Suppose,with the patient in the circuit, the meter shows 5 of current. Substitute the box in the circuit, turnon the same voltage as previously and regulate theresistance in the box so that the meter reads 5 m. resistance will be the same as that of the pat-ient. THE INDUCED OE FARADIC CURRENT. This is the current produced by the small coil ofthe usual medical wall plate. Faraday discovered, in 1831, that by moving amagnet near a closed circuit, an induced currentwould be produced in it; and also, later, that thisinduced current could be produced in a closed cir- THE INDUCED CUEKENT. 31 cuit when a current in a neighboring closed circuitwas varied in strength, by any Figure Fig. 23. If the intensity of the current in one coil A.,called the primary does not vary in strength, it willnot excite an induced current in the coil B, near intensity may be varied either by approachingor withdrawing either coil from the other or by mak-ing and breaking the circuit of the primary coil means of the interrupter below C. The closing and opening of the interruptermakes and breaks the current in A., producing mag-netic lines of force, as shown by the arrowed ringswhich cut the coil B. at right angles and excite in itan induced current, that gives a to and fro move-ment to the index of the nieter. When the circuit is open, the gap is completedby air conduction, which has so high a resistance asto prevent the flow of the current, unless this is ofvery high intensity. 32 • PHYSICS OF ELECTRICITY. The Faraday Ring is an induction coil and24. the first transformer ever constructed. See Figure
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjecteye, bookyear1912
