. Practical electricity in medicine and surgery. ron or steel in the helix, and it is much greater for soft ironthan for hard iron or steel. When a magnetic body has beenmagnetized so strongly that a great increase in magnetic forceproduces only a slight increase in its magnetism, the body issaid to be saturated. Galvanometers.—We have learned from Oersteds experi-ments that a current of electricity in a wire tends in general todeflect magnets near it from their normal position to one at right 66 PRACTICAL ELECTRICITY IN MEDICINE AND SURGERY. angles to the current, and the greater the current
. Practical electricity in medicine and surgery. ron or steel in the helix, and it is much greater for soft ironthan for hard iron or steel. When a magnetic body has beenmagnetized so strongly that a great increase in magnetic forceproduces only a slight increase in its magnetism, the body issaid to be saturated. Galvanometers.—We have learned from Oersteds experi-ments that a current of electricity in a wire tends in general todeflect magnets near it from their normal position to one at right 66 PRACTICAL ELECTRICITY IN MEDICINE AND SURGERY. angles to the current, and the greater the current the greater theangular deflection produced. We could, therefore, construct onthis principle an instrument capahle of measuring the relativeintensity of different currents. Instruments of this kind are nowin very general use, and are called galvanometers (Fig. 55). In its most general form a galvanometer is simply a circu-lar coil of wire, fixed by means of a suitable framework in anupright position, and having suspended at its centre a magnet. Fig. 55.—Galvanometer. (Thomson.) which can rotate about a vertical axis. The magnet itself isgenerally a small piece of steel strongly magnetized and pro-vided with a pointer and a scale so that its position may beaccurately known. A small magnet must be used, so that itspoles, in all positions of the needle, may be regarded as sensiblyat the centre of the coil, for reasons to be afterward explained,and a pointer is necessary to magnify the angular rotation ofthe needle. GALVANOMETERS. 67 In the galvanometer the aim is to so arrange the wires thatthe greatest effect can be secured at a given point with theminimum amount of wire, and to secure this the wires are al-ways arranged in the form of a circle. Generally there aremany turns of wire forming the coil of the galvanometer, sothat the magnetic force may be great. But the number of turnsof wire as well as the size of conductor employed depend uponthe currents which are to be measur
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectelectri, bookyear1890
