. Practical electricity in medicine and surgery. B, then whenthe pointer is exactly over A the deflection should be calledJ.; if nearer to A than to B, it should be called i A\\ if ex-actly midway between A and B, it should be called J.^; andlastly, if the pointer is nearer to B than to A, then the deflectionshould be called lA%; thus, for example, if B and A (Figs. 62,63, 64, 65) were the 57° and 58° division marks respectively * Hand-book Electrical Testing, Kempe, p. 41. 78 PRACTICAL ELECTRICITY IN MEDICINE AND SURGERY. on the scale, then, in case 1 the deflection would be taken as57°, in c
. Practical electricity in medicine and surgery. B, then whenthe pointer is exactly over A the deflection should be calledJ.; if nearer to A than to B, it should be called i A\\ if ex-actly midway between A and B, it should be called J.^; andlastly, if the pointer is nearer to B than to A, then the deflectionshould be called lA%; thus, for example, if B and A (Figs. 62,63, 64, 65) were the 57° and 58° division marks respectively * Hand-book Electrical Testing, Kempe, p. 41. 78 PRACTICAL ELECTRICITY IN MEDICINE AND SURGERY. on the scale, then, in case 1 the deflection would be taken as57°, in case 2 the deflection would be taken as 57£°, and again,in cases 3 and i, the deflections would be taken as 57^° and57-f ° respectively. By keeping to these instructions, then, we can be certainof the magnitude of a deflection within \ of a division ordegree. Dynamometers.—According to Amperes laws of the mutualaction of currents (page 63), we know that currents which areparallel and in the same direction attract each other, and we can. Fig. 66.—Dynamometer. prove that this attraction is greater the greater the currents andthe closer together the conductors carrying them. This is, then,another phenomenon which we could make use of for the meas-urement of currents. Instruments constructed on this principle,, depending for their action on the mutual force existing be-tween wires conveying electric currents, are called dynamometers(Fig. 66). Such instruments possess this important advantageover galvanometers: they are not subject to the errors resultingfrom the variable magnetization of directing magnets, etc., andthe changes in the earths field. DYNAMOMETERS. 79 Dynamometers consist essentially of two coils of wire,placed at right angles to each other, one of which is movable andone fixed (Figs. 67, 68, and 69). The movable coil, A, is gen-erally quite small compared with the fixed coil, B, and is sus-pended within this by means of two very thin and parallel wires,W
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectelectri, bookyear1890
