Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . ng upon two ad- FiS- 324.—Eight-Coil Gramme King Directj. i hi xi Current Armature. jacent bars will thus short-circuit each coil for an instant as it passes from pole topole, and this short-circuiting should occur when there iszero E. M. F. in the coil, or at that instant when the mag-netic lines threading through it are a maximum, which will be when its plane is at rightangles to the lines of forcethreading through the ironring. The act of commuta-tion is further described in«|j 33
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . ng upon two ad- FiS- 324.—Eight-Coil Gramme King Directj. i hi xi Current Armature. jacent bars will thus short-circuit each coil for an instant as it passes from pole topole, and this short-circuiting should occur when there iszero E. M. F. in the coil, or at that instant when the mag-netic lines threading through it are a maximum, which will be when its plane is at rightangles to the lines of forcethreading through the ironring. The act of commuta-tion is further described in«|j 338 and Fig. 351. 327. Induced E. M. a Ring Armature.—Theupper and lower coils in theright-hand half of the ringFig. 325.—Multi-Coil Gramme Ring armature, Fig. 324, will haveDirect Current Armature. about the same E. M. F. in- Smooth core pattern. duced in themj gay 2 volts each, while the two coils between them will have a higherE. M. F. at the same instant, say 4 volts each, since theyoccupy nearly the position of the maximum rate of changeof the lines threading through them. The total E. M. 348 PRACTICAL ELECTRICITY. of this half of the ring, since these four coils are in series,will therefore be 2 + 4 + 4 + 2 or 12 volts, and sincesimilar induction takes place in the other half of the ring atthe same instant, there will be a total of 12 volts induced init. The windings of the two halves being in parallel, theE. M. F. at the brushes will also be 12 volts, just as thougheach half represented a cell of 12 volts E. M. F. and the two cells were placed in parallel. Thecurrent in the external circuitwill be the sum of the currents ineach half of the windings. If itis 10 amperes, 5 amperes will £ Volts 2 Volts <r •» 1 \ V)
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyo, bookyear1901
