. A text book of physics, for the use of students of science and engineering . Fig 931.—Magnetic field witharmature at rest. FIG. 932. -Magnetic field when currentflows in armature. in the armature, however, it produces a component of the magneticfield, perpendicular to that of the field magnets, and the resultantfield is as shown in Fig. 932. The brushes must now be placed at the ends of the diameterAB. The coil short circuited by the brush will then be movingparallel to the magnetic field, and the in it is zero, and excessive sparking will beavoided. The angle bywhich the line joining
. A text book of physics, for the use of students of science and engineering . Fig 931.—Magnetic field witharmature at rest. FIG. 932. -Magnetic field when currentflows in armature. in the armature, however, it produces a component of the magneticfield, perpendicular to that of the field magnets, and the resultantfield is as shown in Fig. 932. The brushes must now be placed at the ends of the diameterAB. The coil short circuited by the brush will then be movingparallel to the magnetic field, and the in it is zero, and excessive sparking will beavoided. The angle bywhich the line joiningthe brushes must be ad-vanced from AB to ABto stop sparking is calledthe lead of the brushes. To facilitate this adjust-ment the brushes are jcarried in brush holders(Fig. 933) attached to aframework which can berotated through any de-sired angle, the positionfor sparkless running beingfound by trial. Drum armature.—In the ring armature, the conductors lying outside the iron core cul the magnetic field as the armature rotates, bhose lying on the inside of the ring do no
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
