. The principles of physics. r cars in the same would be possible for one car of an electric system, inrunning down a steep hill, to have its mechanical energyabsorbed by its motor acting as a dynamo (and thus servingas a brake to retard its motion), and thus to draw another carof the same system up a hill miles distant. 534. The action of the dynamo-motor. — This may be under-stood by referring to Fig. 464, and imagining a generatorto replace the external resistance R. Suppose the currentfrom the generator entersat the brushes and flowsin the loop in the direc-tion of the arrows ;
. The principles of physics. r cars in the same would be possible for one car of an electric system, inrunning down a steep hill, to have its mechanical energyabsorbed by its motor acting as a dynamo (and thus servingas a brake to retard its motion), and thus to draw another carof the same system up a hill miles distant. 534. The action of the dynamo-motor. — This may be under-stood by referring to Fig. 464, and imagining a generatorto replace the external resistance R. Suppose the currentfrom the generator entersat the brushes and flowsin the loop in the direc-tion of the arrows ; thenthe upper face of the loopwill have S polarity andthe under face N by the mutual actionbetween this field andthat of the magnet N S, a rotation of the loop will take placeclockwise till it comes into a vertical position. When itreaches this position, however, the brushes are so arrangedwith reference to the commutator segments that the currentin the loop — and hence its polarity — is reversed. Even if. 574 ETHER DYNAMICS. there were only one loop its inertia would be tocarry it by this critical position, and the loop would continueto rotate in the attempt again to bring its field parallel to thatof ]Sr S ; but as a matter of fact the other loops in thearmature are never in the critical position at the same timeas the one considered, and those on each side of it conspireto produce a continuous rotation in the same direction. If the armature contain a soft iron core, as is usually thecase, the intensity of the field will be much greater and themechanical effect correspondingly increased. Eig. 466 represents a modern form of motor weighing onlytwo or three pounds, and capable, when worked with four or five Bunsen cells, ofoperating a sewingmachine or running asmall saw. It consistsof a movable coil with-JLj-^-^^S^^^^^^^^W ill ^ fixed coil. The Irtm ^ wires of each coil are wound on an ironj,jg ^gg frame-work, the two opposite edges of theiron be
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
