The Electric Light in Its Practical Application

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E. & F. N. Spon, 1879 - Electric lighting - 240 pages
 

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Page 86 - ... cores. It will be seen that this constitutes a double machine, each series of coils, with its commutator, being capable of .use quite independently of the other,; but in practice, the electrical connections are so made that the currents generated in the two series of armature coils pass through the field-magnet coils, and are joined in one external circuit. This form of armature also presents considerable uncovered surface of iron to the cooling effect of the air, but...
Page 27 - FIG. 46. the current circulating through m renders it magnetic and attracts the armature, a, thus separating the electrodes, when, on the weakening of the current, the elasticity of the rod, b, again restores the contact. During the movement of the negative electrode, since it is caused to occur many times...
Page 139 - A 2 , the small Brush machine, it will be noticed that two separate values are given for the resistance of the machine. These correspond to different connections, viz., the resistance, 1-239 ohms, being the connection at the commutator for low resistance, the double conducting wires being coupled in multiple arc, while 5-044 ohms represent the resistance when the sections of the double conductor are coupled at the commutator in series. Referring to Table III, the numbers given in the column headed...
Page 28 - In order to prevent a break from occurring in the circuit when the electrodes are consumed, a button, u, is attached to the upper extremity of the rod, R, at such a distance that when the carbons are consumed as much as is deemed desirable, it comes into contact with a tripping lever, T, which then allows two conducting plugs attached to the bar, v, to fall into their respective mercury cups, attached respectively to the positive and negative bind-posts by a direct wire.
Page 155 - Where it is desired to produce light, the external resistance is generally that of an arc formed between two carbon electrodes ; the resistance of the arc is therefore an important factor in determining the efficiency. To realize the greatest economy, the resistance of the arc should be low, but nevertheless should constitute the greater part of the entire circuit resistance. In some of our measurements the resistance of the arc was surprisingly low, being in one instance .54 ohm., and in another...
Page 132 - T079 the assumed normal value of the electro-motive force of a Daniell's cell, and R the resistances in the circuit with the battery, gives at once the current. In comparison with the total resistances of the circuit, the internal resistance of the battery was so small as to be neglected. The results obtained were as follows : The weber currents, as calculated from the above data, are given in Table IV.
Page 130 - ... wires were used throughout these experiments. Being of heavy copper, their resistance was low, viz.: about '016 ohm. Having thus obtained the circuit resistances, we proceeded to determine the value of the current. Here the choice of a number of methods presented itself. We selected two methods, one based on the production of heat in a circuit of known resistance, and the other upon the comparison of a definite proportion of the current with that of a Daniell's battery. In the application of...
Page 139 - Brush machines, if the measurement of the smaller of these machines be taken at the higher speed. The amount of light produced, however, is not the same in these two instances, being considerably greater in the case of the larger machine. The explanation of this apparent anomaly is undoubtedly to be found in the different resistances of the arcs in the two cases. In the large Brush machine the carbons are nearer together than when the small machine is used. This suggests the very plausible explanation,...
Page 26 - A flexible bar, b, of metal is firmly attached at one of its ends to a pillar, p, and bears at its other end an iron armature, a, placed opposite the adjustable pole-piece of the electro-magnet, m. A metal collar, c, supports the negative electrode, the positive electrode being supported by an arm,/., attached to the pillar...
Page 146 - ... maintain the speed and other conditions normal. One of the most important conditions necessary to insure correct results was the relative position of the carbon points. Great care was taken that the axes of the two sticks or pencils of carbon were in the same line, so that the light produced should be projected equally in all directions. Were the axes of the carbon pencils not in the same line, a much greater quantity of light would be projected in one direction, and the result of calculation...

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