David Salomons

“ Any pressure of the current lost in a lamp produces a desired result. Since this is not so for the mains, the system must be constructed in such a manner that, except where practical results are needed, as little loss as possible shall occur in conducting the current from point to point,—which is effected by making the mains as large as possible. The size of the mains is limited only by the consideration of their cost. To sum this up, the whole pressure of the current may be regarded as being lost in passing through the lamps, motors, and other apparatus in a well-designed installation. ”

“ The engines employed are usually steam or gas, and both are so familiar to every one that to describe them is unnecessary. The apparatus which is revolved by the engine and termed the dynamo, in which the current is actually or, more strictly speaking, the apparatus in which the power derived from the engine is converted into electrical energy, will claim our attention after a brief reference to batteries. ”

“ In the arc lamp the current passes through two carbon rods, which are separated from each other by a very short distance. In order that the current shall leap this interval, the rods are made to touch each other, and then they are separated: a flame, consisting of heated gases, passes between these carhon rods, which flame must not be mistaken for visible electricity. The powerful light is produced by the intense heat to which the ends of the rods are raised. Suitable apparatus is connected with these carbons, in order that they may be fed as they burn away. ”

“ A piece of soft iron, wound round and round with wire which has a current passing through it, becomes a powerful magnet; and the iron is then said to be excited. When the electro-magnet of the dynamo is excited, the armature is in an extremely powerful magnetic field; which means that it is strongly under magnetic influence. If the spindle is revolved under these conditions and the wires leading from the brushes are connected so as to form a closed circuit, it will be found that the power required to turn the spindle increases as the speed is raised. ”

“ The larger the section of a wire, the less resistance does it offer to the passage of the current. Therefore one wire double the diameter of another will offer four times less resistance. On the other hand, if the current passing through any wire is doubled, the loss of pressure in travelling a given distance will be four times greater than before; three times the current, nine times: i.e., the waste increases as the square of the current. In electric lighting, the waste invariably consists in producing heat at places in the circuit where heat is not required ”

“ If it is required to turn a lathe or other machine by power at any given place, it will simply be necessary to convey to that place two wires to conduct the current, and then attach a motor. Although heavy, a motor is compact, and a man can, without difficulty, move from place to place, on a properly-designed truck, such a machine up to the size of say ten horse-power. ”

“ Although there is a variety of ways of producing electricity, from the rubbing of a piece of sealing-wax on the coat-sleeve to the vast engines employed at large central lighting-stations, yet here we will consider only such methods of producing the force as are in practical use on a moderate scale. The current for electric lighting may be obtained either from chemical batteries or from machines termed dynamos. ”

“ The development of the science in its application to the practical needs of human life may be considered to date from the time of Faraday, whose career ended about the middle of the present century. In the past forty years electrical science has advanced in a degree probably unequalled by the progress of any other science since the commencement of the world’s history. ”

“ In order that the untrained mind may realize natural laws and phenomena which are either unknown or unfamiliar to it, the necessity arises to introduce comparisons between them and the phenomena which are within its knowledge. ”

“ The alternating current may be regarded as a fluid in which a wave proceeds first in one direction and then in the other, seesaw fashion; and in practice these changes of direction take place as frequently as from fifty to two hundred times per second. Instruments employed for continuous currents may contain iron and permanent magnets, but for the alternating currents the latter must be completely absent, and any iron employed in the construction of the instruments must be very soft and much subdivided, or it will become extremely hot. ”

“ It would be possible to speculate to an unlimited degree as to the future of science, but experience shows that the knowledge of to-day is as nothing compared with that of to-morrow. A few new facts often upset pet theories. ”

“ The transmission of messages across the ocean dates so recently as to be within the memory of those who can look back some thirty years, The electric light can only be considered to have entered the practical stage since 1880; and, though the advances during the last few years have been great, we know that greater achievements are in store for the present and future generations. ”

“ Apart from the rapidity and ease with which motive power may be installed wherever it may be desired, there are also eliminated the dangers, disadvantages, and complications which exist more or less in connection with the forms of motive power hitherto employed. ”

“ Each plate is insulated from the next and from the spindle. By insulation is meant that some substance through which the electricity will not pass is placed between plate and plate, and between plates and spindlee. Upon this commutator rest two brushes, to which are attached the wires that lead to any point where electrical energy is required. Every plate in the commutator has a wire joined to it, the other end of the wire being in connection at certain points of the armature-coil. ”

“ To avoid the possibility of such an accident, the current is made to pass in its course, at suitable points, through short pieces of metal far more fusible in nature than the material of which the conductors are made. ”

“ The resistance of the one-hundred-volt sixteen-candle-power glow- lamp most commonly in use at the present time is about one hundred and seventy times greater than that of the mains and branches leading to it. ”