Brush (electricity)

“ In all such experiments as those described, the point of change from spark to brush is very much governed by the working state of the electrical machine and the size of the conductor connected with the discharging ball. If the machine be in strong action and the conductor large, so that much power is accumulated quickly for each discharge, then the interval is greater at which the sparks are replaced by brushes ”

“ The discharge by a brush is not to all the particles of air that are near the electrified conductor from which the brush issues; only those parts where the ramifications pass are electrified: the air in the central dark parts between them receives no charge, and, in fact, at the time of discharge, has its electric and inductive tension considerably lowered. For consider fig. ”

“ The brush and spark gradually pass into one another, Making a small ball positive by a good electrical machine with a large prime conductor, and approaching a large uninsulated discharging ball towards it, very beautiful variations from the spark to the brush may be obtained. ”

“ The brush form of disruptive discharge may be obtained not only in air and gases, but also in much denser media. I procured it in oil of turpentine from the end of a wire going through a glass tube into the fluid contained in a metal vessel. The brush was small and very difficult to obtain; the ramifications were simple, and stretched out from each other, diverging very much. The light was exceedingly feeble, a perfectly dark room being required for its observation. When a few solid particles, as of dust or silk, were in the liquid, the brush was produced with much greater facility. ”

“ If the rounded end of a metal rod, 0.15 of an inch in diameter, be made to give a good negative brush, the approach of a smaller end or a blunt point opposite to it will, at a certain distance, cause a diminution of the brush, and a glow will appear on the positive inducteous wire, accompanied by a current of air passing from it. Now, as the air is being charged both at the positive and negative surfaces, it seems a reasonable conclusion, that the charged portions meet somewhere in the interval, and there discharge to each other, without producing any luminous phenomena. ”

“ A series of rapid and successive reunions of the electricity with each bristle of the brush takes place, generating a current of cold air perceptible to the patient. I habitually use for this application an ordinary clothes-brush. If while in connection with the conductor any object (the knuckles will do) is brought sufficiently near to the patient for his contained electricity to overcome the resistance of the intervening stratum of air, he is “discharged” with a spark. This is Franklinization by sparks, and is accompanied by a certain slight amount of “shock.” ”

“ It is curious to observe the relation of glow, brush, and spark to each other, as produced by positive or negative surfaces; thus, beginning with spark discharge, it passes into brush much sooner when the surface at which the discharge commences (1484.) is negative, than it does when positive; but proceeding onwards in the order of change, we find that the positive brush passes into glow long before the negative brush does. ”

“ To sum up these considerations respecting the character and condition of the brush, I may state that it is a spark to air; a diffusion of electric force to matter, not by conduction, but disruptive discharge, a dilute spark which, passing to very badly conducting matter, frequently discharges but a small portion of the power stored up in the conductor; for as the air charged reacts on the conductor, whilst the conductor, by loss of electricity, sinks in its force (1435.) ”

“ How quickly a spoon inserted into a hot cup of tea becomes uncomfortably hot, though the hand can be held very close to the liquid without feeling more than a gentle warmth. And we all have noticed that the very least air-gap in an electric circuit effectively breaks a current capable of traversing miles of wire. If the current is so intense that it insists on passing the gap, it leaps across with a report, making a spark that is at once intensely bright and hot. Metal wires are to electricity what speaking tubes are to sound; they are as it were electrical tubes through the air and ether. ”

“ It is, therefore, evident that, when a ball is discharging electricity in the form of brushes, the brushes are far more numerous, and each contains or carries off far less electric force when the electricity so discharged is negative, than when it is positive. ”

“ He had never spoken more truly than when he told Yvonne that he felt "sort of responsible." Cecily, in this condition, stabbed his conscience. "Oh, good Lord!" he moaned mentally. "I bet I did this! I started it, anyhow, I know that. And she's taken all my advice and then gone to the other extreme!"
Yvonne's dressing room was a cubbyhole containing a table messy with cosmetics, a huge mirror framed in electricity, two kitchen chairs, and an assortment of gowns that peeped from behind a sheet stretched across one corner. ”

“ In the arc-lamp the electric circuit is broken at the point where light is required. In glow or incandescent lamps the current is only hindered by the interposition of a bad conductor of electricity, which must also be incombustible. Just as a current of water flows in less volume as the bore of a pipe is reduced, and requires that greater pressure shall be exerted to force a constant amount through the pipe, so is an electric current choked by its conductor being reduced in size or altered in nature. ”

“ If a piece of metal be presented to an over-charged prime conductor, the fluid passes with violence from the one to the other; an electric spark, having the appearance of fire, is seen flashing between them, and a snapping noise, like the cracking of a whip, is heard. If this piece of metal be insulated, the prime conductor will be only partially discharged, that is, the redundant electricity will be divided between it and the piece of metal, nearly in proportion to their surfaces. ”

“ However, with incomparably higher frequencies, which we may yet find means to produce efficiently, and provided that electric impulses of such high frequencies could be transmitted through a conductor, the electrical characteristics of the brush discharge would completely vanish—no spark would pass, no shock would be felt—yet we would still have to deal with an electric phenomenon, but in the broad, modern interpretation of the word. ”

“ Thus in paper-making machinery, where the band of paper passes at high speed over hot metal rolls, it may become electrified to the extent of sparking and igniting itself. To avoid this danger it is necessary to fix spiked combs, which draw off the charge as soon as generated. In all these cases the electricity produced by friction is only an inconvenient by-product of some other operation; but if we wish to produce electricity for experimental work we may use special appliances based on the principle of electrification by friction. ”

“ As the brushes stand still, two wires can be fastened to them, and thus the ampères of current of electricity, acted upon by the volts pressure, can be carried away to be used in the lamps, for you must remember that as long as the spool turns around it gathers more electricity while there is any magnetism for the wire on the spool to pass through. ”

“ Now, an electric fuse is what an electrical engineer might almost unconsciously carry about with him, it is so essential a part of his working tools, but it is a thing that a literary man or a press reporter could have no possible use for."
"Exactly, exactly. And it was no doubt, that bit of electric fuse that turned your thoughts to the one house in the neighbourhood lighted by electricity, and suggested to your mind the possibility of electrical engineers turning their talents to account in that direction. ”

“ The kind of electricity produced depends not only on the substance rubbed, but also on the material used as the rubber. For instance, we can give glass a negative charge by rubbing it with flannel, and sealing-wax becomes positively charged when rubbed with silk. ”

“ This experiment may be agreeably varied in the following manner.—A person may hold an excited tube of glass, within a foot and a half of a stick of sealing-wax, or any other electric negatively electrified, held by another person; a feather let fall between these differently excited electrics will leap from one to the other alternately, and the two persons will seem to drive a shuttlecock by the force of electricity. ”

“ Friction between a non-electric and an electric per se, will produce electrical fire; not by creating, but collecting it: for it is equally diffused in our walls, floors, earth, and the whole mass of common matter. Thus the whirling glass globe, during its friction against the cushion, draws fire from the cushion, the cushion is supplied from the frame of the machine, that from the floor on which it stands. Cut off the communication by thick glass or wax placed under the cushion, and no fire can be produced, because it cannot be collected. ”

“ Some improvement seems yet to be wanting at both extremities of the rod—at the upper extremity, to secure it against the accident of being melted, which renders it afterwards unfit to answer its original intention, viz. drawing off the electricity, or lightning, from the passing cloud, in a silent imperceptible manner, for it is only pointed conductors that possess this property—and at the lower extremity, to afford a more ready passage for the fluid into the surrounding earth. ”

“ Car after car leaves the highway and twists along a serpentine side-road, until its headlights are one with the light that blazes like noon in the clearing at the end. August Schultz has ever been a firm believer in electricity for outdoor use. ”

“ A wooden sphere covered with the thinnest layer of gold-beater's skin will at the same potential hold exactly the same quantity of electricity as if it were made of solid brass or lead or any other metal. Electricity at rest resides entirely on the outside of a metal conductor. We might reduce the thickness of a shell to any degree, and still the charge is not altered. ”

“ Under certain conditions the force of attraction may be sufficiently great and the distance sufficiently small to cause electricity to leap across the intervening space, and then we have the familiar phenomenon of an electric spark. ”

“ The particles of air along the path of the discharge are rendered incandescent by the heat produced by the passage of the electricity, and so the brilliant flash is produced. Just as a river winds about seeking the easiest course, so the electricity takes the path of least resistance, which probably is determined by the particles of dust in the air, and also by the density of the air, which becomes compressed in front, leaving less dense air and therefore an easier path on each side. ”

“ It is greater, for instance, in dense air than in rare air, and greater in glass than in air, but in every case, if the electromotive force be made great enough, the dielectric gives way and its insulating power is destroyed, so that a current of electricity takes place through it. It is for this reason that distributions of electricity for which the electric resultant force becomes anywhere infinite cannot exist in nature. ”

“ Just in the same way we might say that when we hold a poker with its point in the fire, heat flows along it towards our hand, although we know quite well that heat is not a fluid. In the experiment with the metal rod referred to above, the electricity flows away instantly, leaving the rod unelectrified; but if we arrange matters so that the electricity is renewed as fast as it flows away, then we get a continuous flow, or current. ”

“ If the tube be exhausted of air, a non electric lining in contact with the wire is not necessary; for in vacuo, the electrical fire will fly freely from the inner surface, without a non-electric conductor: but air resists its motion; for being itself an electric per se, it does not attract it, having already its quantity. ”

“ If you bring the sealing-wax near some light thing like down, this will cling to it for a moment, and then fly off again, as if it did not like the sealing-wax. It is the electricity which you have excited that does this.
A good deal of electricity can be made by rubbing glass. In the machine which is used in making electricity for experiments there is a large glass cylinder, which is turned round quickly against a leather rubber that has a preparation of mercury on it. ”

“ It is with such a rubber that the cylinder is most powerfully excited.
An ingenious friend has favoured us with the following explanation of the manner in which electrics are excited, which to us is more satisfactory than any other we have seen. “In order that electricity may be accumulated in greater quantity in one body than in the surrounding ones, it must be set in motion. ”

“ At a certain distance from the point the resultant force is not sufficient to break through the insulation of the air, so that the electric current is checked, and the electricity accumulates in the air round the point. ”

“ Fig. 117. Arc-Lighting Circuit.
A high voltage is necessary in order to cause the current to leap across the gap made by the separation of the electrodes
p. 166
The Incandescent System.—This method is entirely different from the arc system. It has been stated that certain metals conduct electricity with greater facility than others, and some have higher resistance than others. If a certain amount of electricity is forced through some metals, they will become heated. ”

“ There is no place of the earth or sea where the electric fire may not be collected, by making a communication between it and the rubber of an electric machine. Therefore, considering 121that the whole earth is moist, and that moisture is a conductor of electricity, and that every part of the earth must thus communicate with another, it is certain that the electric matter must diffuse itself as far as the moisture of the earth reaches ”