Electrical discharge

“ It is probable that they are glow discharges which appear just before the difference of potential between the cloud and the earth becomes sufficiently great to give rise to a lightning flash.
320. The Electrical Discharge in Rarefied Gases.—If the air between the electrodes of an electrical machine be heated, it is found that the discharge takes place with greater facility and that the spark which can be obtained is longer than befuie. Similar phenomena appear if the air about the electrodes be rarefied by means of an air-pump. ”

“ The electrical discharge can accomplish all this, but the story of its activity is not yet told. It can not be told, for each year adds information in regard to these activities, for there are thousands of investigators at work. Another far-reaching manifestation is this: the rays can separate the air or a gas into its constituent particles, much as a strong electrical current separates water into oxygen and hydrogen. They can communicate electrical charges to these particles—positive and negative charges. ”

“ In discharging electrical jars, the electricity goes in the greatest quantity through the best conductors, and by the shortest passage. Thus if a chain and a wire be made to communicate at the same time with the outer coating of a jar, and be both presented to the knob of that jar, the greater part of the charge will pass by the wire, and very little by the chain, because the latter is a worse conductor than the former, on account of its discontinuation at every link. When the discharge is 29made by the chain only, sparks are seen at every link, which is a proof they are not in contact. ”

“ As soon as this circuit is provided, the opportunity is given to the iron to receive the oxygen. This it does, and in so doing develops electrical energy.
This energy is in the form of electric current which is then delivered by the battery on what is called the "discharge," and this current may be used for lighting lamps or for operating motors or other electrical devices.
The battery is said to be discharging as long as the iron is receiving oxygen from the nickel oxide. ”

“ In reality the advance was enormous; it gave a means for literally bottling up electricity in quantities previously unthought of. The prime conductor of an electrical machine could not retain any considerable quantity of electricity for the reason that, a certain small intensity of electrification having been reached, [Pg 247] the addition operated to upset the balance, so to speak, and the electricity escaped by a sudden (disruptive) discharge, or spark, or by the brush discharge already alluded to. ”

“ The current may be regulated by altering the distance between the plates or by varying the strength of the solution. As the discharge progresses, the voltage will gradually decrease and it should be frequently read at the battery terminals. When it shows a sudden drop, the voltage of each cell should be read with a low reading voltmeter.
While the readings are being taken, the discharge rate should be kept constant and the discharge continued until the majority of the cells read 1.70 volts; those reading less should be noted. ”

“ Leyden jar, or of many other charged conductors, is oscillatory in
character. The direction of the currents rapidly changes, so that the
discharge is really an alternating current of excessively short total
duration. The discharge sends electro-magnetic waves through the ether,
which are exactly analogous to those of light but of too long period to
affect the eye.
Synonym--Surging Discharge.
[Transcriber's note: Marconi's transmission across the English channel
occurs in 1897, five years after the publication of this book.]
Fig. 132. DISCHARGER.
Discharger. ”

“ He reasoned out the subject, and concluded that the electric spark between metals, the electric arc between the carbons, and other luminous electric phenomena are secondary effects due to the heating and illumination of electric carriers; that the electric spark of the conductors of ordinary electrical machines is simply a transfer of incandescent particles of metal, which effect a kind of electric convection, known as the disruptive discharge ”

“ However extraordinary the results shown may appear, they are but trifling compared with those which are attainable by apparatus designed on these same principles. I have produced electrical discharges the actual path of which, from end to end, was probably more than one hundred feet long; but it would not be difficult to reach lengths one hundred times as great. I have produced electrical movements occurring at the rate of approximately one hundred thousand horse-power, but rates of one, five, or ten million horse-power are easily practicable. ”

“ That the electricity was apparently not analogous to voltaic electricity is evident, for the "usual shocks" only were produced, and nothing like the terrible sensation due to a voltaic battery, even when it has a tension so feeble as not to strike through the eighth of an inch of air.
341. It seems just possible that the air which was passing by the kite and string, being in an electrical state sufficient to produce the "usual shocks" only, could still, when the electricity was drawn off below, renew the charge, and so continue the current. ”

“ When the charge of electricity is removed from a charged body it is said to be discharged. Good conductors of electricity are instantaneously discharged if touched by the hand or by any conductor in contact with the ground, the charge thus finding a means of escaping to earth. A body that is not a good conductor may be readily discharged by passing it rapidly through the flame of a lamp or candle; for the flame instantly carries off the electricity and dissipates it in the air. ”

“ When the charges rush together they form a current which burns out the air in the gap and this gives rise to the spark, and as the heated gap between the two electrodes is a very good conductor the electric current surges forth and back with high frequency, perhaps a dozen times, before the air replaces that which has burned out. It is the inrushing air to fill the vacuum of the gap that makes the crackling noise which accompanies the discharge of the electric spark. ”

“ Fortunately for the future delivery of energy at great distances from its source, the means to avoid the limit just discussed are not difficult. Other experiments have shown that with a given voltage and distance between conductors the loss of energy from wire to wire decreases rapidly as their diameters increase. The electrical resistance of air, like that of any other substance, increases with the length of the circuit through it. The leakage described is a flow of electrical energy through the air from one wire to another of the same circuit. ”

“ Air charged with particles of damp is well known to be of all others the greatest enemy to electricity. It immediately attracts and dissipates all the electrical matter which is collected by the machine, which therefore worked faintly for a little while, till the damp was condensed on the conductor, and chiefly on the surface of the glass phial, and then ceased entirely. ”

“ When, therefore, disruptive discharge has once commenced at the root of a brush, the electric force which has been accumulating in the conductor attached to the rod, finds a more ready discharge there than elsewhere, and will at once follow the course marked out as it were for it, thus leaving the conductor in a partially discharged state, and the air about the end of the wire in a charged condition ”

“ It is open to the objection, however, that it in a measure legalizes the conveyance of electricity on conductors other than those designed for the purpose. In larger towns, with more than one power house and with car lines radiating from and circumscribing the business center, the attachment of conducting wires entails a ceaseless disturbance of the electrical equilibrium, curing the evil in spots and developing new danger points. ”

“ He has, in the first place, to make sure that, wherever the lightning can fall, it shall find an open and practically unobstructed path to traverse in its passage to the ground. He is quite sure that the electric discharge will confine itself to the track of a conductor, and will pass quietly and harmlessly along it, provided its dimensions are adequate to the task of transmission, and provided the inlets and outlets are sufficiently capacious for its unimpeded reception and escape. ”

“ In the arc discharge we get very large currents with comparatively small potential differences. We may get the arc discharge by taking a battery of cells large enough to give a potential difference of 60 to 80 volts, and connecting the cells with two carbon terminals, which are put in contact, so that a current of electricity flows round the circuit. If the terminals, while the current is on, are drawn apart, a bright discharge, which may carry a current of many amperes, passes from one to the other. ”

“ Experiments with charged electrics should always be made with caution, for though the discharge of a small phial through the body is seldom attended with bad consequences, yet that of a battery is always dangerous, and sometimes mortal. The operator should therefore be attentive, not only to the experiments he is about to perform, but also to the persons who may happen to be with him, forbidding them to come near any part of the apparatus. ”

“ The spark in these early experiments was usually supplied from the outer coats of a pair of oppositely-charged small Leyden jars, whose knobs sparked into each other; the idea being to ascertain all the conditions pertaining to the feeble residue of a lighting discharge which is liable to be conducted by telegraph wires to a distance, and there cause some damage to sensitive instruments not suitably protected from sudden electric jerks, whose laws of flow are quite different from those proper to steady currents. ”

“ When an alternating current is set up in the circuit containing the cathode, anode, and secondary of the transformer, the electronic discharge from the cathode closes the circuit and permits a continuous flow of electricity through it when the phase of the current is such than the anode is positively charged, while preventing any flow of current through the tube when the anode is negatively charged. ”

“ The Spark Discharge.—In practice the wire w is not actually used, but the air itself suddenly becomes a conductor and makes the connection. When the electric field at a point in the air exceeds a certain limiting strength, the air seems to break down and {85} suddenly become a conductor and remains one for a short time. This breaking down is accompanied by light and heat, and is known as the spark discharge or electric spark. ”

“ When they are gone, other uncharged particles take their place round the point, and since these cannot shield those next the point itself from the excessive electric tension, a new discharge takes place, after which the newly charged particles move off, and so on as long as the body remains electrified. ”

“ The conductor acts by induction upon the point, causing the negative electricity to stream from it against the conductor, which is thus neutralized almost as fast as it is charged. Flames and glowing embers act like points; they also rapidly discharge electricity.
The electricity escaping from a point or flame into the air renders the air self-repulsive. The consequence is that, when the hand is placed over a point mounted on the prime conductor of a machine in good action, a cold blast is distinctly felt. ”

“ Our knowledge seems rather to point to the substances upon which the charges are collected. The self-repellent nature of electricity compels it to manifest itself at the more prominent parts of the surface, the level being forsaken for the point. The tension of the charge, or its tendency to fly off, is proportionately increased. And if at a given moment the tension attains a certain intensity, the discharge follows, emanating from the surface which offers the greatest facilities for escape. ”

“ When the tension in the space between two conductors is considerable all the way between them, as in the case of two balls whose distance is not great compared with their radii, the discharge, when it occurs, usually takes the form of a spark, by which nearly the whole electrification is discharged at once. ”

“ In firing inflammable Substances, the Person who holds the Spoon in his Hand to receive the electrical Flashes, when the Finger of the electrified Person is brought near thereto, not only feels a tingling in his Hand, but even a slight Pain up to his Elbow. This is most perceptible in dry Weather, when the Electricity is very powerful.
There is a considerable Difficulty in firing Electrics per se, such as Turpentine, and Balsam Capivi, by the repulsive Power of Electricity ”

“ Were it not for the extremely high pressure of lightning discharges, their high frequency of oscillation would enable ordinary coils to be self-protecting against them. But a discharge of electricity can take place through the air or other insulating medium if its pressure be high enough. A pressure of 70,000 volts can strike across a gap in air of one inch, and lower pressures can strike across smaller distances. ”

“ In industrial accidents such nice adjustments are fortunately almost impossible, and shocks received from high-pressure currents, even of 25,000 volts, have not proved fatal because both the voltage and amperage have been greatly lessened through poor contacts and great resistance of clothing and dry skin, and also because the heart is not usually included in the circuit. ”