Static electricity

“ Static Electricity.—This is a term employed to define electricity produced by friction. It is properly employed in the sense of a static charge which shows itself by the attraction or repulsion between charged bodies. When static electricity is discharged, it causes more or less of a current, which shows itself by the passage of sparks or a brush discharge ”

“ It is vain to attempt to picture the marvels of the future. Progress, as Dean Swift observed, may be "too fast for endurance."
If the conductor is entirely insulated, so that no molecular movements can be communicated by it to contiguous bodies, all its particles become energized, and remain so as long as the conductor is attached to a source of electricity. In such a case an additional charge is required only when some of the original charge is taken away, escapes. This is Static electricity; the same as the other, but in theory differing in application. ”

“ The electric light is scarcely explainable upon any other hypothesis. The remaining conclusions may be left in abeyance, and without argument.
Science began with static electricity, so called, because its sources were more readily and easily discovered in the course of scientific accidents, as in the original discovery of the property of rubbed amber, etc., and the long course of investigations that were suggested by that antique, accidental discovery. What we know as the dynamic branch of the subject was created by the investigations of Faraday; induction was its mother. ”

“ It is evident, from the experiments, that bodies which conduct static electricity do not necessarily conduct galvanic electricity. The greater the E. M. F. of a current, the greater its power to overcome resistance. Some bodies, like dry wood, that readily conduct the high potential static electricity, make fairly good insulators for the low potential galvanic currents. ”

“ An electric current manifests itself by heating the wire or conductor, by causing a magnetic field around the conductor245 and by causing chemical changes in a liquid through which it may pass.
Note.—Statics is that branch of mechanics which treats of the forces which keep bodies at rest or in equilibrium. Dynamics treats of bodies in motion. Hence static electricity is electricity at rest. The earth’s great store of electricity is at rest or in equilibrium. ”

“ These experiments and many others show that there is no essential difference between the so-called static and dynamic electricity. In the one case it is developed upon a surface which has such a molecular character that it cannot be conducted away, every surface molecule being practically a little battery cell with one terminal free in the air, so that when a proper conductor approaches the surface it receives the electricity from millions of cells, and therefore becomes strongly electrified so that a spark may at once be drawn from it. ”

“ Three methods of generating electricity are in general use: static or frictional electricity is generated by "plate" or "static" machines; galvanic, generated by batteries based on Volta's discovery; and induced, or faradic, generated either by chemical or mechanical action. There is still another kind, thermo-electricity, that may be generated in a most simple manner. In 1821 Seebecle, of Berlin, discovered that when a circuit was formed of two wires of different metals, if there be a difference in temperature at the juncture of these two metals an electrical current will be established. ”

“ It has been stated that modern theory recognizes two classes of electricity, the Static and the Dynamic. The difference is, however, solely noticeable in operation. Of the dynamic class there can be no more common and striking example than the now almost universal electric light. Yet, with a sufficient expenditure of chemicals and electrodes, and a sufficient number of cells, electric lighting, either arc or incandescent, can be as effectively accomplished as with the current evolved by a powerful dynamo. ”

“ Nor do these wires either attract or repel light bodies in their vicinity, whereas static or ordinary electricity can be accumulated in insulated bodies to a great degree, and in that state of rest the tendency to escape is proportional to the quantity accumulated and the resistance it meets with. In ordinary electricity, the law of action is, that dissimilar electricities attract and similar electricities repel one another. ”

“ This curious conclusion of science, then, that the power from the power-station wire travels in the space around the wires led from the station, is one of the results of recent electrical studies, just as with light those studies begun by Maxwell and Hertz have led to the inevitable conclusion that the light of the candle, the light of a kerosene lamp, and the light of a gas burner are all in essence electrical phenomena, as are all forms of radiation in the ether (“Electricity During the Nineteenth Century,” Prof. Elihu Thomson, Washington, 1901) . ”

“ 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. ”

“ If, then, we define electric displacement as that change which takes place in a dielectric when it becomes the seat of electrostatic energy, and if, further, we suppose that the change, whatever it be mechanically, satisfies certain well-known laws, and that in consequence certain pressures and tensions exist in the dielectric, electrostatic problems can be solved without reference to a charge of electricity residing on the conductors. ”

“ Can we conduct from one place to another this peculiar state of things, this queer form of potential energy which we call electrification? It is clear, from the last experiments, that in order to do it we need something besides ebonite, which really acts like a closed stop-cock to the flow of electrification.
To keep electrification in one place we need an insulator; to get it from one place to another we need a conductor. Insulators are as important as conductors. ”

“ 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. ”

“ Each has a higher potential than the acid, but their potentials are not the same. This electrification tends to pass from the place of higher to the place of lower potential, and the conducting wire allows this transfer to take place. As the difference of potential is kept up by the continued chemical action, the current is continuous, and not simply instantaneous, as in discharges of frictional electricity. As heat is produced by the burning of coal, so electrification is produced by the chemical burning of zinc. ”

“ This transformer, as heretofore explained, does not change the voltage of the current, but simply transforms what was an alternating into a direct current. By alternating current we mean one that is made up of impulses of alternating polarity—first a positive and then a negative. The direct current is one whose impulses are all of one polarity. The direct current is required for all purposes where electrolysis (chemical decomposition by electricity, as of silver for silver-plating, etc.) is a part of the process. ”

“ There is an advantage in producing a high temperature in the filament of the incandescent lamp, but there is no advantage whatever in producing heat in the wires that carry the current to the lamp. On the contrary, there is an objection to it; not only does the generation of heat mean a dissipation of energy, that is, of something which costs money, but it may be a positive danger, since a conductor becoming red-hot may set fire to a building. ”

“ 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. ”

“ 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. ”

“ It will be observed that the segments of both discs, whilst passing each other on the horizontal diameter, are charged with electricity of the same sign, namely, positive on the left and negative on the right.
If we now inquire as to the true cause of electrification, we find that apart from the quite insignificant initial charge on A and B, it is simply the mechanical energy required to produce rotation against the opposing force of electrostatic attraction between the outer and inner segments. A has a positive, and a has a negative charge. ”

“ Thus, when a conductor having a sharp point is electrified, the theory, based on the hypothesis that it retains its charge, leads to the conclusion that as we approach the point the superficial density of the electricity increases without limit, so that at the point itself the surface-density, and therefore the resultant electrical force, would be infinite. If the air, or other surrounding dielectric, had an invincible insulating power, this result would actually occur ”

“ The current for power purposes is generated in a large stationary armature about ten feet in diameter and of the same depth as the revolving ring. The revolutions of the ring send out currents of alternating polarity, and each of the ten machines will furnish electrical energy equal to 5000 horse-power, so that when the work that is now under way is completed 50,000 horse-power can be furnished in the form of electricity. About 35,000 horse-power is now actually delivered to the various industrial enterprises. ”

“ 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. ”

“ But as instantly, when the current is stopped, this soft iron core ceases to be a magnet, and becomes as it was before--an inert and ordinary piece of iron. What has just been described is always, in some form, one of the indispensable parts of the electromagnetic machines used in industrial electricity, and in all of them except the appliances of electric lighting, and even in that case it is indispensable in producing the current which consumes the points of the carbon, or heats the filament to a white glow. The current may traverse the wire for a hundred miles to reach this little coil. ”

“ We have just the same effects in electricity. If we place some substance which is practically a non-conductor, or insulator, such as rubber, around an electric wire, or in the path of an electric current, the electricity, acted upon by the volts of pressure, cannot escape, because the insulation keeps it from doing so, just as the iron of the pipe keeps the [7] water from escaping. Thus, you see, the volt does not itself represent electricity, but only the pressure which forces it through the wire. ”

“ Thus, when the insulation of a submarine cable is tested, the insulation appears to improve as the electrification continues.
Thermal phenomena of a kind at first sight analogous take place in the case of the conduction of heat when the opposite sides of a body are kept at different temperatures. In the case of heat we know that they depend on the heat taken in and given out by the body itself. Hence, in the case of the electrical phenomena, it has been supposed that electricity is absorbed and emitted by the parts of the body. ”

“ It is found that when the electromotive force begins to act, the current, as indicated by the galvanometer, is by no means constant. The first effect is of course a transient current of considerable intensity, the total quantity of electricity being that required to charge the surfaces of the insulator with the superficial distribution of electricity corresponding to the electromotive force. ”

“ So, if we bring the two carbons in an arc-lamp together they really form part of the [72] wire, and do not interrupt the current in its travels, but, if we separate the carbons, we make a gap which the current must jump across if it wants to go on. As the volts, or pressure, is so great, the current must jump, and this against the resistance or opposition in an arc-lamp is that which gives the current so much work to do. ”