Electrical conductor

“ It has been fully demonstrated by experiment, that no substance which is a conductor can be excited so as to exhibit electrical phenomena: and in the same manner it has been found, that no substance which can be excited, is a conductor. But as we have already hinted, there is, strictly speaking, no substance which is a perfect conductor or non-conductor; because, on the one hand, the electric fluid meets with some resistance in its passage through the best conductors ”

“ In many electrical instruments a wire grating is used to prevent certain parts of the apparatus from being electrified by induction. We know that if a conductor be entirely surrounded by a metallic vessel at the same potential with itself, no electricity can be induced on the surface of the conductor by any electrified body outside the vessel. ”

“ 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. ”

“ In the first place, in moving a current of electricity to and from a coil of wire, or any other conductor, or (which is the same thing, since action and reaction are equal and opposite) in moving a coil of wire or any other conductor to and from a current of electricity, a sense of resistance will be experienced, and energy will have to be spent upon the process; in the second place, an electrical current will be generated in the conductor, and the conductor will be heated in consequence. ”

“ Bodies in which the electric current moves freely are called conductors, and those in which it does not move freely are called insulators. There is, however, no substance so good a conductor as to be devoid of resistance, and no substance of such high resistance as to be a non-conductor. ”

“ In use either the prime conductor or cushions are connected by a chain
or otherwise with the earth. Assume it to be the cushions. As the
machine is worked by turning the plate, the glass and cushion being in
contact develop opposite electricities. The glass is charged with
positive electricity, and as it turns carries it off and as it reaches
the prime conductor by induction and conduction robs it of its negative
electricity. Meanwhile the cushions negatively excited deliver their
charge to the earth. The action thus goes on, the prime conductor being
charged with positive electricity. ”

“ Form a communication by a chain from the coating to the cushion, and the phial will charge.
For the globe then draws the electrical fire out of the outside surface of the phial, and forces it, through the prime conductor and wire of the phial, into the inside surface. ”

“ Fig. 24.—Lines of force of a charged sphere and a conductor under induction. The negative electrification on the end a of the cylinder indicates that a certain number of lines end there, while the positive electrification on the end b similarly indicates that an equal number of lines set out from that end. It is one of the fundamental properties of a conductor that it yields instantly to the smallest electric force, and that no electric force can be permanently maintained within the substance of a conductor in which no current is passing. ”

“ It is a very good conductor of electricity and, (2d.) It will undergo little or no change of property by lying ever so long in the earth. Thus might the surface of that part of the conductor, in contact with the earth, be increased, with little trouble or expense to any extent at pleasure; a circumstance which every one acquainted with electrical experiments, must acknowledge to be of great importance to the end here proposed.”
The following experiments with a thunder-house, shew the utility of lightning rods, and ascertain what termination of the rod best answers the end proposed. ”

“ Thus, if we take an insulated metallic conductor in the uncharged state, and bring it near an electrified body, we shall find that the conductor, while still at a considerable distance, will give signs of an electrical charge. Suppose we have a cylindrical conductor, and that we present one end of it to the electrified body, but at such a distance that no spark shall pass, we shall find, if the charge on the electrified body be strong and the conductor be brought sufficiently near, that on bringing the finger near the insulated cylinder, a spark passes. ”

“ From these experiments, the conclusion is that when a conductor is brought near a charged body, the end away from the inducing charge is electrified with the same kind of electricity as that on the inducing body, while the end toward the inducing body receives electricity of opposite sign. ”

“ The resistance thus interposed between the ground and the conductor is such that any voltage very much in excess of the maximum normal will cause a discharge to ground, whereas at other times the conductor is ungrounded because of the air gap. ”

“ In the case, therefore, of the electrical machine, it appears that the accumulation of electricity in an insulated conductor is always accompanied by the excitement of the contrary electricity in the surrounding atmosphere, and in every conductor placed near the former conductor. It does not seem possible, in this case, to produce one electricity by itself. ”

“ Around the prime conductors of an electrical machine the atmosphere to some distance, or any conducting surface suspended in that atmosphere, is found to be in an electric condition opposite to that of the prime conductor itself. Near and around the positive prime conductor there is negative electricity, and near and around the negative prime conductor there is positive electricity. When pith balls are brought near to either of the conductors, they become electrified with the opposite electricity to it ”

“ In the ordinary construction of transmission lines on land the tensile strength of wire is secondary in importance to its electrical conductivity, because supports can be spaced according to the strength of the conductor used. ”

“ If an insulated conductor, connected with the positive conductor of an electrical machine, have a metal rod 0.3 of an inch in diameter projecting from it outwards from the machine, and terminating by a rounded end or a small ball, it will generally give good brushes; or, if the machine be not in good action, then many ways of assisting the formation of the brush can be resorted to ”

“ 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 {78}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. ”

“ After demonstrating the practicability of this method of transmission, the thought naturally occurred to me to use the earth as a conductor, thus dispensing with all wires. Whatever electricity may be, it is a fact that it behaves like an incompressible fluid, and the earth may be looked upon as an immense reservoir of electricity, which, I thought, could be disturbed effectively by a properly designed electrical machine. Accordingly, my next efforts were directed toward perfecting a special apparatus which would be highly effective in creating a disturbance of electricity in the earth. ”

“ A disused and abandoned electric conductor, such as a telegraph
wire.
(c) A wire in use, but through which, at the time of speaking, no
current is passing.
Death, Electrical.
Death resulting from electricity discharged through the animal system.
The exact conditions requisite for fatal results have not been
determined. High electro-motive force is absolutely essential; a
changing current, pulsatory or alternating, is most fatal, possibly
because of the high electro-motive force of a portion of each period. ”

“ A stout wire will transfer a bigger quantity in unit time than a thin wire, or, as we may also say, it is able to carry a bigger current. When it is a question of electricity in motion the conductor must have body, whilst as we have seen, with electricity at rest only the surface counts, or, to speak more correctly, only the capacity counts. ”

“ If the electrified tray is touched with the sealing-wax or ebonite rod, it will not be discharged, but if touched with a metal wire, the hand, or a damp thread, it is discharged at once. This shows that some bodies are conductors and others non-conductors or insulators of electricity, and that bodies can be electrified by friction and impart their electric charge to other bodies. A charged conductor supported on a non-conductor retains its charge. ”

“ The greater diameter of aluminum over equivalent copper conductors has advantages in transmission with alternating current at very high voltages. At high voltages, say of 40,000 or more, the constant silent loss of energy from one conductor to another of the same circuit through the air tends to become large and even prohibitive in amount. ”

“ But if we connect these wires to the coils of the induction apparatus and then take hold of the two ends of the secondary coil and break and close the primary circuit we should feel a painful shock at each break and close, although the actual amount of current flowing through the secondary wire is not as great as that which flows through the primary; but the voltage (or electromotive force) is higher, and thus is able to drive what current there is through a conductor of higher resistance, such as the human body. ”

“ All wires have a certain resistance per foot, according to the nature of the metal used and the size of the wire—that is to say, the finer the wire the greater number of ohms resistance it has to the foot.
Water and electricity flow under very similar conditions—that is to say, each of them must have a channel, or conductor, and each of them requires pressure to force it onward. Water, however, being a tangible substance, requires a hollow conductor; while electricity, being intangible, will flow through a solid conductor. ”

“ If single-phase or two-phase current is transmitted, each cable should contain the two conductors that go to make up a circuit. In work with alternating currents the use of only one conductor per cable should be avoided because of the loss of energy that results from the currents induced in the metallic sheath of such a cable. ”

“ The best conductors offer some resistance to the passage of the current and the best insulators conduct to some extent. If we make a comparison of electric conductors we find that the metals that conduct heat best also conduct electricity best. This, it seems to me, is a confirmation of the atomic theory of electricity so far as it means anything. If a good conductor, as silver, is subjected to intense cold by putting it into liquid air, its conductivity is greatly increased. It is well known that [Pg 48] heating a conductor ordinarily diminishes its power to conduct electricity. ”

“ In the case of the conducting wire we have the same transfer of electricity from a place of high to a place of low potential without any external work being done. The principle of the Conservation of Energy therefore leads us to look for internal work in the conductor. In an electrolyte this internal work consists partly of the separation of its components. In other conductors it is entirely converted into heat. ”

“ To charge the jar the outside tinfoil is connected with the ground, and the inside is excited by means of the knob from the prime conductor of the machine. The electricity is, as the phrase goes, ‘bottled off,’ though ‘the fluid’ is no fluid, and is not ‘poured’ at all. Two conductors of large surface are separated by a rigid insulator, and hence the conditions are favourable for powerful attraction. ”

“ On the top of a finely-pointed wire, rising perpendicularly from the conductor, let another wire, sharpened at each end, be made to move freely, as on a centre. If it be well balanced, and the points bent horizontally, in opposite directions, it will, when electrified, turn very swiftly round, by the re-action of the air against the current which flows from off the points. ”

“ We find that electromotive force acts differently on various substances when they are subjected to its operation. In some substances electromotive force produces a continuous electric current, and in these cases the material is called a conductor. In other cases electromotive force creates what is called electric strain, or electric displacement, and these substances are generally called non-conductors. ”

“ If you were to use a piece of string instead of a copper wire to go from one pole of a battery to another or to spin between the poles of the magnet of the dynamo, you could get no flow of electricity to speak of. Electrons do not flow through string easily, but they flow through a copper wire very easily. Anything that carries, or conducts, electricity well is called a good conductor. Anything that carries it poorly is called a poor conductor. Anything that allows practically no electricity to pass through it is called an insulator. ”

“ By this we mean that to get the current through the wire the force which is pushing the electricity from one end to the other is much smaller with silver than with lead; silver offers less "resistance" to the flow of electricity than lead. Thus each conductor has a certain physical property called its electric resistance, and this depends on the length and section of the conductor, on its temperature and on its material. In order to compare different materials as regards resistance, we must eliminate those elements which may vary from case to case and reduce all to the same standard. ”