Electrical wire

“ 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 has already been explained that wires offer resistance to an electrical current, and that some of the energy is lost in passing through a wire because of this resistance. Small wires possess more resistance than large ones, and if small wires are to be used, in order to save on the cost of the transmission line, the loss of energy will be greater, necessitating some method of partially reducing or overcoming this fault. ”

“ It is very easy to detect the electric lines which radiate from every part of such a wire when a spark jumps between the terminals S of the coil. All that is necessary to do is to pass the wire through a sensitive film and to develop the film. The accompanying photograph (Fig. 3) was taken at the top of such a wire, by means of a very powerful apparatus at my command. When the photograph is examined with a microscope the arborescent electric lines radiating from the wire, like the rays of light Fig. 2a represents a more complete electrical arrangement of the receiver circuit. ”

“ If the needle can be soldered to a metal stand, or the cork covered with tinfoil, the wire is not needed. On rubbing the paper and placing it on the tray, the electricity passes up the wire into the needle, thence into the wire cross, and escapes by the bent portions of the wires, each of which should be filed to a point. In escaping it electrifies the surrounding air, and this, according to the law that “like electricities repel each other,” has a reacting force on the wire arms. Accordingly the windmill begins to turn, and may attain a tolerable rate of speed if the tray is strongly charged. ”

“ The energy of the currents and the quality of the wire also affect the speed. Until lately it was supposed that the wire acts only as a conductor of electricity, and that a long wire must produce a weaker effect than a short one, on account of the consequent attenuation of the electrical influence; but it is now known that, the cable being a reservoir as well as a conductor, its electrical supply is increased in proportion to its length. ”

“ No. 24 wire is a good size to use; it can be cotton-covered or, preferably, silk-covered, as in the latter case the insulation is better. Begin by making a hole near the roller in the circle of cardboard that is next to the end where the hole for the screw has been made. Pass about three inches of wire through the hole and then wind it evenly on over the tracing paper from end to end and back again. You ought to have five or six layers of it; an ounce, or an ounce and a half, of wire will probably be enough. When it is all on, make another hole in the disc and pass out the wire. ”

“ The wire may be wound on by hand, but a winder (App. 93) will do much better and quicker work.
APPARATUS 84.
113. Horseshoe Electro-Magnet. Fig. 58. Bend soft iron wires, and make a bundle of them. If you wish to wind the wire around spools, the bundle cannot be very large. It will be found best to make the bundle about 3⁄8 in. in diameter, and not to use the spools. Strong paper should be wrapped once or twice around the legs of the horseshoe, and the insulated wire, say 4 layers, can then be wound directly upon this. ”

“ The annunciator has a bell to call attention. A cable of six wires enters this annunciator (Fig. 36) . One wire goes direct to the bell and the other five reach the bell through the separate coils of the electro-magnets which control the drops. But how are [70] electrical connections made between a moving elevator car and the push buttons on various floors? The diagram in Fig. 37 shows this in elevation. B represents a battery of several dry cells located in the basement. One wire from it runs direct to the push buttons 1, 2, 3, 4, 5, located upon the five floors of the house. ”

“ These wires are connected with the brushes of a commutator, K, on the engine-shaft, which commutator is in electrical connection with the poles of a battery, dynamo-electric machine, or other source of electricity. Instead of two wires to produce a spark, a single wire may be arranged to become incandescent at the proper time for ignition. ”

“ It is well to have 1⁄2 lb. of No. 24 or 25 for electro-magnets, current-detectors, etc., etc. 1⁄2 lb. of No. 30 will not be too much, if you make induction coils. If you handle your wire carefully, single cotton-covered will do. Double cotton-covered is better than single, but it costs more. Be careful not to injure the covering. (See below for splicing wire.) Look out for broken wire.
288. Splicing Wire. Fig. 125. Do not simply touch [Pg 140] two wires together and imagine that you have a good connection; a mere twist is not sufficient. ”

“ Just here we may refer to the fact—for it is a fact—that the electrical energy transmitted over a line, which may be many miles in length, really does not travel by the wire connecting the two points. It travels in the ether surrounding the wire. The wire itself is, in fact, the guiding core of the disturbances in the ether which proceed outward in all directions to unlimited distances. The guiding core or conducting wire is needed to focalize or direct the delivery of the energy. ”

“ Ans. It is not adapted to outside work.
Safe Carrying Capacity of Wire.—All wires will heat when a current of electricity passes through them. The greater the current or the smaller the wire, the greater will be the heating effect. Large wires are heated comparatively more than small wires because the latter have a relatively greater radiating surface.
Fig. 815.—Pothead wires. The standard wire for pothead work is either No. 19, 20 or 22 B. & S. gauge, either single conductor or twisted pair, insulated to a diameter of 3/32 inch over rubber, without any outer braid or protection. ”

“ It is evident that if a wire from one pole of [Pg 76] a battery be connected with the binding-post, it will also be electrically connected with the tin strip and nails. By touching the wire from the other battery-pole to the tin or to any nail, the circuit will be closed. If this last-mentioned wire be drawn along entirely above the tin, so that its end can bump along from one nail to another, you can see that the current will be closed every time a nail is touched, and be opened every time it jumps through the air. ”

“ A piece of copper wire is pierced through the center of a sheet of cardboard, and carried vertically for two or three feet then bent around to the terminals of a battery or other source of current. If iron filings be sprinkled over the card while the current is passing, they will arrange themselves in circles around the wire, thus indicating the form of the magnetic field surrounding the conductor. Compass needles may also be used to show the direction of the lines of force at any point. ”

“ Fig. 175. The Leyden jar and brass wire discharger.
Thirty-sixth Experiment.
The jar is silently discharged if the balls are removed from the discharger and points used instead; so, also, the whole of the electricity produced by an electrical machine in full action may be readily drawn off by a pointed conductor, such as a needle, placed at the end of a brass wire. Electricity passes much more rapidly through points than rounded surfaces, hence the reason why all parts of electrical apparatus are free from sharp points and rough asperities. ”

“ It sometimes happens that after using power from the local electric illuminating company for some time, conditions arise which make it expedient for the owners to install a private electric plant. If a straight three wire system had been originally installed, the mains and the feeders when used on a two wire system would not be heavy enough by 25 per cent., as the neutral wire of a straight three wire system is the same in size as one of the two outer wires, and theoretically carries one-half the current or less. ”

“ To avoid as much as possible cutting uselessly, let every binding screw be examined and tightened up, and every length of wire, which it is possible to get at, be tested for continuity before any "slashing" at the wires, or furious onslaughts on the indicator be consummated.
In conclusion, I beg to record my thanks for the very generous assistance which I have received in the compilation of the foregoing pages from the electrical firms of Messrs. Blakey Emmot, Binswanger, Gent, Judson, Jensen, and Thorpe. ”

“ The wires should be attached with tie wires having an insulation equal to that of the conductor which it secures to the knob. The use of split knobs does away with the necessity of using tie wires. The conductors must be at least 5 inches apart and it is better to support them on separate beams when possible. Each wire must be encased in a piece of flexible tube at all switches, outlets, etc., and this piece of tubing should be sufficiently long to extend from the last insulator and project at least one inch beyond the outlet. ”

“ Binding-Post. Fig. 28. Two copper or tin strips fastened at one end by a screw, the upper strip being bent a little at one end, make a connector that is useful for some purposes, where you want to make and break the connection frequently. The bare end of the wire which belongs to the apparatus is fastened under the screw-head. The outside wire, or wires, to be connected are pushed between the strips of metal. Another way is to fasten the outside wire to a strip of metal about 1⁄2 in. ”

“ Hold the bundle of wires in a vise, and file the ends smooth, before winding on the wire. Paraffine should be used to hold the turns of insulated wire together.
APPARATUS 83.
112. Electro-Magnet. Fig. 57. An electro-magnet with a removable core may be made by winding the wire [Pg 53] on a spool. The core is made, as in App. 82, of soft iron wires, bound together with stout thread. A bolt may be used instead of the wire, but the wire loses its magnetism much quicker than a soft steel bolt would. ”

“ The quantity of electricity transmitted is therefore less, and the comparative intensity of it is greater.
Another difficulty attending the use of insulated wires buried in the ground arises from a very peculiar condition of electrical conduction, that could scarcely165 have been anticipated. The wire, coated with gutta percha, and surrounded externally with water or with moist earth, becomes an elongated Leyden jar; the gutta percha representing the glass, the wire the inside coating, and the water the conducting surface outside. ”

“ Q shows a stout wire or strip of 2 or 3 thicknesses of tin. Suppose we have an apparatus, as, for example, an electric bell, which we want to have ring when someone at a distance desires to call us. If we use a telephone or telegraph instrument we shall want to cut the bell out of the circuit as soon as we hear the call and are ready to talk. Suppose the current comes to us through the wire, A, Fig. ”

“ So long as the two plates of metal are not otherwise connected there is no electricity in evidence, but when the two are joined by any metal conductor, as, for example, a piece of wire—thus, in common parlance, "completing the circuit"—a current of electricity flows about this circuit, passing from the first metal plate to the second, through the liquid and back from the second plate to the first through the piece of wire. ”

“ The insulated wires being drawn into them, any short circuit or heating of the wire cannot give rise to a fire, as it can only take place in the interior of a non-inflammable tube. A third system of electric light wiring is the safety concentric system, in which concentric conductors are used. The inner one, which is well insulated, consists of a copper-stranded cable. The outer may be a galvanized iron strand, a copper tape or braid, or a brass tube, and is therefore necessarily connected with the earth. ”

“ 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. ”

“ Whenever possible, the wiring of a house, etc., for bell work, should be done as soon as the walls are up and the roof is on. The shortest and straightest convenient route from bell to battery, etc., should always be chosen where practicable to facilitate drawing the wire through and to avoid the loss of current which the resistance of long lengths of wire inevitably entails. The wires should be run in light zinc tubes nailed to the wall. ”

“ Iron which is brought near a spiral of copper wire, traversed by an electrical current, becomes magnetic, and then attracts other pieces of iron, or a suitably placed steel magnet. ”

“ On most, if not all, transmission lines the guard wire or wires, if used at all, are placed either above or on a level with the highest power conductors. With one conductor of a three-phase circuit mounted on a pin set in the top of a pole, and the two remaining conductors on a two-pin cross-arm beneath, in the method most frequently adopted for transmission lines of very high voltage, it is obviously impracticable to put guard wires either above or on a level with the power circuits. ”