In the earliest the conductor was represented by long metal wires, supported by silk or other insulating material, and left to pick up the air's potential.
Thomson (Lord Kelvin) at a meeting of the Philosophical Society of Glasgow in 1854, because its greater flexibility renders it less likely to damage the insulating envelope during the manipulation of the cable.
17 and a thickness of insulating material which formerly would have been considered quite insufficient is now very generally adopted with complete success.
At an intermediate O _ _ O or wayside station W, a a B = a `_ " switch " S, consisting of three blocks of brass fixed to an insulating © © © base, is sometimes used FIG.
4), in an early form, consisted of a cell of insulating material having at its bottom a flat-headed platinum screw G; on the top of G was a layer of carbon powder C, on the top of that a platinum disk D, and above that again, forming the cover of the cell, a disk of ivory B, held in position by a ring E.
This was constructed of a shallow box placed in a vertical position, with metallic front and back and insulating sides.
The microphonic portion of the transmitter is contained in a thin cylindrical box or case of brass A, the inner curved surface of which is covered with an insulating layer of paper.
Ebonite takes a fine polish, and is valuable to the electrician on account of its insulating properties, and to the chemist and photographer because vessels made of it are unaffected by most chemical reagents.
For various purposes a manufactured material known as "micanite" or "micanite cloth" is much used; this consists of small sheets of mica cemented with shellac or other insulating cement on cloth or paper.
In conjunction with Josiah Latimer Clark, with whom he entered into partnership in 1861, he invented improved methods of insulating submarine cables, and a paper on electrical standards read by them before the British Association in the same year led to the establishment of the British Association committee on that subject, whose work formed the foundations of the system still in use.
Cavendish proved it by enclosing a metal sphere in two hemispheres of thin metal held on insulating supports.
In another form, a revolving contact is used driven by an electric motor, which consists of an insulating disk having on its surface slips of metal and three wire brushes a, b, c (see fig.
Nansen perfected the instrument, adapting it not only for enclosing a portion of water at any desired depth, but by a series of concentric divisions insulating in the central compartment water at the temperature it had at the moment of collection.
For the purpose of measuring resistances up to a few thousand ohms, the most convenient appliance is a Wheatstone's Bridge (q.v), but when the resistance of the conductor to be measured is several hundred thousand ohms, or if it is the resistance of a so-called insulator, such as the insulating covering of the copper wires employed for distributing electric current in houses and buildings for electric lighting, then the ohmmeter is more convenient.
1, where W represents a portion of the wiring of the building and I a portion of the insulating materials surrounding it.
To prevent leakage over the surface of the insulating covering of the wire which projects above the surface of the water, it is necessary to employ a " guard wire P, which consists of a piece of fine copper wire, twisted round the extremity of the insulated wire and connected to the battery.
On the 6th of May he makes further experiments, and concludes: "Hence I see no reason to expect that any kind of structure or tension can be rendered evident, either in decomposing or non-decomposing bodies, in insulating or conducting states."
It was also necessary to give the fine charcoal a thin coating of calcium oxide by soaking it in lime-water, for the temperature was so high that unless it was thus protected it was gradually converted into graphite, losing its insulating power and diffusing the current through the lining and walls of the furnace.
3), each two inches in diameter and separately supported on insulating arms in the same plane, so that a third revolving plate B may pass very near them without touching.
The axis N 0 passes through the brass piece M, which stands on an insulating pillar of glass, and supports the plates A and C. At one extremity of this axis is the ball D, and the other is connected with a rod of glass, N P, upon which is fixed the handle L, and also the piece G H, which is separately insulated.
4), consisted of two curved metal plates between which revolved a pair of balls carried on an insulating stem.
Tudsbury that if an influence machine is enclosed in a metallic chamber containing compressed air, or better, carbon dioxide, the insulating properties of compressed gases enable a greatly improved effect to be obtained owing to the diminution of the leakage across the plates and from the supports.
The acid process goes on much faster, because in it the heat insulating layer of slag is much thinner.
The ebullition from the formation of carbonic oxide puffs up the resultant phosphoric slag enough to make most of it run out of the furnace, thus both removing the phosphorus permanently from danger of being later deoxidized and returned to the steel, and partly freeing the bath of metal from the heat-insulating blanket of slag.
The plates are placed in a vessel full of insulating oil which prevents the glow or brush discharge taking place over their edges.
For the purpose of a standard condenser a number of concentric metal tubes may be arranged on an insulating stand, alternate tubes being connected together.
On insulating the lower plate and raising the upper plate by the glass handle, the capacity of the condenser formed by the plates is vastly decreased, but since the charge on the lower plate including the gold leaves attached to it remains the same, as the capacity of the system is reduced the potential is raised and therefore the gold leaves diverge widely.
In examining the dissipation which takes place along imperfectly insulating substances, he found that a thread of gum-lac was the most perfect of all insulators; that it insulated ten times as well as a dry silk thread; and that a silk thread covered with fine sealing-wax insulated as powerfully as gum-lac when it had four times its length.
Volta then proved that all metals could be arranged in an electromotive 1 Modern researches have shown that the loss of charge is in fact dependent upon the ionization of the air, and that, provided the atmospheric moisture is prevented from condensing on the insulating supports, water vapour in the air does not per se bestow on it conductance for electricity.
In 1876, Paul Jablochkov (1847-1894), a Russian officer, passing through Paris, invented his famous electric candle, consisting of two rods of carbon placed side by side and separated from one another by an insulating material.
In the form of standard coil recommended by the Berlin Reichsanstalt the coil is immersed in an insulating oil which is kept stirred by means of a small electric motor during the time of making the measurement.