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BATTERY (Fr. batterie, from battles, ...
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See also:BATTERY (Fr. batterie, from battles, to See also:beat) , the See also:action of beating, especially in See also:law the unlawful wounding of another (see See also:ASSAULT). The See also:term is applied to the apparatus used in battering, hence its use in military organization for the unit of See also:mobile See also:artillery of all kinds. This consists of from four to eight guns with their personnel, wagons and See also:train. In the See also:British service the term is applied to See also: In one See also:form, the "voltaic See also:pile," he placed a See also:series of pairs of copper and See also:zinc disks one above the other, separating each pair from the one above it by a piece of See also:cloth moistened with a See also:solution of See also:common See also:salt. In another form, the " couronne de tasses," he took a number of vessels or cells containing brine or dilute See also:acid, and placed in each a zinc See also:plate and a copper plate; these plates were not allowed to See also:touch each other within the vessels, but each zinc plate was connected to the copper plate of the adjoining See also:vessel. In both these arrangements an electric current passes through a See also:wire which is connected to the terminal plates at the two ends of the series. The direction of this current is from copper to zinc; within each See also:cell itself it is from zinc to copper. The plate to which the current flows within the cell is the negative plate, and that from which it flows the See also:positive plate; but the point on the negative plate at which the current enters the See also:external wire is the positive See also:pole, and the point on the positive plate at which it leaves the external See also:circuit the negative pole. During the See also:time that the external connexion is maintained between the two poles and the current passes in the wire, the zinc or positive plates are gradually dissolved, and See also:hydrogen See also:gas is liberated at the See also:surface of the copper or negative plates; but when the external connexion is broken this action ceases. If the materials used in the cells were perfectly pure, probably the cessation would be See also:complete. In practice, however, only impure commercial zinc is available, and with this corrosion continues to some extent, even though the external circuit is not closed, thus entailing See also:waste of material. This " See also:local action" is explained as due to the fact that the impurities in the zinc plate form See also:miniature voltaic couples with the zinc itself, thus causing its corrosion by voltaic action; and an early improvement in the voltaic cell was the See also:discovery, applied by W. See also:Sturgeon in 183o, that the evil was greatly reduced if the surface of the zinc plates was amalgamated, by being rubbed with See also:mercury under dilute sulphuric acid. Another disadvantage of the See also:simple cell composed of copper and zinc in dilute acid is that the current it yields rapidly falls off. The hydrogen formed by the operation of the cell does not all See also:escape, but some adheres as a See also:firm to the negative plate, and the result is the See also:establishment of a See also:counter or reverse electromotive force which opposes the main current flowing from the zinc plate and diminishes its force. This phenomenon is known as "polarization," and various remedies have been tried for the evils it introduces in the See also:practical use of primary batteries. See also:Alfred Smee in 1839 modified the simple copper-zinc couple excited by dilute sulphuric acid by substituting for the copper thin leaves of See also:platinum or platinized See also:silver, whereby the elimination of the hydrogen is facilitated; and attempts have also been made to keep the plates See also:free from the gas by See also:mechanical agitation. The See also:plan usually adopted, however, is either to prevent the formation of the film, or to introduce into the cell some " depolarizer " which will destroy it as it is formed by oxidizing the hydrogen to See also:water (see also See also:ELECTROLYSIS). The former method is exemplified in the cell invented by J. F. See also:Daniell in 1836. Here the zinc stands in dilute sulphuric acid (or in a solution of zinc sulphate), and the copper in a saturated solution of copper sulphate, the two liquids being separated by a porous See also:partition. The hydrogen formed by the action of the cell replaces copper in the copper sulphate, and the displaced copper, instead of the hydrogen, being deposited on the copper plate polarization is avoided. The electromotive force is about one volt. This cell has been constructed in a variety of forms to suit different purposes.- In a portable form, designed by See also:Lord See also:Kelvin in 1858, the copper plate, soldered to a See also:gutta-percha covered wire, is placed at the bottom of a See also:glass vessel and covered with crystals of copper sulphate; over these wet sawdust is sprinkled, and then See also:mere sawdust, moistened withsolution of zinc sulphate, upon which is plated the zinc plate. The Minotto cell is similar, except that See also:sand is substituted for sawdust. In these batteries the sawdust or sand takes the See also:place of the porous See also:diaphragm. 
In another class of batteries the diaphragm is dispensed with altogether, and the action of gravity alone is relied upon to retard the interdiffusion of the liquids. The cell of J. H. Meidinger, invented in 1859, may be taken as a type of this class. The zinc is formed into a See also:ring which fits the upper See also:part of a glass See also:beaker filled with zinc sulphate solution. At the bottom of the beaker is placed a smaller beaker, in which stands a ring of copper with an insulated connecting wire. The mouth of the beaker is closed by a lid with a hole in the centre, through which passes the See also:long tapering See also:neck of a glass See also:balloon filled with crystals of copper sulphate; the narrow end of this neck dips into the smaller beaker, the copper sulphate slowly runs out, and being specifically heavier than the zinc sulphate it collects at the bottom about the copper ring. In Lord Kelvin's See also:tray-cell a large wooden tray is lined with See also:lead, and is covered at the bottom with copper by See also:electrotyping. The zinc plate is enveloped in a piece of See also:parchment See also:paper See also:bent into a tray shape, the whole resting on little pieces of See also:wood placed on the bottom of the leaden tray. Copper sulphate is fed in at the edge of the tray and zinc sulphate is poured upon the parchment. A battery is formed by arranging the trays in a stack one above the other. Various combinations have been devised in which the hydrogen is got rid of more or less completely by oxidation. See also:Sir W. R. See also: A zinc See also:rod constitutes the positive plate, and the exciting fluid is a solution of sal-ammoniac. Sometimes no porous pot is employed, and the manganese dioxide and granulated carbon are agglomerated into a solid See also:block round the carbon plate. The electromotive force is about one and a See also:half volt. The cell is widely used for such purposes as ringing electric bells, where current is required intermittently, and for such service it will remain effective for months or years, only needing water to be added to the See also:outer See also:jar occasionally to replace loss by evaporation. On a closed circuit the current rapidly falls off, because the manganese dioxide is unable to oxidize all the hydrogen formed, but the cell quickly recovers after polarization. The so-called " dry cells," which came into considerable use towards the end of the 14th See also:century, are essentially Leclanche cells in which the solution is See also:present, not as a liquid, but as a See also:paste formed with some absorbent material or gelatinized. See also:Black See also:oxide of copper is another solid depolarizer, employed in the See also:Lalande cell. In the See also:Edison-Lalande form the copper oxide is suspended in a See also:light copper See also:frame. The exciting solution consists of one part of See also:caustic soda dissolved in three parts by See also:weight of water, and to prevent it from being acted on by the carbonic acid of the See also:air it is covered with a layer of See also:petroleum oil. Sodium zincate, which is soluble, is formed by the action of the cell, and the hydrogen produced is oxidized by See also:oxygen from the copper oxide. The electromotive force may be about one volt initially, but in practice only about three-quarters of a volt can be relied on. Primary cells form a convenient means of obtaining electricity for laboratory experiments, and for such light services as working telegraphs, bells, &c.; but as a source of the heavy currents required for electric See also:lighting and See also:traction they are far too expensive in operation, apart from other considerations, to compete with dynamoelectric machinery driven by See also:steam or water See also:power. Certain forms, known as " See also:standard cells," are also used in See also:electrical measurements as See also:standards of electromotive force (see See also:POTENTIOMETER).
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