Fig. 111. SWINBURNE'S HEDGEHOG TRANSFORMER.

150 STANDARD ELECTRICAL DICTIONARY.

Co-ordinates, System of.

A system for indicating the position of points in s.p.a.ce by reference to fixed lines, intersecting at a determined and arbitrary point 0, termed the origin of co-ordinates. In plane rectangular co-ordinates two lines are drawn through the origin, one horizontal, termed the axis of abscissas, or axis of X. All distances measured parallel to it, if unknown, are indicated by x, and are termed abscissas. The other axis is vertical, and is termed the axis of ordinates, or axis of Y. All distances measured parallel to it, if unknown, are indicated by y and are termed ordinates. Thus by naming its abscissa and ordinate a point has its position with reference to the axes determined, and by indicating the relation between a point, line or curve, and a system of abscissas and ordinates, the properties of a line or curve can be expressed algebraically. Co-ordinates may also be inclined to each other at any other angles, forming oblique co-ordinates; relations may be expressed partly in angles referred to the origin as a centre, giving polar co-ordinates. For solid geometry or calculations in three dimensions, a third axis, or axis of Z, is used, distances parallel to which if unknown are indicated by z.

Fig. 112. AXES OF CO-ORDINATES.

151 STANDARD ELECTRICAL DICTIONARY.

Cooling Box.

In a hydroelectric machine, q. v., a conduit or chest through which the steam pa.s.ses on its way to the nozzles. Its object is to partially condense the steam so as to charge it with water vesicles whose friction against the sides of the nozzles produces the electrification .

152 STANDARD ELECTRICAL DICTIONARY.

Copper.

A metal; one of the elements. Symbol, Cu; atomic weight, 63.5; equivalent, 63.5 and 31.75; valency, 1 and 2; specific gravity, 8.96.

It is a conductor of electricity, whose conductivity is liable to vary greatly on account of impurities.

Annealed. Hard drawn.

Relative resistance (Silver = 1), 1.063 1.086 Specific resistance, 1.598 1.634 microhms.

Resistance of a wire at 0? C. (32? F.), Annealed. Hard Drawn.

(a) 1 foot long, weighing 1 grain, .2041 ohms .2083 ohms.

(b) 1 foot long, 1/1000 inch thick, 9.612 " 9.831 "

(c) 1 meter long, weighing 1 gram, .1424 " .1453 "

(d) 1 meter long, 1 millimeter thick, .02034 " .02081 "

microhm. microhm.

Resistance of 1 inch cube at 0?C. (32? F.) .6292 .6433

Percentage of resistance change, per 1? C. (1.8? F.) at about 20? C. (68? F.) = 0.388 per cent.

Electro-chemical Equivalent (Hydrogen = .0105) Cuprous .6667 Cupric .3334

In electricity it has been very extensively used as the negative plate of voltaic batteries. It has its most extensive application as conductors for all cla.s.ses of electrical leads.

Copper Bath.

A solution of copper used for depositing the metal in the electroplating process. For some metals, such as zinc or iron, which decompose copper sulphate solution, special baths have to be used.

The regular bath for copper plating is the following:

To water acidulated with 8 to 10 percent. of sulphuric acid as much copper sulphate is added as it will take up at the ordinary temperature.

The saturated bath should have a density of 1.21. It is used cold and is kept in condition by the use of copper anodes, or fresh crystals may be added from time to time.

For deposition on zinc, iron, tin and other metals more electropositive than copper, the following baths may be used, expressed in parts by weight:

Tin Iron and Steel. Cast Iron Cold Hot. and Zinc. Zinc.

Sodium Bisulphate, 500 200 300 100 Pota.s.sium Cyanide, 500 700 500 700 Sodium Carbonate, 1000 500 --- --- Copper Acetate, 475 500 350 450 Aqua Ammoniae, 350 300 200 150 Water, 2500 2500 2500 2500

These are due to Roseleur.

153 STANDARD ELECTRICAL DICTIONARY.

Copper Stripping Bath.

There is generally no object in stripping copper from objects. It can be done with any of the regular copper baths using the objects to be stripped as anode. The danger of dissolving the base itself and thereby injuring the article and spoiling the bath is obvious.

Cord Adjuster.

A device for shortening or lengthening the flexible cord, or flexible wire supplying the current, and by which an incandescent lamp is suspended. It often is merely a little block of wood perforated with two holes through which the wires pa.s.s, and in which they are retained in any desired position by friction and their own stiffness.

Fig. 113. FLEXIBLE CORD ADJUSTER.

Cord, Flexible.

A pair of flexible wire conductors, insulated lightly, twisted together and forming apparently a cord. They are used for minor services, such as single lamps and the like, and are designated according to the service they perform, such as battery cords, dental cords (for supplying dental apparatus) and other t.i.tles.

Core.

(a) The conductor or conductors of an electric cable. (See Cable Core.)

(b) The iron ma.s.s, generally central in an electro-magnet or armature, around which the wire is coiled. It acts by its high permeance to concentrate or multiply the lines of force, thus maintaining a more intense field. (See Armature--Magnet, Electro--Magnet, Field--Core, Laminated). In converters or transformers (See Converter) it often surrounds the wire coils.

Core-discs.

Discs of thin wire, for building up armature cores. (See Laminated Core.) The usual form of core is a cylinder. A number of thin discs of iron are strung upon the central shaft and pressed firmly together by end nuts or keys. This arrangement, it will be seen, gives a cylinder as basis for winding the wire on.

Core-discs, Pierced.

Core-discs for an armature of dynamo or motor, which are pierced around the periphery. Tubes of insulating material pa.s.s through the peripheral holes, and through these the conductors or windings are carried. The conductors are thus embedded in a ma.s.s of iron and are protected from eddy currents, and they act to reduce the reluctance of the air gaps.

From a mechanical point of view they are very good. For voltages over 100 they are not advised.

Synonym--Perforated Core-discs.

154 STANDARD ELECTRICAL DICTIONARY.