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but flow always in the same direction it is termed a "pulsating" current. If an electrical charge flowing in one direction is followed by another charge flowing in the opposite direction, an “alternating” current is produced.

Cutout.-An electro-magnetic mechanism that automatically performs the same function of opening a closed circuit that a hand-operated switch does.

Discharge.—The flow of electric current from a battery through a circuit. The opposite of “charge.'

Distilled Water.—The condensed water vapor or steam obtained by cooling vapors given off from boiling water. This will remove the impurities, such as salts, etc. These remain in the still as residue, only chemically pure water being vaporized.

Dynamo.-An electrical machine capable of producing current and distributing this current as desired, providing the current is sufficiently strong to overcome the resistance to its motion of the parts comprising the external circuit.

Electrolyte.—The fluid in a battery cell, consisting of specially pure sulphuric acid diluted with pure water in some cases and an alkaline solution in others.

Element.-One positive group and one negative group with separators, assembled together.

Electric Contact.—The joining of two conductors so a current can pass from one to the other.

Electrode.—The terminal of any open circuit.

Electrolysis.—The separation of a chemical compound into its con. stituents, by the action of an electric current. It cannot take place unless this compound is a conductor of electricity.

Electro-Magnet.—A bar of iron magnetized by passing a current of electricity through a coil of insulated wire wrapped around it. When the current is interrupted the iron bar or core piece ceases to possess magnetic qualities.

Electrical Distribution.—The action of an electrical machine in regulating the distribution of electricity may be considered to be the same as that of a pump which takes water from one tank and supplies it to another at a higher level. If for these reservoirs we consider bodies insulated from each other, we can, with an electrical generator, take electricity from one that has been overcharged and supply it to another which is undercharged.

Electricity.-A force that no one knows the exact nature of. To form some conception of this force, it is well to consider that we are able to place various bodies in different electrical relations. A stick of sealing wax or a hard rubber comb rubbed on a coat sleeve will attract bits of paper, feathers and other light objects. The sealing wax or rubber is said to be charged with electricity which has been produced by friction against the coat sleeve. Electricity may be produced by mechanical, chemical or thermal action.

Electrical Charge.—Any body charged with electricity may be considered one whose surface is supplied with either an overcharge or undercharge of electricity. The overcharged body always tends to discharge to the undercharged body in order to equalize a difference in pressure existing between them.

Filling Plug.—The plug which fits and closes the orifice of the filling tube in the cell cover.

Flushing.—Replacing electrolyte in lead-plate cells with acid instead of distilled water.

Flooding.–Overflowing through the filling tube. With the usual vent this can occur only when a battery is charged with the filling plug out.

Freshening Charge.-A charge given to a battery which has been standing idle, to insure that it is in a fully charged condition.

Forming.—The process of making storage-battery plates from lead sheets by a series of charging and discharging operations.

Fuse Box or Fuse Block.-A non-conducting container for safety fuses, usually of porcelain, slate or marble.

Fuse.—An electrical safety valve to prevent an overload or passage of excessive amounts of current through a circuit. These are made of fusable lead alloy wire, which melts or “blows” if too much current is passed through it, thus breaking the circuit in which it is placed.

Gassing.—The bubbling of the electrolyte caused by the rising of gas set free toward the end of the charge.

Generator System.-An equipment including a generator for automatically recharging the battery, in contradistinction to a straight storage system, where the battery has to be removed to be recharged or coupled to an external current source.

Glass.-A fused mixture of silicate of various oxides, and a very good non-conductor of electricity if dry. Not affected chemically. by most acids or alkali. May be made either opaque or transparent, depending upon coloring matter added. A very common, brittle substance, widely used for storage battery and primary cell jars, insulators and containing vessels for all kinds of liquids.

Gravity.--A contraction of the term “specific gravity," which means the density compared to water as a standard.

Grid.—The metal framework of a plate supporting the active material, and provided with a lug for conducting the current and for attachment to the strap.

Group.-A set of plates, either positive or negative, joined to a strap. Groups do not include separators.

H,0.—Chemical symbol for water.

Hard Rubber.-A rubber compound that has been hardened by heat treatment so it has greater stiffness than rubber in its natural form, and will keep its shape indefinitely after forming. This material is very brittle and not very strong. It is an excellent insulator of electricity, and as it is not affected by sulphuric acid it is widely used for cell jars.

Hold-Down Clips.—Brackets for the attachment of bolts for holding the battery securely in position on the car.

Horse-Power.—The accepted unit of mechanical work. The ability to move 550 pounds one foot in one second or 33,000 pounds one foot in one minute. An electrical horse-power is 746 watts.

H.P.-Abbreviation for horse-power.

Hydrogen.-One of the basic elements existing as a gas under natural conditions. It inay be liquefied by the simultaneous application of great pressure and abstraction of heat. It is the lightest known substance. The chemical symbol is H.

Hydrogen Flame.—A very hot and clean flame of hydrogen gas and compressed air used for making burned connections.

Hydrogen Generator.-An apparatus for generating hydrogen gas for lead-burning

Hydrometer.-An instrument for measuring the specific gravity of the electrolyte.

Hydrometer Syringe.--A glass barrel enclosing an hydrometer and provided with a rubber bulb for drawing up electrolyte.

Induction.—The creation of a current in a conductor not connected to a source of electricity by the juxtaposition of one that is carrying the current.

Induction-Magnetic.—The magnetization of any magnetic substance, such as iron or steel, by placing it in a magnetic field but not in actual contact with the energizing magnet.

Insulating Twpe.-A textile fabric impregnated with insulating compound of an adhesive nature. Used to cover bare spots in insulated wires, re-enforce insulation, and for protecting joints where wires are joined together.

Insulating Varnish.—Shellac or sealing wax dissolved in alcohol, or gum copal dissolved in ether, may be used as a varnish for insulating purposes.

Insulator.—Materials such as wood, glass, rubber, etc., and air, conduct electricity so badly as to be termed insulators. What would normally be an insulator to a current of low potential may be ruptured by a current of higher potential or pressure which can break down the resistance.

Iron Oxide.-Commonly known as “rust." It is packed in steel pockets, which are assembled into negative plates of Edison Storage Battery. Expressed chemically as Feo.

Jar.—The hard rubber container holding the element and electrolyte. KOH.—Chemical symbol for caustic potash or potassium hydrate.

Lead.-An abundant and widely used metal of bluish-white color, and one of the softest and heaviest of metals. It is not acted upon by sulphuric acid unless an electric current is passed through it. It forms the main part of most storage-battery plates, either as a metallic lead or as a lead oxide.

Lead-Burning.-Making a joint by melting together the metal of the parts to be joined.

Lead Oxide.—Material on plates when a cell is discharged according to some theories of storage-battery action. This is expressed chemically as Pbo, differing from peroxide only because there is less oxygen combined with the lead.

Lead Peroxide.—The active material on positive plates of lead bat. teries after charging. Expressed chemically as PbOz.

Lead Sulphate.—Material on sto ge-battery plates when cells are discharged, caused by absorption of sulphate from the electrolyte. Expressed chemically as PbSOz.

Lime, Slaked.—First quicklime is obtained by burning limestone, chalk or marble in kilns and afterward removing its caustic properties by watering it and allowing it to remain in the air for a time. This is used in battery compartments of electric vehicles to neutralize spilled acid, as it is of an alkaline nature.

Litharge.—A yellow or reddish oxide of lead that is partially fused.

Local Action.—Wasteful oxidization of zinc in a primary battery when it is not in use, or abnormal sulphation of storage-battery plates due to impurities in the electrolyte.

Lug.-The extension from the top frame of each plate, connecting the plate to the strap or busbar.

Magnetism.—This is a property possessed by certain substances, and is manifested by the ability to attract and repel other materials susceptible to its effects. When this phenomena is manifested by à conductor or wire through which a current of electricity is flowing, it is termed “electro-magnetism.” Magnetism and electricity are closely related, each being capable of producing the other.

Magnetic Substances.—Only certain substances show magnetic properties, these being iron, nickel, cobalt and their alloys. The earliest known substance possessing magnetic properties was a stone or iron ore first found in Asia Minor. It was called the “lodestone, or leading stone, because of its tendency, if arranged so it could move freely, of pointing one particular portion toward the north.

Magnetic Attraction.-If the north pole of one magnet is brought near the south pole of another, a strong attraction will exist between them, this depending upon the size of the magnets used and the air-gap separating the poles. Magnets will attract all magnetic substances.

Magnetic Repulsion.-If the south pole of one magnet is brought close to the end of the same polarity of the other there will be a pronounced repulsion of the forces. The like poles of magnets will repel each other because of the obvious impossibility of uniting two influences or forces of practically equal strength but flowing in opposite directions. The unlike poles of magnets attract each other because the force is flowing in the same direction.

Magnetic Flow.—The flow of magnetism is through the magnet from south to north, and the circuit is completed by the flow of magnetic influence through the air-gap or metal armature bridging it from the north to the south pole.

Maximum Gravity.—The highest specific gravity which the electrolyte will reach by continued charging, indicating that no acid remains with the plates.

Meters.—Most of the electrical measuring instruments depend upon the principle of electro-magnetism or induction. These measuring instruments are made in portable and switchboard types. The windings in an instrument designed to measure current quantity or amperage are usually of coarse wires, while the windings of an instrument to measure electro-motive force or voltage will be of finer wire. The gauge used to measure current quantity is called an ampere meter or ammeter, while that used to measure current pressure is a volt meter.

Mica.-An insulator of natural mineral derivation that will stand considerable heat. Not suited for use with high-potential currents, because it is apt to contain impurities of a metallic nature. Commonly known as “isinglass.

Motor.-A machine that is capable of delivering current in one direction when driven by mechanical power and which will produce mechanical energy if electric current is passed through the winding in a reverse direction.

Motor-Generator.–An electrical machine that may be used either as a current producer or for generating electricity if driven by mechanical means, or as a power producer if driven by electrical means.

Negative Pole.—The terminal of a current-generator to which the current flows after leaving the outer circuit.

Nickel.--A silver white malleable and ductile metal, that can be applied to others by thin surface coating through an electro-deposition or plating process.

Nickel-Hydrate. A green powder used as the active material in the positive plates of the Edison storage battery.

Ohm.—The ohm is the unit by which resistance is judged. Everything has electrical resistance. Some elements have very little, such as

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