A dictionary of electrical words

Preface

The rapid growth of electrical science, and the almost daily addition to it of new words, terms and phrases, coined, as they too frequently are, in ignorance of those already existing, have led to the production of an electrical vocabulary that is already bewildering in its extent. This multiplicity of words is extremely discouraging to the student, and acts as a serious obstacle to a general dissemination of electrical knowledge, for the following reasons :

1. Because, in general, these new terms are not to be found even in the unabridged editions of dictionaries.

2. The books or magazines, in which they were first proposed, are either inaccessible to the ordinary reader, or, if accessible, are often written in phraseology unintelligible except to the expert.

3. The same terms are used by different writers in conflicting senses.

4. The same terms are used with entirely different meanings.

5. Nearly all the explanations in the technical dictionaries are extremely brief as regards the words, terms and phrases of the rapidly growing and comparatively new science of electricity.

In this era of extended newspaper and periodical publication, new words are often coined, although others,

II PREFACE.

already in existence, are far better suited to express the same ideas. The new terms are used for a while and then abandoned; or, if retained, having been imperfectlydefined, their exact meaning is capable of no little ambiguity ; and, subsequently, they are often unfortunately adopted by different writers with such varying shades of meaning, that it is difficult to understand their true and exact significance.

Then again, old terms buried away many decades ago< and long since forgotten, are dug up and presented in such new garb that their creators would most certainly fail to recognize them.

It has been with a hope of removing these difficulties to some extent that the author has ventured to present this Dictionary of Electrical Words, Terms and Phrases to his brother electricians and the public generally.

He trusts that this dictionary will be of use to electricians, not only by showing the wonderful extent. and richness of the vocabulary of the science, but also by giving the general consensus of opinion as to the significance of its different words, terms or phrases. It is, however, to the general public, to whom it is not only a matter of interest but also one of necessity to fully understand the exact meaning of electrical literature, that the author believes the book will be of greatest value.

In order to leave no doubt concerning the precise meaning of the words, terms and phrases thus defined^ the following plan has been adopted of giving,

(1) A concise definition of the word, term or phrase*

PREFACE. Ill

(2) A brief statement of the principles of the science involved in the definition.

(3) Where possible and advisable, a cut of the apparatus described or employed in connection with the word, term or phrase defined.

It will be noticed that the second item of the plan makes the Dictionary approach to some extent the nature of an Encyclopedia. It differs, however, from an encyclopedia in its scope, as well as in the fact that its definitions in all cases are concise.

Considerable labor has been expended in the collection of the vocabulary, for which purpose electrical literature generally has been explored. In the alphabetical arrangement of the terms and phrases defined, much perplexity has arisen as to the proper catch-word under which to place them. It is believed that part of the difficulty in this respect has been avoided by the free use of cross-references.

In elucidating the exact meaning of terms by a brief statement of the principles of the science involved therein, the author has freely referred to standard text books on electricity, and to periodical literature generally. He is especially indebted to works or treatises by the following authors, viz.: S. P. Thompson, Larden, Cumming, Hering, Prescott, Ayrton, Ayrton and Perry, Pope, Lockwood, Sir Wm. Thomson, Fleming, Martin and Wetzler, Preece, Preece and Sivewright, Forbes, Maxwell, De Watteville, J. T. Sprague, Oulley, Mascart and Joubert, Schwendler, Fontaine, Noad, Smee, Depretz, De la Rive, Harris, Franklin, Cavallo, Grove, Hare, Daniell, Faraday and very many others.

IV PREFACE.

The author offers his Dictionary to his fellow electricians as a starting point only. He does not doubt that his book will be found to contain many inaccuracies, ambiguous statements, and possibly doubtful definitions. Pioneer work of this character must, almost of necessity, be marked by incompleteness. He, therefore, invites the friendly criticisms of electricians generally, as to errors of omission and commission, hoping in this way to be able finally to crystallize a complete vocabulary of electrical words, terms and phrases.

The author desires in conclusion to acknowledge his indebtedness to his friends, Mr. Carl Hering, Mr. Joseph Wetzler and Mr. T. C. Martin for critical examination of his proof sheets ; to Dr. GL Gr. Faught for examination of the proofs of the parts relating to the medical applications of electricity, and to Mr. C. E. Stump for valuable aid in the illustration of the book ; also to Mr. Geo. D. Fowle, Engineer of Signals of the Pennsylvania Railroad Company, for information concerning their System of Block Signaling, and to many others.

Central High School, Edwin J. Houston.

Philadelphia, Pa.

September, 1889.

A DICTIONARY

OF

TD

IK

Abscissas, Axis of-

— Ouc of the axes of co-ordinates used for determining the position of points in a curved line.

Thus the position of the point D, Fig. B 1, in the curved line O D R, is determined by the vertical distances D 1, and D 2, of such point from two straight lines AB, and AC, called the axes of co-ordinates. AC, is called the axis of abscissas, and AB, the axis of ordinates. A, the point where the lines may be considered as starting or originating, is called thepoint of origin. (See Co-ordinates, Axes of.)

Absolute.— Complete in itself.

The terms absolute and relative are used in electricity in the same sense as ordinarily.

Thus, a galvanometer is said to be calibrated absolutely when the exact current strengths required to produce given deflections are known ; or, in other words, when the absolute current, strengths are known ; it is said to be calibrated relatively when only the relative current strengths required to produce given deflections are known.

The word absolute, as applied to the units employed in electrical measurements, was introduced by Gauss to indicate the fact that the values of such units are independent both of the size of the instrument employed and of the value of gravity at the particular place whore the instrument is used.

The absolute units of length, mass, and time are more properly called the C. G. S. units, or the eenti metre-gramme-second units.

An absolute system of units based on the milligramme, millimetre, and second, was proposed by Weber, and was called the millimetre-milligramme-second units. It has been replaced by the C. G. S. units.

Absolute Calibration. — (See Calibration, Absolute.,

Absolute Galvanometer. — (See Galvanometer, Absolute.)

Absolute Units. — A term sometimes used to indicate the C. G. S. units, but now generally replaced by the term centimet re-gramme-second units, or, more briefly, the C. G. S. units.

Absolute Unit of Current. — A current of ten amperes. (See Ampere. Units, Practical.)

Absolute Unit of Electromotive Force.— The one hundred millionth of a volt. (See Volt. Units, Practical.)

Absolute Unit of Resistance.— The one thousand millionth of an ohm. (See Ohm. Units, Practical.)

Absolute Vacuum. — (See Vacuum, Absolute).

Absorption, Electric The apparent soaking of

an electric charge into the glass or other solid dielectric of a Leyden Jar or Condenser. (See Charge. Condenser.)

The capacity of a condenser, or its ability to hold an electric charge, varies with the time the condenser remains charged. Some of the charge acts as if it soaked into the solid dielectric, and this is the cause of the residual charge. (See Charge, Residual.) Therefore, when the condenser is discharged, loss electricity appears than was passed in; hence the term electric absorption.

Absorptive Power. — The property possessed by many solid bodies of taking in and condensing gases within their pores.

Carbon possesses marked absorptive powers. The absorption of gases in this manner by solid bodies is known technically as the occlusion of gases. (See Occlusion of Gases.)

One volume of charcoal, at ordinary temperatures and pressures, absorbs of

Ammonia 90 volumes

Hydrochloric Acid .85

Sulphur Dioxide .65 "

Hydrogen Sulphide 55 "

Nitrogen Monoxide 40 "

Carbonic Acid Cas 35 "

Ethylene 35

Carbon Monoxide 9.42 "

Oxygen 9.25 "

Nitrogen 6.50 "

Hydrogen 1.25 "

(Saussure.)

Acceleration. — The rate of change of velocity.

Acceleration is thus distinguished from velocity : velocity expresses in tune the rate-of-change of position, as a velocity of three metres per second ; acceleration expresses in time the rate-of-change of velocity, as an acceleration of one centimetre per second.

Since all matter is inert, and cannot change its condition of rest or motion without the application of some force, acceleration is necessarily due to some force outside of matter itself. A force may therefore be measured by the acceleration it causes in a given mass of matter.

Acceleration is termed positive when the velocity is increasing, and negative when it is decreasing.

Acceleration, Unit of That acceleration which will give to a body unit -velocity in unit-time ; as, for example, one centimetre per second.

Bodies falling' freely in a vacuum, and approximately so in air, acquire an acceleration which in Paris or London, at the end of a second, amounts to about 9S1 centimetres per second, or nearly 32.2 ft. per second, v

a — — , or in other words, the acceleration equals the ve-

T

locity divided by the time.

But, since the velocity equals the Distance, or the Length

L traversed in a unit of time, v = — .

T L

V T L

Therefore, a = — = = — , or, the acceleration equals the

T T T~ length, or the distance passed through, divided by the square of the time in seconds.

These formulae represent the Dimensions of Acceleration.

Accumulator, or Condenser.— A term often applied to an apparatus called a Leyden Jar or Condenser, which permits the collection from an electric source of a greater charge than it would otherwise be capable of giving.

The ability of the source to give an increased charge is due to the increased capacity of a plate or other conductor when placed near another plate or conductor. (See Condenser. Jar, Leyden.)

Accumulator, Storage or Secondary Cell. —

Two inert plates dipping into a liquid incapable of acting chemicalty on either of them until after the passage of an electric current, when they become capable of furnishing an independent electric current.

F

F hPc

B

\ X

"m

F A

F'

This use of the term accumulator is the one most commonly employed. (See Storage Cells or Accumulators.)

Accumulator.— A term sometimes applied to Sir Win. Thomson's Electric Current Accumulator.

The copper disc D, Fig-. 2, has freedom of rotation, on a horizontal axis at O, in a magnetic field, the lines of force of which, represented by the dotted lines in the drawing, pass down perpendicularly into the plane of the paper. Fig. 2.

If, now, a current from any source be passed in the direction A, O, B, C, A, through the circuit A, O, B, C, A, which is provided with spring- contacts at O, and A, the disc will rotate in the direction of the curved arrow. This motion is due to the current acting on that part of the disc which lies between the two contacts — A and O. This apparatus is known as Barlow's Wheel.

If, when no current is passing through the circuit, the disc be turned in the direction of the arrow, a current is set up in such a direction as would oppose the rotation of the disc. (See Lenzs Laic.)

If, however, the disc be turned in the opposite direction to that of the arrow, induction currents will as before be produced in the circuit. xVs this rotation of the disc tends to move the circuit O A, towards the parallel but oppositely directed circuit B 0, these two circuits, being parallel and in opposite directions tend to repel one another, and there will thus beset up induced currents that tend to oppose the motion of rotation, and the current of the circuit will therefore increase in strength. (Sec Electro-Dynamics). Should then a current be started in the circuit, and the original field be removed, the induction will be continued, and a current which, up to a certain extent, increases or accumulates, is maintained in the circuit during rotation of the disc. (Larden.)

Barlow's Wheel, when used in this manner, is known as Thomson's Electric Current Accumulator.

Accumulator, Water-Dropping An apparatus devised by Sir W. Thomson lor increasing- the difference of potential of an electric charge.

The tube X Y, Fig-. 3, connects with a reservoir of water which is maintained at the zero potential of the earth. The water b eseapes from the openings at G and D in small drops and falls on funnels provided, as shown, to receive the separate drops nd again discharge them.

The vessels A, A', and B, B', which are electrically connected as shown, are maintained at a certain small difference of potential, as indicated by the respective -f and — signs.

Under these circumstances, therefore, C and D, will be charged inductively with charges opposite to those of A and B, or with — and -f electricities respectively. As the drops of water fall on the funnels, the charges which the funnels thus constantly receive, are given up to B' and A', before the water escapes. Since, therefore, B, B', and A, A', are receiving- constant charges, the difference of potential between them must continually increase. This apparatus operates on the same principle as the replenisher. The drops of water act as the carriers, and A, A', and B, B', as the hollow vessels. (See Replenisher.)

Accumulators or Condensers ; L<aws of Accumulation of Electricity. — Sir W. Snow Harris, by the use of his Unit- Jar, and Electric Thermometer, deduced the following laws for the accumulation of electricity, which we quote f rora Noad's "Student's Text-Book of Electricity," revised by Preece :

(1) "Equal quantities of electricity are given off at each revolution of the plate of an electrical machine to an uncharged surface, or to a surface charged to any degree of saturation."

(2) "A coated surface receives equal quantities of electricity in equal times ; and the number of revolutions of the plate is a fair measure of the relative quantities of electricity, all other things remaining the same."

(3) "The free action of an electrical accumulation is estimated by the interval it can break through, and is directly proportional to the quantity of electricity."

(4) "The free action is inversely proportional to the surface."

(.")) " When the electricity and the surface are increased in the same ratio, the discharging interval remains the same; but if, as the electricity is increased, the surface is diminished, the discharging interval is directly as the square of the quantity of electricity."

(G) "The resistance of air to discharge is as the square of the density directly."

According to some later investigations, the quantity a plane surface can receive under a given density depends on the linear boundary of the surface as well as on the area of the surface.

"The amount of electrical charge depends on surface and linear extension conjointly. There exists in every plane surface what may be termed an electrical boundary, having an important relation to the grouping or disposition of the electric particles in regard to each other and to surrounding matter. This boundary in circles or globes is represented by their circumferences. In plane rectangular surfaces, it is by their linear extension or perimeter. If this boundary be constant, their electrical charge varies with the square root of the surface. If the surface be constant the charge varies with the square root of the boundary. If the surface and boundary both vary, the charge varies with the square root of the surface midtijilied into the square root of the boundary.'''

These laws apply especially to continuous surfaces taken as a whole, and not to surfaces divided into separate parts.

By electrical charge Harris meant the quantity sustained on a given surface under a given electrometer indication ; by electrical intensity, he meant the indication of the electrometer corresponding to a given quantity on a given surface. For further information see Condensers, Capacity of. A, C C — An abbreviation used in medical electricity for Anodic Closure Contraction, or the contraction observed on (losing the circuit when the anode is lying over the muscle.

The term anode is sometimes, as above, used to indicate the positive terminal of an electric battery or source. (See Anode.) Achromatic. — Free from false coloration. Images formed by ordinary lenses do not possess the true colors of the object, unless the edges of the lenses are cut off by the use of a diaphragm; i. e., an opaque plate with a circular central opening. The edges of the lenses disperse the light like an ordinary prism, and so produce rainbow-colored (prismatic) fringes in the image. The use of an achromatic lens is to obviate this false coloration.

The ray of light entering the prism ABC, Fig. 4, sutlers dispersion (separation into prismatic colors). This dispersion in the same medium is proportional to the angle g, between the incident and emergent faces, called the refracting angle.

If, now, another prism BCD, of the same material, whose refracting angle g', is equal to g, is combined with the first prism in the manner shown in Fig. 4, it will produce an equal but opposite dispersion, so that the ray of light will emerge at E, free from rained bow tints, but parallel to its origi- *%' k ' nal direction.

B

D mmsmiiiii

ZiX

Glass / „

:VW

Oown

Glass

•1/

WORDS, TERMS AND PHRASES.

The variety of glass called crown glass produces only half as great dispersion of light as the variety called flint glass, under the same refracting angle g. If the prism A B C, of crown glass, Fig. 5, whose angle g, is twice as great as the refracting angle g', of the prism BCD, of flint glass, he connected with it in the manner shown, then the ray R, will he transmitted free from color, but will not emerge parallel to its original direction ; in other $% g , ,5.

words, it suffers refraction or bending. (See Refraction.)

The construction of achromatic lenses is based on this principle.

Fig. G.

The crown glass is generally made with two convex surfaces ; the flint glass, with one concave and one plane surface, as shown in Fig. 6.

Sometimes both surfaces of the flint glass are made curved, as in Fisr. 7.

Fig. 7.

Aclinic Line. — The magnetic equator, or a line on the earth's surface connecting places where the magnetic needle has no inclination or dip.

The magnetic equator is not a circle, It cuts the geographical equator at 2° E. long., and at 170° W. long. (See Inclination Map or Chart.)

Acoustic Engraving.— (See Engraving, Acoustic.)

Acoustic Telegraph.— A non-recording system of telegraphic communication, in which the dots and dashes of the Morse system, or the deflections of the needle in the needle system, are replaced hy sounds that follow one another at intervals that represent the dots and dashes, or the deflections of the needle, and thereby the letters of the alphabet.

Steinheil and Blight each invented acoustic systems of telegraphy in which electro-magnetic bells are used. Morse invented a Sounder, for this purpose, which is used very generally. (See Sounder, Telegraphic.)

For details of the apparatus and system see Telegraphy, American or Morse system of.

Actinic Photometer.— (See Photometer, Actinic.)

Actinic Kay*. — The rays of light, or other forms of radiant energy that possess the power of effecting chemical decomposition. (See Decomposition.)

All rays of light, and even some of those invisible to the human e3'e, are actinic to some particular chemical substance or another. Whether the ether waves produce the effects of heat, light, or chemical decomposition depends on the nature of the material on which they fall, as ivell as on the character of the waves themselves.

Actinism. — The chemical effects of light, as manifested in the decomposition of various substances.

Under the influence of the sun's light, the carbonic acid absorbed by the leaves of plants is decomposed in the living leaf into carbon, which is retained by the plant for the formation of its woody fibre or ligneous tissue, and oxygen, which is thrown off.

The bleaching of curtains, carpets, and other fabrics exposed to sunlight is caused by the actinic power of the light. The photographic picture is impressed by the actinic power of light on a plate covered with some sensitive metallic salt, generally silver.

Action, Local An irregular dissolving or consumption of the zinc or positive element of a voltaic battery, by the fluid or electrolyte, when the circuit is open or broken, as well as when closed, or in regular action.

Local action is due to impurities, such as carbon, iron, arsenic, etc., in the positive plate. These impurities form with the positive element little voltaic couples, and thus direct the corrosive action of the liquid to portions of the plate near the impurities. Local action causes a waste of energy. It may be avoided by amalgamation of the zinc. (See Zinc, Amalgamation of.)

Action, Local A term proposed, but not generally adopted, to indicate the wasteful currents in the pole pieces or cores of dynamo-electric machines.

These cm-rents are now generally known as Eddy, Foacaidt, or Parasitical Currents. (See Car rents, Eddy, Foacaidt, Local, or Parasitical.)

Action, Ulagnc-Crystallic (See Magne-Crystal-

lie Action.)

Action, Unit of A rate of working, which will

perform one unit of work per second.

In C. G. S. units, the activity of one erg per second. This unit is very small. One Watt, the practical unit of power, is equal to ten million ergs per second. (See Watt.)

The unit of activity generally used for mechanical power is one horse-power, or 746 watts. (See Horse-power.)

Activity. — The work done per second by any agent.

Work-per-second, or, as generally termed in the United States, Power, or Rate of Doing Work. (See Power.)

A. I>. C. — An abbreviation used in medical electricity for Anodic Duration Contraction.

Adhesion. — The attraction that exists between unlike molecules. (See Attraction, Molecular.)

A substance is said to be diathermanous when it is transparent to heat. Clear, colorless crystals of rock salt are very transparent both to light and to heat. Rock salt, covered with a layer or deposit of lamp-black or soot, is quite transparent to heat. An adiathermanous body is one which is opaque to heat.

Heat transparency varies not only with different substances, but also with the nature of the source from which the heat is derived. Thus, a substance may be opaque to the heat from a non-luminous source, such as a vessel filled with boiling- water, while it is comparatively transparent to that from a luminous source, such as an incandescent solid, or the voltaic arc.

A similar difference exists as regards transparency to light. A colorless glass will allow light of any color to pass through it. A blue glass will allow blue light to pass freely through it, but will completely prevent the passage of any red light ; and so with other colors.

T]|»iiiu*' Condenser. — (See Condenser.)

Affinity, < iieinieal Atomic attractions.

The force that causes atoms to unite and form chemical molecules.

Atomic, or chemical attraction generally results in a loss of the characteristic qualities, or properties, that distinguish one kind of matter from another. In this respect it differs from adhesion, or the force which holds unlike molecules together. (See Adhesion.) If, for example, sulphur is mixed with lamp-black, no matter how intimate the mixture, the separate particles, Avhen examined by a glass, exhibit their peculiar color, lustre, etc. If, howerer, the sulphur is chemically united with the carbon, a colorless, transparent, mobile liquid, called carbon bisulphide, results, that possesses a disagreeable, penetrating odor.

Chemical affinity, or atomic combination, is influenced by a variety of causes, viz. ;

(1) Cohesion. Cohesion, by binding- the molecules more firmly tog-ether, opposes their mutual atomic attractions.

A solid rod of iron will not readily burn in the flame of an ordinary lamp, but if the cohesion be overcome by reducing the iron rod to filings, it burns with brilliant scintillations when dropped into the same flame.

(2) Solution. Solution, by imparting to the molecules greater freedom of motion, favors their chemical combination.

(3) Heat. Heat favors atomic combination by decreasing the cohesion, and possibly, by altering the electrical relations of the atoms. If too great, heat may produce decomposition. (See Dissociation.)

(4) Light. Decomposition, or the lessening of chemical affinity through the agency of light, is called Actinism. Light also causes the direct combination of substances. A mixture of equal volumes of hydrogen and chlorine unites explosively when exposed to the action of full sunlight. (See Actinism.)

(5) Electricity. An electric spark will cause an explosive combination of a mixture of oxygen and hydrogen. Electricity also produces chemical decomposition. (See Electrolysis.)

AgOlie. — A line connecting places on the earth's surface where the magnetic needle points to the true geographical north.

The line of no declination or variat ion of a magnetic needle. (See Declination or Variation of Magnetic Needle.)

As all the places on the earth where the magnetic needle points to the true north may be arranged on a few lines, it will be understood that the pointing of the magnetic needle to the true geographical north is the exception and not the rule. In many places, however, the deviation from the true geographical north is so small that thue direction of the needle may be regarded as approximately due north.

Air-Bla§t.— An invention of Prof. Elihu Thomson to prevent the injurious action of destructive sparking at the commutator of a dynamo-electric machine.

A thin, forcible blast of air is delivered through suitable tubes at points on the three-part commutator cylinder of the Thomson Houston dynamo, where the collecting- brushes bear on its surface. The effect is to blow out the arc and thus prevent lis destructive action on the commutator segments. The use of the air-blast also permits the free application of oil. thus further avoiding wear.

The blast-nozzles are shown at B 3 , B 3 , Fig. 8, near the collecting brushes.

The air-supply is obtained from a centrifugal blower attached directly to the shaft of the machine. Its construction and operation will be readily understood from an inspection of Fig. 9, in which the top is removed for a ready examination of the interior parts.

Fig, 0.

Alarms, Electric Various automatic devices by

which attention is called to the occurrence of certain events, such as the opening of a door or window; the stepping of a person on a mat or staircase ; the rise or fall of temperature bej^ond a given predetermined point ; or to call a person to a telegraphic or telephonic instrument.

WORDS, TERMS AND PHRASES.

Electric alarms arc operated by either the closing or the opening of an electric circuit, generally the former, by means of which an electro-magnetic or

Electric alarms may be divided into two classes, viz. :

1. Mechanically operated alarms, or those operated by clock-work, that is started by means of an electric current.

2. Those in which the alarm is both set into operation and operated by the action of an electric current.

In Fig. 10, is shown the general construction of an electrically started mechanical alarm. The attraction of the armature B, by the electromagnet A, moves the armature lever pivoted at C, and thus releases the catch e, and permits the spring or weight connected with the strike the bell.

Electrically actuated alarm-bells automatic make-and-break form, operated by the attraction of the mechanical bell is rum

itlF 1

Fig. 10. clock movement to set it in motion and are generally of the The striking lever is armature of an electromagnet, and is provided with a contact-point, so placed that when the hammer is drawn away from the bell, on the electro-magnet losing its magnetism, the contact-point is closed, but when it is drawn towards the bell the contact is opened. When, therefore, the hammer strikes the bell, the circuit is opened, and the electro-magnet releases its armature, permitting a spring to again close the contact by moving the striking lever away from the bell. Once set into action, these movements are repeated while there is battery power sufficient to energize the magnet. T

In Fig. 11, the

battery terminals

are connected with the right and left hand binding-posts, P and M.

The hammer K, is connected with a striking lever, which forms part of the circuit, and which is attached to the armature o f the electro- Fig. n. magnet e. A me-

tallic spring g, bears against the armature when the latter is away from the magnet, but does not touch the armature when it is moved towards the magnet. The movements of the armature thus automatically open and close the circuit of the electro-magnet.

This form of make-and-break is called an automatic make-and-break.

Alarms, Electric Burglar

An electric device

to automatically announce the opening of a door, window, closet, drawer, or safe, or the passage of a person through a hallway, or on a stairway.

Electric burglar alarm devices generally consist in mechanism for the operation of an automatic make-and-break bell on the closing of an electric circuit. The bell may either continue ringing only while the contact remains closed, or, may, by the throwing on of a local circuit or battery, continue ringing until stopped by some non-automatic device, such as a hand-switch.