Henry and Hora's modern electricity; a practical working encyclopedia

Front matter

HENRYandHGRA'S m*

MODERN Yt ELECTRICITY I

50 Illustrations / a m, m t ;

Index

Accumulator, 39.

Alternate currents — cfiemical effect, 159.

measurement, 160.

pressure of, 150.

Alternating currents, 103, 162.

machines, 149.

Alternators, 169.

— armature of, 174.

— coupling, of, 175.

— field excitation, 172. magnets, 172.

Aluminum, reduction of, 296.

Ampere turns, 142.

Angle of lag, 154.

Appendix. 347.

Arc— Voltaic, 228.

Armature, 128.

— winding, 140.

Arrester — lightning, 195.

Automatic self-regulation, 166.

Batteries, 32.

— cell arrangement, 45.

— Edison, 43=

— secondary, 39, 44.

— storage, 42.

Bells— electric, 220.

— magneto, 225.

Booster, The, 169.

Box— starting, 195.

Brilliancy of arc, 229.

Brushes, 139.

Buildings, wiring of, 219.

Cables — submarine, 257.

Calculation— ampere turns, 142.

Calcium carbide, 298.

Candle-foot, 246.

Candle power, 231.

Carbon, 231.

Carborundum, 298.

Cells — arrangement of, 45.

— constants, 38.

— gravity, 37.

— storage, 40.

Central exchange, 266.

Chemical effect— alternate current, 150.

— equivalents, 51, 52, 53.

— symbols, 354.

Choking coils, 159.

Circuits, 62, 237.

— breaker, 192.

— magnetic, 130.

— opened and closed, 253.

— polyphase, 177.

Cleaning solutions, 293.

Coefficient —of self-induction, 156.

Coherer, 280.

Coil — choking, 159.

— induction, 104.

Compound wound dynamo, 138.

Condenser— arrangement of, 122.

— electrical capacity, 28, 120.

— testing, 123.

Conductance, 59.

Conductors and non-conductors, 19.

— table of, 19.

Connections for lamps. 243.

Controller, 199.

Copper equivalents of steel rails, 352.

— plating, 291.

— refining, 294.

Corrosion of pipes, 347.

Crookes tubes, 302.

Current— alternating, 103, 162.

Vll

Vlll

INDEX

Current and pressure, 295.

— effective, 159.

— polyphase, 176.

— pressure curve, 150.

— thermo-electric, 75.

— for plating, 292.

Cut-outs, 194.

Depolarization— chemical, 35.

— electro-chemical, 36.

— mechanical, 34.

Detector— ground, 226.

— lineman's, 225.

Diplex telegraphy, 256.

Distribution, 203.

Drop in mains, 243.

Duplex telegraphy, 254.

— series, shunt, compound wound, 137.

— Siemen's, 173.

Efficiency of a motor, 144, 351.

— of dynamos, 351.

Electric arc, 234.

— heating, 300.

— light and power transmission, 330.

— meters, 108.

— smelting, 297.

— welding, 298.

Electrical energy, 23.

— discharges, 301.

— engineering, 314.

— lighting, 228.

— machines, 23.

Electricity, 15.

— Production of, 16; static and cur rent, 17; positive and negative, 18; conductors and non-conductors, 19; induction, 20; energy, 23, 70.

Electrodynamometer, 113.

Electrolysis, 50, 289, 347.

Electromagnet, 89.

Electromagnetic inertia, 152.

— disturbance, 277.

Electromagnetic induction, 100.

Electromagnetism, 85.

Electrometer, 112.

Electro-metallurgy, 289.

Electroplating, 289, 293.

Electrotyping, 294.

Electrolytic refining, 294.

Electroscope, 21.

Equivalents, 51, 52, 53.

Estimates on electric railways, 324, 346. Ether, 274, 277.

Fall of potential, 67.

Faraday's laws, 53.

Faults— in lines, 253.

machines, 185.

wires, 221.

Field magnets of alternators, 172.

Filaments, 238.

Friction machine, 24.

Galvanometer, 110.

Gold plating, 292.

Ground detector, 226.

Hot-wire instruments, 117.

Hydraulic analogy, 26, 149.

Induced pressure, 101.

Induction, 20.

— electro: uagnetic, 100.

— magnetic, SI.

coefficient of, 156.

Inductive capacity, 124.

Impedance, 156.

Instruments— hot-wire, 117.

— Morse, 249.

Insulation, 211.

Joule's law, 72.

Jack, The, 267.

Key— telegraph, 250.

Lag— angle of, 154.

INDEX

IX

Lamps, 232.

— incandescent, 237.

base and socket, 240.

connections, 243.

fiiament, 238.

principle, 238.

rating of, 243.

life of, 241.

— mercury vapor. 244.

Lenz's law, 105.

Lighting, electric, 228.

Lightning, arrester, 195.

Line faults in, 253.

— telegraph, 252.

— testing, 222.

Lineman's detector, 225.

Locating a ground, 224.

Location of transformers, 167.

Machines— alternating current, 149.

— classification, 133.

— faults in, 185.

— friction, 24.

Magnetic circuit, 130.

— induction, 81.

— field, 83.

— substance, 82.

Magnetism, 80.

— measure of, 84.

Magneto-bells, 225, 264.

— generator, 264.

Magnetomotive force, 93.

Marconi's telegraph, 284.

Material for electric railway, 322.

Measuring alternate current, 160.

Measurements, 107, 245.

Mercury vapor lamps, 244.

Meters, 107; voltameter, 54, 109: voltmeter. 118; galvanometer, 110; wattmeter, 118; electrometer, 112; electrodynamometer, 113.

Metric system, 352.

— equivalents, 353.

Microphones, 263.

Morse alphabet, 249.

— instrument, 249.

— efficiency. 144.

— induction, 178.

Multiplex telegraphy, 254.

Nickel plating, 291.

Ohm's law, 58.

Overhead wires, 213.

Permeability, 90.

Plating, 292.

Plug, The, 267.

Polarization, 34.

Polarized relay, 255.

Polyphase circuits 177.

— currents, 176.

Potential, 23, 67.

Power stations, 185, 327 .

Practical points, 186.

— for plating, 292.

Radium, 301, 311, 313.

Radiographs, 308.

Rail welding, 299.

Railway curves, 326-7.

Rating of lamps, 242.

Receiver, 261.

Refining copper, 294.

— silver, 296.

Reduction of aluminum, 296.

Recording register, 251.

Regulating mechanism, 233.

Relay, The, 252.

— Polarized, 255.

Resistance, 60, 62.

— insulation, 116.

— of wire, 61.

Rheostat, 113.

Roentgen's rays, 302.

Saturation curve, 91.

Secondary battery, 39.

Self-induction, 105, 152.

INDEX

Series wound dynamo, 137.

Shunt wound dynamo, 138.

Silver plating, 289.

— refining, 296.

Siemens' dynamo, 173.

Sine curve, 150.

Solenoid, 87.

Specific inductive capacity, 124.

Standard of resistance, 60.

Starting box, 195.

Storage battery, 42.

Submarine cables, 257.

Subscriber's sets, 265.

Switches, 193.

Telegraph, The, 248.

Telegraphy— automatic and autographic, 256.

— diplex, 256.

— duplex, 254.

— multiplex, 254.

Telephone, The, 258.

— common battery system, 271.

— automatic system, 272.

— induction coil, 264.

— switchboard, 266, 269.

Temperature and brilliancy of arc, 229. • — co-efficient, 60.

Terrestrial magnetism, 81.

Testing condenser, 123.

Thermo-electric current, 75.

Three-wire system, 204, 355.

Torque, 144.

Transformers, 164.

Transmission and distribution, 203, 330.

Transmitter, 261.

Trolley, 198.

Tubes, constancy of, 310.

— life of, 309.

Two-wire system, 203.

Undergiound wires, 214.

Units of work and power, 68.

— table of electrical. 107.

Vacuum, 240,301.

Vat, 290.

Vibrations, 275.

Voltaic arc, 228.

— pile, 32.

Voltameter, 109.

— water, 54.

Water voltameter, 54.

Wattmeter. 118.

Weight and capacity of cars, 326

Welding electric, 298.

Wheatstone's bridge, 114.

Wire, the, 206.

— carrying capacity, 209.

— faults in, 221.

— overhead, 213,

— properties of, 208.

— underground, 214.

Wiring buildings, 219.

Wireless telegraphy, 281, 284, 28&

Zinc, 38.

THOMAS A. EDISON

THE WORLD'S GREATEST ELECTRICIAN

CHAPTER I. — Introduction Electricity

i. The true nature of electricity has not yet been discovered. Many think it a quality, inherent in nearly all the substances, and accompanied by a peculiar movement or arrangement of the molecules. Some assume that the phenomena of electricity are due to a peculiar state of strain or tension in the ether which is present everywhere, even in and between the atoms of the most solid bodies. If the latter theory should be the true one, and if the atmosphere of the earth is surrounded by the same ether, it may be possible to establish these assumptions as facts. The most modern supposition regarding this matter, by Maxwell*, is that light itself is founded on electricity, and that light waves are merely electro-magnetic waves. The theory " that electricity is related to, or identical with, the luminiferous ether," has been accepted by the most prominent scientists.

But while electricity is still a mystery, much is known about the laws governing its phenomena. Man has mastered this mighty force and made it his powerful servant ; he can produce it and use it.

*James Clerk-Maxwell, a celebrated Scotch physicist (I831-1879), first called attention to the fact, that the velocity of light waves (185.000 miles per second) and of electricity seem identical. Experiments made since, chiefly by Hertz, have demonstrated that electric waves have all the properties of light waves. They can be reflected, refracted, polarized, brought to a focus, etc.

2. Its simplest effects were observed by the ancient Greeks. Thales of Miletus, who flourished about 600 B. C, noticed that amber, when rubbed with silk, attracted light bodies, as bits of bran or cork. The name "electricity" is derived from elektron, the Greek for amber. The word was first used in 1600, by Dr. Gilbert, a famous English scientist, who proved before a large assembly in Colchester, that diamonds, crystals of minerals, glass, and sealing wax, had the same peculiarity as amber. He also mentioned the fact that moist air prevented good results in his experiments. The phenomena of electricity are attraction and repulsion, heat, light, mechanical destruction, and chemical decomposition. They have been known In part for considerable periods, but all their practical applications are of recent origin.

Production of electricity

3. Electricity is generated by mechanical or chemical action

(a) Friction. (See § 5.)

(b) Percussion. A blow by one substance on another produces opposite electrification on the two surfaces that come in contact.

(c) Vibration. Vibration produced in a rod of iron coated with an insulating substance produces opposite electricities (in the rod and the coating). Experiments made by Volpicelli.

(d) Disruption. If a playing card is torn in two pieces, both pieces prove to be electrical.

(e) Cleavage. Quick cleavage of mica produces sparks in a dark room.

(f) Crystallization. Sulphur melted by heat and then left to cool and crystallize, becomes electrified when in process of crystallization.

ELECTRICAL ENGINEERING \*J

(g) Evaporation. When water evaporates, the liquid possesses the opposite electrification of the vapor.

(h) Combustion. Burning charcoal proves to be electrified.

(I) Pressure. Cork when pressed with guttapercha or metals proves to be + (plus) electrified, while the guttapercha or metals are — (minus) electrified.

(j) Heating of crystals. Tourmaline and other crystals, when heated or cooled, become electrified. (Such crystals are called pyro-electric.)

(k) Atmosphere. The atmosphere is always charged with more or less electricity.

(1) Some animals are provided with an electric organ which they bring into action when touched by an enemy. Torpedo, gymnotus, and malapterurus are fish possesing powerful electric organs.

(m) The roots and juice of plants are — , the leaves +•

(n) Dissimilar metals when brought into contact produce opposite electrification.

(o) Heating the junctions of two dissimilar metal rods produces opposite electrification in them, and electricity flows from one metal rod across the junction to the other.

(p) Contact of two dissimilar liquids.

(q) Contact of a liquid and a metal.

(r) Chemical action of a liquid on two dissimilar metals,

(s) Movement of a conductor in a magnetic field {magnetoelectricity.}

Static and current electricity

4. There are two states of electricity, static and current. The first is electricity at rest, the second is electricity in motion. The difference between them is not well defined, and the laws governing the two kinds are about the same. Static electricity includes the facts known to the ancients. There is, however, one important difference : Current electricity seems to flow through the substance of the conductor; Static electricity remains always on the surface of the charged body, as, for instance, in a hollow cylinder it is found on the outside or convex surface. The reason for this difference is unknown, but it is probably closely connected with the nature of the two kinds of electricity.

Positive and negative electricity

5. A glass rod rubbed with silk in dry air, becomes charged with an electricity called positive, while a rod of sealing-wax or other resinous substance, rubbed with wool or fur produces an electricity called negative. These terms were first employed by Benj. Franklin, instead of the old names vitreous and resinous electricity. That this distinction is not made without a difference, can be proved in the following manner:

Two balls of light material, as pith, are attracted to a charged glass rod, adhere to it, become charged themselves and then are repelled and fly off. They also repel each other, when charged and suspended in close proximity, but are attracted by a charged rod of sealing-wax.

From these facts the following general law is deduced :

RULE 1 . — A body charged with one kind of electricity repels one charged with the same kind, and attracts one charged with the opposite kind.

6. The silk and wool, with which the rods were rubbed are affected in the reversed sense ; the silk used to rub the glass is found to be negatively electrified, and the wool with which the sealing-wax was rubbed is found to be positively excited. From this fact we deduce another general rule :

- RULE 2. — Whenever a positive charge is developed, an equal negative charge is also developed and vice versa.

7. But silk does not produce positive electricity in all other substances; sulphur, for instance, becomes negatively charged if rubbed with silk. In the following series, materials are enumerated in such an order that by rubbing together any two materials named, the one mentioned first will generally become positively charged : fur, wool, certain resinous substances, glass, cotton, silk, wood, metals, sulphur, certain other resinous substances, India-rubber, hard rubber.

Conductors and non=conductors

8. Metals become electrified by mere rubbing, but if the piece of metal is held in the hand while rubbing it, the electricity flows into the human body as fast as it is produced. This can be avoided by fastening the metal in a frame or handle of dry wood or hard rubber. Materials which allow electricity to flow through them, or in other words, which conduct electricity, are called conductors ; materials that conduct electricity only slightly or not at all, are termed non-conductors Or INSULATORS.

TABLE OF CONDUCTORS.

GOOD.

PARTIAL.

NON-CONDUCTORS.

I. 3- 4- silver (best)

metals

charcoal

graphite

acids

salty solutions

water

8. animal bodies

9. plants

10. cotton

1 1 . dry wood

12. marble

13. paper

14. oil

15. porcelain

16. silk

17. wool

18. resin

19. shellac

20. sulphur

21. ebonite

22. paraffine

23. glass

24. dry gases

25. air

Dry air is a perfect or absolute insulator or isolator.

9. A conductor is said to be insulated, when it is supported on insulators in such a way that electricity cannot flow or escape from it, — as by placing it on a plate of glass, or on feet of glass or other insulating material,

Induction

10. If two bodies, as brass balls, both insulated, and one electrified, the ether not, are placed near together, the other will also be found to become electrically charged, by induction. The side near the first ball will hold the opposite kind, and the other side will show the same kind of electricity as the first ball holds. If a finger is held close to the further side of the second ball, the electricity on that side passes into the body of the person, leaving the ball charged with the opposite kind of electricity. This charge will spread over the whole ball, if it is removed from the neighborhood of the first ball. If, however, the two balls are brought into contact, the two charges will join, balancing, and thereby destroying, each other. This proves that the two charges, the inducing one and the induced one, are equal to each other.

ii. It can be proved, furthermore, that the attraction of light bodies, as pith balls, by charged bodies, is caused by induction. The glass rod or sealing-wax first charges the pith ball by induction, half positively, half negatively. One half is attracted, the other half is repelled. The attracted half is nearer the inducing body than the repelled half, and, therefore, the force of attraction is greater than that of repulsion.

12. The unit of quantity of electricity is the coulomb, named after a French physicist who lived 1736-1806. Each coulomb in one charged body attracts or repels each coulomb in the other. Therefore:

RULE 3. — The total attraction or repulsion is equal to the number of coulombs in one multiplied by the number in the other,

The intensity of attraction or repulsion between two charged bodies, then, is determined, first, by the product of the quantities of electricity in the two bodies ; second, by the material between them ; and third, by the distance between them.

The electrostatic unit of quantity is the quantity which, when placed at a distance of one centimeter in air from an equal quantity, repels it with a force of one dyne.

Two spheres charged with 4 and 6 units respectively are placed 2 centimeters apart. What force will they exert on each other?

Solution :

Any result equals the force divided by the resistance. The force is 4 multiplied by 6 ; therefore the resistance must be 2 multiplied by itself.

2^2 = 6 dynes. Ans

Electroscope

13. An electroscope is used to discover the presence of a charge ; an electrometer measures the quantity of electricity in a charge. An electroscope is necessarily a very sensitive instrument. The one shown in fig. 1 consists of a glass jar, through the stopper of which a FlG> L

brass rod extends into the interior of the jar. At the lower end of the brass rod two narrow strips of gold leaf are attached.

m

hanging straight down. As soon as any body, as a stick of sealing-wax, charged in the slightest way, is brought near the upper end of the brass rod, the two strips of gold leaf will fly apart, and if the charge is strong they will tear. This is caused by induction: the upper end of the brass rod becomes charged positively at the approach of the negatively charged sealing-wax, and consequently the two pieces of gold leaf are charged negatively and repel each other.

Q. Name a few common manifestations of electricity?

A. When the air is dry and hair is combed with a rubber or metal comb, the hairs rise toward the comb and are repelled by each other. A faint crackling noise is heard, and If it is dark, minute sparks may be seen. Dragging the feet quickly over a woolen carpet and then approaching a conducting body with a finger, a spark will show, which in some instances has been utilized to light the gas. The lightning in the clouds is such a spark of enormous size and length.

Q. How do like charges of electricity affect each other?

A. They repel each other.

Q. What efect have unlike charges of electricity upon each other ?

A. They attract each other.

Q. If metal is rubbed with silk, with what kind of electricity will it be charged?

A. The metal negative, and the silk positive.

Q. If metal is rubbed with India-rubber, with what kind of electricity will it be charged ?

A. The metal positive, and the India-rubber negative.