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[Illustration]
[Illustration]
THE THOUGHT IS IN THE QUESTION THE INFORMATION IS IN THE ANSWER
HAWKINS
ELECTRICAL GUIDE
NUMBER
ONE
QUESTIONS
ANSWERS
&
ILLUSTRATIONS
A PROGRESSIVE COURSE OF STUDY
FOR ENGINEERS, ELECTRICIANS, STUDENTS
AND THOSE DESIRING TO ACQUIRE A
WORKING KNOWLEDGE OF
ELECTRICITY AND ITS APPLICATIONS
A PRACTICAL TREATISE
by
HAWKINS AND STAFF
THEO. AUDEL & CO. 72 FIFTH AVE. NEW YORK.
COPYRIGHTED, 1914,
BY
THEO. AUDEL & CO.,
NEW YORK.
Printed in the United States.
PREFACE
_The word “guide” is defined as:_
=_One who leads another in any path or direction; a person who shows or
points out the way, especially by accompanying or going before; more
particularly, one who shows strangers or tourists about; a conductor;
leader, as “let us follow our guide.”_=
_This book, or =“Guide,”= is so called because it =leads= or =points out
the way= to the acquirement of a theoretical and practical knowledge of
Electricity._
_There are several guides, each covering in detail a certain phase of the
broad subject of Electricity and leading the reader progressively, and in
such a way, that he easily grasps, not only the simple fundamental facts,
but the more complex problems, encountered in the study of Electricity.
This is accomplished by the aid of a =very large number of illustrations=,
together with specific explanations, worded in =concise and simple
language=._
_The Guides are written partly in the question and answer form, as this
style of presentation has met with hearty approval, not only from those of
limited education, but also from the better informed._
_Where recourse is had to the question and answer form, the special aim of
the author has been to give short and direct answers, in such plain
language as to preclude a misconception of the meaning. With this in view,
=the answer gives= simply =the information sought by the question=._
_=The answer is limited to one paragraph= so that the reader may
concentrate upon the fact or facts demanded by the question._
_Any enlargement of the answer or specific explanations of items contained
therein, are presented in separate paragraphs printed, in smaller type._
_With this plan of =separating the answer=, as it were, from items of
secondary importance, and making it short and simple, its content is more
forcibly impressed upon the mind of the reader._
_In a text book, it is necessary to illustrate and explain the various
species of commercial apparatus met with in practice, and in this
connection the Publishers desire to call attention to the manner in which
the author has treated what may be classed as the =“descriptive matter.”=
Contrary to the usual custom of giving descriptions of commercial machines
in the main text, where they would occupy considerable space, to the
exclusion of the more important matter, all such descriptions are placed
in small type directly under the illustrations, leaving space for an
adequate presentation of the underlying =principles=, =theories=, and for
the large amount of =practical information= that is essential to obtain a
general knowledge of Electricity and its numerous applications._
_Credit is largely due to Frank D. Graham, B.S., M.S. (Princeton
University), and M.E. (Stevens Institute), practical engineer, for the
authorship of the =Guides=, and for original sketches illustrating
electrical principles and construction._
TABLE OF CONTENTS GUIDE NO. 1.
=INTRODUCTORY CHAPTER=
=SIGNS AND SYMBOLS=
=ELECTRICITY= =1 to 4=
Nature and source--=kinds of electricity:= static, current,
dynamic, radiated, positive, negative, atmospheric, frictional,
resinous, vitreous.
=STATIC ELECTRICITY= =5 to 26=
Electrical =attraction and repulsion=--the charge--distribution
of the charge--free and bound electricity--conductors and
insulators--=electroscopes=--gold leaf electroscope--electric
screens--electrification by induction--nature of the induced
charge--the electrophorus--=condensers=; Leyden jar--=electric
machines=--action of Toepler-Holtz machine--Wimshurst machines.
=THE ELECTRIC CURRENT= =27 to 34=
Volt--ampere--ohm--=Ohm’s law=--production of the electric
current--current strength--voltage drop in an electric current.
=PRIMARY CELLS= =35 to 67=
=The word “battery”=--action of cell--chemical changes;
polarization--effects of polarization--methods of depolarization--
depolarizers--depolarizer bag--Volta’s contact law--contact
series of metals--=laws of chemical action in cell=--
requirements of a good cell--=single and two fluid cells=--
the Leclanche cell--Fuller bichromate cell--the Edison
cell--Grenet bichromate cell--Daniell cell--directions for
making a Daniell cell--gravity cells--Daniell gravity
cell--so-called “dry” cells--=points relating to dry cells=--
care of cells--cleanliness--separating the elements--creeping--
amalgamated zinc--battery connections.
=CONDUCTORS AND INSULATORS= =68 to 74=
The so-called “non-conductors”--=table of conductors and
insulators=--mode of transmission--effect of heat--heating
effect of the current--=insulators=--impregnating compounds--
water as a conductor.
=RESISTANCE AND CONDUCTIVITY= =75 to 82=
=Standard of resistance=--conductivity of metals and
liquids--effect of heat--=laws of electrical resistance=--
conductivity--specific conductivity--=divided circuits=.
=ELECTRICAL AND MECHANICAL ENERGY= =83 to 92=
=Definitions:= energy, matter, molecule, work, foot-pound,
volt-coulomb, ampere-hour, power, horse power, =watt=, kilowatt,
watt-hour--mechanical equivalent of heat--=British thermal
unit=--=electrical horse power=--the farad.
=EFFECTS OF THE CURRENT= =93 to 104=
=Thermal effect=--use of heat from the current--magnetic
effect--chemical effect--=electrolysis=--electro-chemical
series--electric osmose--electric distillation--muscular
contractions--=electroplating=--electrotyping.
=MAGNETISM= =105 to 124=
Two kinds of magnetism--nature of each--=poles=--magnetic
field--magnetic force--=magnetic circuit=--magnetic flux--the
Maxwell--the Gauss--=magnetic effect of the current=--corkscrew
rule--solenoids--permeability--magnetic saturation--magnetomotive
force--=reluctance=--analogy between electric and magnetic
circuits--=hystereses=--residual magnetism.
=ELECTROMAGNETIC INDUCTION= =125 to 136=
=Faraday’s discovery=--Faraday’s machine--Faraday’s principle--
line of force--induction of current--laws of electromagnetic
induction--rules for direction of induced current--Fleming’s
rule--Ampere’s rule--the palm rule--=self-induction=.
=INDUCTION COILS= =137 to 154=
Self-induction--mutual induction--=primary induction coils=--
=secondary induction coils=--plain secondary induction
coils--secondary induction coils with vibrator and condenser;
=cycle of action=--magnetic vibrators--vibrator adjustment--
table of induction coil dimensions--table of sparking distances
in air--=points relating to induction coils=--wiring diagram.
=THE DYNAMO= =155 to 160=
Operation--=essential parts=--field magnets--armature--
=construction of dynamos=--parts; bed plate, field magnets,
armature, commutator, brushes.
=THE DYNAMO: BASIC PRINCIPLES= =161 to 170=
=Definitions=--essential parts--=elementary alternator=--
operation--direction of induced current--application of
Fleming’s rule--cycle of operation--=the sine curve=; its
construction and application.
=THE DYNAMO: CURRENT COMMUTATION= =171 to 180=
How the current is produced--=how direct current is obtained=--
the commutator--inductors--“continuous current”--action of four
coil elementary dynamo--=conditions for steadiness of the current=.
=CLASSES OF DYNAMO= =181 to 198=
Classification--bipolar and multi-polar dynamos--difference
between dynamo and magneto--self-exciting dynamo--=the series
dynamo=--regulation of series dynamo; difficulties experienced--
=the shunt dynamo=--adaptation--operation--characteristic--
regulation--=the compound dynamo=--service intended for--
regulation--over compounding--usual degree of over compounding--
short shunt--long shunt--voltage of short and long shunt machines
--separately excited dynamos--=Dobrowolski three wire dynamo.=
=FIELD MAGNETS= =199 to 220=
=Object=--essential parts--=classes of field magnet=--multi-polar
field magnets--construction--choice of materials--design--=pole
pieces=--eddy current--=laminated fields=--construction to reduce
reluctance of the magnetic circuit--magnetizing coils--=methods of
winding=--coil ends--insulation--attachment of coils--coil
connections--=heating=--ventilation.
INTRODUCTORY CHAPTER
The subject matter of this work relates to one of the secrets of creation
which appears to have been intended at the very beginning to be “sought
out.” This idea is expressed in a certain saying copied three or four
thousand years ago by the men of Hezekiah, King of Judah: from Solomon’s
proverbs: “_It is the glory of God to conceal a thing: But the glory of
Kings_ (i.e., _wise men_), _to search out a matter._”
In all that may be said hereafter through the work, it is admitted that
the results recorded are the determinations of experiments performed by an
incredible number of searchers extending through many ages. These
inquiries have been pursued with a generous rivalry which has permitted
discovery to be added to discovery, until the sum total has been wrought
into such exactness that it has been thoughtlessly stated that there is
nothing more, save its application.
It may be well, however, to state a few fundamental facts relating to
electricity: 1, Electricity and magnetism are one and the same thing; 2,
what is really known about it has come as a discovery and not as an
invention. Thus, we say the intrepid explorer discovered the pole, not
that he invented it. So with electricity it has been a subject of
discovery while its many applications to useful purposes have been
veritable inventions; 3, the earth itself is a magnet.
This last is shown by the fact that the earth affects a magnet just as one
magnet affects another. Magnets are bodies, either natural or artificial,
which have the property of attracting iron, and the power, when freely
suspended, of taking a direction toward the poles of the earth. The
natural magnet is sometimes called the _loadstone_. This word is said to
be derived from _loedan_, a Saxon word which signifies to guide. It is an
oxide of iron of a peculiar character, found occasionally in beds of iron
ore. Though commonly met with in irregular masses only a few inches in
diameter, however, loadstones of larger sizes are sometimes found.
By means of simple experiments it may be ascertained that the magnet has
the following general properties, viz: 1, power of attraction; 2, power of
repulsion; 3, power of communicating magnetism to iron or steel; 4,
polarity, or the power of taking a direction toward the poles of the
earth; 5, power of inclining itself toward a point below the horizon.
Speaking generally we may say, that magnetism is a department of
electrical science which treats of the properties and effects of the
magnet. The same terms are also used to denote the unknown cause of
magnetic phenomena, as when we speak of magnetism as excited, imparted,
and so on.
Lightning and the Northern Lights are displays of electricity on a grand
scale. Electricity is a term derived from the Greek word for _amber_, that
being the substance in which a property of the agent now denominated
electricity was first observed.
The ancient Greek philosophers were acquainted with the fact that amber,
when rubbed, acquired the property of attracting light bodies; hence the
effect was denominated electrical and in later times, the term electricity
has been used to denote the unknown cause of electrical phenomena, and
broadly the science which treats of electrical phenomena and their causes.
Electricity, whatever it may prove to be, is not _matter_ nor is it
_energy_; it is however a means or medium of transmitting energy.
If electricity is to transmit or convey energy along a wire,
this energy must be imparted to the electricity from some
external source, that is to say, before electricity can perform
any work it must be set in motion, against more or less
resistance. This involves that pressure must be applied, and to
obtain this pressure, energy must be expended from some external
source.
Accordingly, in electrical engineering, the first principle to be grasped
is that of _energy_. Without the expenditure of energy no useful work can
be accomplished.
Energy may be defined as _the capacity for performing work_.
Although electricity is not energy, electricity under pressure is a form
of energy spoken of as electrical energy.
In an expenditure of energy in this form, the electricity acts simply as a
transmission agent or medium to transmit the energy imparted to it in
causing it to flow.
In a similar manner, steam acts as a transmission agent or
medium to transmit the heat energy of the coal to the steam
engine, where it is converted into mechanical energy.
As just stated, electricity under pressure is a form of energy, and its
generation is simply a transformation of energy from one form into
another. Usually, mechanical energy is converted into electrical energy,
and a dynamo is employed for effecting the transformation.
In transforming the mechanical energy of waterfalls into
electric energy, this natural power of water due to its weight
and motion is first converted into rotary motion by a turbine or
water wheel, and then converted into electric energy by a
dynamo, or an alternator.
All dynamos are but machines for converting into electric energy
the energy which is given to them by some prime mover, as a
steam engine, a gas engine, by hydraulic or even by wind power.
All electric motors are merely machines for reconverting the
electric energy which they receive by means of the conducting
wires or mains, into mechanical energy.
All electric lamps are contrivances for converting into luminous
energy a percentage of the electric energy that is supplied
through the mains.
=Potential and Kinetic Energy.=--_Potential energy_ is the capacity for
performing work which a body possesses _by virtue of its position_.
_Kinetic energy_ is the capacity for performing work which a body
possesses _by virtue of its motion_.
It must be evident that position or motion given to a body
enables it to perform work. In the first instance, for example,
a heavy weight at the top of a high tower possesses potential
energy. A ten pound weight supported one foot above a plane has
ten foot pounds of potential energy.
The flywheel of a steam engine in motion is an example of a body
possessing kinetic energy. Some of this kinetic energy which was
stored up in the fly wheel during the working stroke is expended
in moving the engine over the “dead center,” and any other point
where no torque is produced by the pressure on the piston.
=Chemical Energy= can be converted into electric energy to a limited
extent by means of the electric battery, but the cost of this energy is so
high that it is commercially feasible only where small quantities are
required, and the cost of production is secondary to the convenience of
generation, as for signalling purposes, the operation of bells and
annunciators, etc.
The chemical energy of coal and other fuels cannot be directly
converted into electric energy. For power producing purposes,
the chemical energy of a fuel is first converted into heat by
combustion, and the heat thus obtained converted into mechanical
energy by some form of heat engine, and the mechanical energy
subsequently transformed into electric energy in an electric
generator.
_Energy cannot be created or destroyed._ This is the law known as the
=conservation of energy= which has been built up by Helmholtz, Thomson,
Joule and others. It teaches further, that energy can be transmitted from
one body to another or transformed in its manifestations.
Energy may be dissipated, that is, converted into a form from
which it cannot be recovered, as is the case with the great
percentage of heat escaping from the exhaust nozzle of a
locomotive or in the circulating water of a steamship, but the
total amount of energy in the universe, it is argued, remains
constant and invariable.
Following this law comes the doctrine of the =conservation of electricity=
as announced by Lippman, being undoubtedly the outcome of the ideas of
Maxwell and of Faraday as to the nature of electricity. According to their
doctrine, electricity _cannot be created or destroyed, although its
distribution may be altered_.
Lippman states that every charge of electricity has an opposite
and equal charge somewhere in the universe more or less
distributed; that is, the sum of positive charges is always
equal to the sum of negative charges.
In _altering the distribution of electricity_, we may cause =more= to
appear at one place and =less= at another, or may change it from the
condition of rest to that of motion, or may cause it to spin round in
whirlpools or vortices, which themselves can attract or repel other
vortices. According to this view all our electrical machines and batteries
are merely instruments for altering the _distribution_ of electricity by
moving some of it from one place to another, or for causing electricity,
when accumulated or heaped, together in one place, to do work in
returning to its former distribution.
Electrical engineering has developed largely and widely within a very
short time and its many applications has created so great a demand for
various kinds of electrical apparatus, that their manufacture forms one of
the leading industries.
Electricity is very valuable as a medium for the transmission of energy,
especially to long distances; it is also used to great advantage in
lighting, being free from the disagreeable properties of gas or oil.
Again, electricity finds various applications, in extracting gold from the
ore, pumping and ventilation of mines, traction, telephone, telegraph,
electroplating, therapeutics, etc.
These few, of its many applications will perhaps serve to indicate the far
reaching interest and importance of electricity, and possibly help to
kindle in the student something of the eagerness in his work and
enthusiasm without which he will fail to do justice either to his calling
or to himself.
SIGNS AND SYMBOLS
The following signs, symbols and abbreviations are almost universally
employed in descriptive and technical works on electrical subjects.
Although, in the arrangement of the Guides, the direct current and
alternating current matter has been kept separate, it is perhaps advisable
in the case of signs and symbols, to combine those relating to the
alternating current with the direct current and other symbols, making a
single table, rather than have them scattered throughout the work.
=1. Fundamental.=
_l_, Length. cm. = centimeter; in., or ″ = inch, ft. or
′ = foot.
M, Mass. gr. = mass of 1 gramme kg. = 1 kilogramme.
T, _t_, Time, _s_ = second.
=2. Derived Geometric.=
S, _s_, Surface.
E, Volume.
α, β, Angle.
=3. Derived Mechanical.=
_v_, Velocity.
ω, Angular velocity.
_r_, Momentum.
_a_, Acceleration.
_g_, Acceleration due to gravity = 32.2 feet per second.
F, _f_, Force.
W, Work.
P, Power.
δ, Dyne.
ε, Ergs,
ft. lb., Foot pound.
H.P., h.p. Horse power.
I.H.P., Indicated horse power.
B.H.P., Brake horse power.
E.H.P., Electrical horse power.
J, Joule’s equivalent.
_p_, Pressure.
K, Moment of inertia.
=4. Derived Electrostatic.=
_e_, Pressure difference.
_i_, Current.
_r_, Resistance.
_q_, Quantity.
_c_, Capacity.
_sc_, Specific inductive capacity.
=5. Derived Magnetic.=
_m_, Strength of pole.
[Script J], Intensity of magnetization.
[Script M], Magnetic moment.
[Script H], Horizontal intensity of earth’s magnetism.
[Script H], Field intensity.
φ, Magnetic flux.
[Script B], Magnetic flux density or magnetic induction.
[Script H], Magnetizing force.
[Script F], Magnetomotive force.
[Script R], Reluctance, magnetic resistance.
μ, Magnetic permeability.
κ, Magnetic susceptibility.
ν, Reluctivity (specific magnetic resistance).
=6. Derived Electromagnetic.=
R, Resistance, ohm.
O, do, megohm.
E, Volt, pressure.
E_im Impressed pressure.
E_a, E_o Active pressure; ohmic drop.
E_v Virtual pressure.
E_max Maximum pressure.
E_av Average pressure.
E_ef Effective pressure.
E_i Inductance pressure.
E_c Capacity pressure.
U, Difference of pressure, volt.
I, Intensity of current, ampere.
I_im Impressed current.
I_a Active current.
I_v Virtual current.
I_max Maximum current.
I_av Average current.
I_ef Effective current.
Q, Quantity of electricity, ampere-hour; coulomb.
C, Capacity, farad.
W, Electric energy, watt-hour; Joule.
P, Electric power, watt; kilowatt.
_p_, Resistivity (specific resistance) ohm centimeter.
G, Conductance, mho.
γ, Conductivity (specific conductivity).
Y, Admittance, mho.
Z, Impedance, ohm.
X, Reactance, ohm.
X_i Inductance reactance.
X_c Capacity reactance.
B, Susceptance, mho.
L, Inductance (coefficient of Induction), henry.
_v_, Ratio of electromagnetic to electrostatic unit of quantity
=3×10^{10} centimeters per second approximately.
=7. Symbols in general use.=
D, Diameter.
_r_, Radius.
_t_, Temperature.
θ, Deflection of galvanometer needle.
N, _n_, Number of anything.
π, Circumference ÷ diameter = 3.141592.
ω, 2π_f_ = 6.2831 × frequency, in alternating current.
~, _f_, Frequency, periodicity, cycles per second.
φ, Phase angle.
G, Galvanometer.
S, Shunt.
N, n, North pole of a magnet.
S, s, South pole of a magnet.
A.C. Alternating current.
D.C. Direct current.
P.D. Pressure difference.
P.F. Power factor.
C.G.S. Centimeter, Gramme, Second system.
B.&S. Brown & Sharpe wire gauge.
B.W.G. Birmingham wire gauge.
R.p.m. Revolutions per minute.
C.P. Candle power.
[--o--], Incandescent lamp.
[--X--], Arc lamp.
[Symbol: Condenser] OR [Symbol: Condenser] Condenser.
[Symbol: Battery of cells] Battery of cells.
[Symbol: Dynamo] Dynamo, or direct current motor.
[Symbol: Alternator] Alternator, or alternating current motor.
[Symbol: Converter] Converter.
[Symbol: Static transformer] Static transformer.
[Symbol: Inductive resistance] Inductive resistance.
[Symbol: Non-inductive resistance] Non-inductive resistance.
CHAPTER I
ELECTRICITY
=Nature and Source of Electricity.=--What is electricity? This is a
question that is frequently asked, but has not yet been satisfactorily
answered. It is a force, subject to control under well known laws.
While the nature and source of electricity still remain a mystery, many
things about it have become known, thus, it is positively assured that
electricity never manifests itself except when there is some mechanical
disturbance in ordinary matter.
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 be the true one, and if the
atmosphere of the earth be 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
_electromagnetic 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.
Electricity, it is also conceded, is without weight, and, while it is
without doubt, one and the same, it is for convenience sometimes
classified according to its motion, as:
1. Static electricity, or electricity _at rest_;
2. Current electricity, or electricity _in motion_;
3. Magnetism, or electricity _in rotation_;
4. Electricity _in vibration_ (radiation).
Other useful divisions are:
1. Positive;
2. Negative electricity;
3. Static;
4. Dynamic electricity.
=Static Electricity.=--This is a term employed to define electricity
produced by friction. It is properly employed in the sense of a static
charge which shows itself by the attraction or repulsion between charged
bodies.
When static electricity is discharged, it causes more or less of a
current, which shows itself by the passage of sparks or a brush discharge;
by a peculiar prickling sensation; by a peculiar smell due to its chemical
effects; by heating the air or other substances in its path; and sometimes
in other ways.[1]
=Current Electricity.=--This may be defined as the quantity of electricity
which passes through a conductor in a given time--or, electricity in the
act of being discharged, or electricity in motion.
An electric current manifests itself by heating the wire or conductor; by
causing a magnetic field around the conductor and by causing chemical
changes in a liquid through which it may pass.
=Dynamic Electricity.=--This term is used to define current electricity to
distinguish it from static electricity.
=Radiated Electricity.=--Electricity in vibration. Where the current
oscillates or vibrates back and forth with extreme rapidity, it takes the
form of waves which are similar to waves of light.
=Positive electricity.=--This term expresses the condition of the point of
an electrified body having the higher energy from which it flows to a
lower level. The sign which denotes this phase of electric excitement is
+; all electricity is either positive or negative.
=Negative Electricity.=--This is the reverse condition to the above and is
expressed by the sign or symbol -. These two terms are used in the same
sense as _hot_ and _cold_.
=Atmospheric Electricity= is the free electricity of the air which is
almost always present in the atmosphere. Its exact cause is unknown.
The phenomena of atmospheric electricity are of two kinds; there are the
well known manifestations of thunderstorms; and there are the phenomena of
continual slight electrification in the air, best observed when the
weather is fine; the Aurora constitutes a third branch of the subject.
[Illustration: FIG. 1.--The electric eel. There are several species
inhabiting the water, and which have the power of producing electric
discharges by certain portions of their organism. The best known of these
are the _Torpedo_, the _Gymnotus_, and the _Silurus_, found in the Nile
and the Tiger. The Electric Ray, of which there are three species
inhabiting the Mediterranean and Atlantic is provided with an electric
organ on the back of its head, as shown in the illustration. This organ
consists of laminæ composed of polygonal cells to the number of 800 or
1000, or more, supplied with four large bundles of nerve fibres; the under
surface of the fish is -, the upper +. In the Surinam eel, the electric
organ goes the whole length of the body along both sides. It is able to
give a very severe shock, and is a formidable antagonist when it has
attained its full length of 5 or 6 feet.]
=Frictional Electricity= is that produced by the friction of one substance
against another.
=Resinous Electricity.=--The kind of electricity produced upon a resinous
substances such as sealing wax, resin, shellac, rubber or amber when
rubbed with wool or fur. Resinous electricity is _negative electricity_.
=Vitreous Electricity.=--A term applied to the positive electricity
developed in a glass rod by rubbing it with silk. This electric charge
will attract to itself bits of pith or paper which have been repelled from
a rod of sealing wax or other resinous substance which had been rubbed
with wool or fur.