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 en-ergy 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. 4 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. '', '', Angle. 3. Derived Mechanical. v, Velocity. '', Angular velocity. r, Momentum. a, Acceleration. g, Acceleration due to gravity = 32.2 feet per second. F, f, Force. W, Work. P, Power. '', Dyne. '', Ergs, 5 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. , Intensity of magnetization. , Magnetic moment. , Horizontal intensity of earth's magnetism. , Field intensity. '', Magnetic flux. , Magnetic flux density or magnetic induction. , Magnetizing force. , Magnetomotive force. , Reluctance, magnetic resistance. m, Magnetic permeability. '', Magnetic susceptibility. '', Reluctivity (specific magnetic resistance). 6. Derived Electromagnetic. R, Resistance, ohm. O, do, megohm. E, Volt, pressure. Eim Impressed pressure. Ea, Eo Active pressure; ohmic drop. Ev Virtual pressure. Emax Maximum pressure. Eav Average pressure. Eef Effective pressure. Ei Inductance pressure. Ec Capacity pressure. U, Difference of pressure, volt. I, Intensity of current, ampere. Iim Impressed current. Ia Active current. Iv Virtual current. Imax Maximum current. Iav Average current. Ief Effective current. Q, Quantity of electricity, ampere-hour; coulomb. C, Capacity, farad. W, Electric energy, watt-hour; Joule. 6 P, Electric power, watt; kilowatt. p, Resistivity (specific resistance) ohm centimeter. G, Conductance, mho. '', Conductivity (specific conductivity). Y, Admittance, mho. Z, Impedance, ohm. X, Reactance, ohm. Xi Inductance reactance. Xc Capacity reactance. B, Susceptance, mho. L, Inductance (coefficient of Induction), henry. v, Ratio of electromagnetic to electrostatic unit of quantity = 3x1010 centimeters per second approximately. 7. Symbols in general use. D, Diameter. r, Radius. t, Temperature. '', Deflection of galvanometer needle. N, n, Number of anything.
p, Circumference / diameter = 3.141592.
'', 2pf = 6.2831 x frequency, in alternating current.
~, f, Frequency, periodicity, cycles per second.
'', 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.
, Incandescent lamp.
, Arc lamp.
, OR , Condenser.
, Battery of cells.
, Dynamo, or direct current motor.
, Alternator, or alternating current motor.
, Converter.
, Static transformer.
, Inductive resistance.
, Non-inductive resistance.
1
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
