N. Hawkins

“ To sustain a current of electricity requires energy. To sustain magnetism requires no energy. A current of electricity is always accompanied by a magnetic field of peculiar form. Magnetism alone cannot produce electricity. Electricity can do work; but magnetism cannot in the same sense—and alike with electricity, neither can it exist without contact with matter. ”

“ The production of electricity is simply a transformation of energy from one form into another, usually mechanical energy is changed into electrical energy and a dynamo is simply a device for effecting the transformation. ”

“ Bodies in which the electric current moves freely are called conductors, and those in which it does not move freely are called insulators. There is, however, no substance so good a conductor as to be devoid of resistance, and no substance of such high resistance as to be a non-conductor. ”

“ It should always be remembered that electricity is something real, although not easily defined. And then, too, while it is not matter and not energy, yet under proper conditions (it having the power of doing work) it is convenient to speak of its performances as electric energy. ”

“ It is evident that a perfect system of electrical measurement should take account of the total amount of energy consumed, and should depend not only upon the volume of current, but also upon the pressure at which the current is applied. ”

“ He calls particular attention to the important fact that the “resistance of one kind or another is always the agent that acts to alter energy from one form to another,” and suggests that electricity is simply a form or manifestation that energy may assume under given conditions, and generally is a mere transitory stage between the mechanical form and the heat form. ”

“ Fig. 24.—Lines of force of a charged sphere and a conductor under induction. The negative electrification on the end a of the cylinder indicates that a certain number of lines end there, while the positive electrification on the end b similarly indicates that an equal number of lines set out from that end. It is one of the fundamental properties of a conductor that it yields instantly to the smallest electric force, and that no electric force can be permanently maintained within the substance of a conductor in which no current is passing. ”

“ 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. ”

“ 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. ”

“ Electricity, though not a substance, can be associated with matter, and its transmission requires energy. While it is neither a gas nor a liquid, its behavior sometimes is similar to that of a fluid so that it is said to “flow” through a conductor. This expression of flowing does not really mean that there is an actual movement in the wire, similar to the flow of water in a pipe, but is a convenient expression for the phenomena involved.
Effect of Heat.—The conducting power of bodies is affected in different ways by their temperature. In the metals it is diminished by elevation of temperature ”

“ 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. ”

“ Action of a Primary Cell.—The fundamental fact on which the electro-chemical generation of current depends is, that if a plate of metal be placed in a liquid there is a difference of electrical condition produced between them of such sort that the metal either takes a lower or higher electrical potential than the liquid, according to the nature of the metal and the liquid. ”

“ When the elements are connected at their terminals by a wire or conductor a chemical action takes place, producing a current which flows from the copper to the zinc. This device is called a cell, and the combination of two or more of them connected so as to form a unit is known as a battery. The word battery is frequently used incorrectly for a single cell. That terminal of the element from which the current flows is called the plus or positive pole, and the terminal of the other element the negative pole. ”

“ When the charge of electricity is removed from a charged body it is said to be discharged. Good conductors of electricity are instantaneously discharged if touched by the hand or by any conductor in contact with the ground, the charge thus finding a means of escaping to earth. A body that is not a good conductor may be readily discharged by passing it rapidly through the flame of a lamp or candle; for the flame instantly carries off the electricity and dissipates it in the air. ”

“ 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. ”

“ 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. ”

“ When a conducting circuit is moved in a magnetic field, so as to alter the number of lines of force passing through it, or when the strength of the field is varied so as to either increase or decrease the number of lines of force passing through the circuit, a current is induced therein which lasts only during the interval of change in the number of lines of force embraced by the circuit. ”

“ The unit of electromotive force, called the volt, is the electric pressure produced by cutting 100,000,000 lines per second, usually expressed 108.
Fig. 130.—Experiment illustrating Lenz’s law which states that in all cases of electromagnetic induction, the direction of the induced current is such as to tend to stop the motion producing it. In the experiment, in order to produce the induced current, energy must be expended in bringing the magnet to the coil and in taking it away, which is in accordance with the law of conservation of energy. ”

“ Work is the overcoming of resistance through a certain distance.
As a quantity of water moving from a higher to a lower level will do work, so also will a quantity of electricity falling through a difference of potential. ”

“ The power of resisting breakdown is a complex quality, for it is not solely dependent on mere puncturing pressure, but also on mechanical goodness, and to a certain extent on the insulation resistance. ”

“ Carbon possesses a natural power to prevent a limited amount of polarization by absorbing the hydrogen gas coming from the zinc rod; hence it is used in various shapes for open circuit cells, which gives rise to as many different names, such as Samson, Hercules, Law, National, Standard, etc. In all these types of cell, sal-ammoniac and zinc are used, and by corrugating the carbon, fluting it, or making concentric cylinders, special merits are obtained in each case. ”

“ The induction coil has always been a popular piece of apparatus with those interested in electrical science; the experiments which can be performed with its aid are very numerous. It is of considerable importance, especially in its application to such useful purposes as X ray work, wireless telegraphy and ignition for gas engines. The latter has caused manufacturers to give much attention to the development of the induction coil, resulting in many refinements of design and construction. ”

“ If the plates be connected by a wire outside the electrolyte, the tendency which dissimilar electrical charges have to neutralize one another causes a flow of negative electricity through the wire from zinc to copper, and a positive flow in the opposite direction. ”

“ 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. ”

“ The electromotive force generated in the dynamo causes the current of electricity to pass from a lower to a higher potential in the machine, and from the higher back to the lower potential in the external circuit; that is, the dynamo generates electrical pressure which overcomes the resistance or opposition to the current flow in the circuit. The pump produces a mechanical pressure which, for instance, may be used to force water into an elevated reservoir against the back pressure due to its weight.156
Fig. ”

“ For cores, wrought iron is most desirable, as requiring the smallest amount of material for a given flux. There is a saving in copper due to using wrought iron for the core since, on account of its small size, the length of each turn of the204 magnetizing coil is reduced. For heavy yokes, where lightness is not essential, but very often the reverse, cast iron is used, as its cross section can be made larger than that of the cores, this increase in area serving to give strength and rigidity to the machine. ”

“ When the sulphuric acid in a cell acts in the zinc element and produces sulphate of zinc, a certain amount of work is done which is manifested partly in the form of useful electric energy, and partly as heat which warms the electrolyte and which is thereby lost for all practical purposes. ”

“ Ans. A dynamo is a machine for filling and emptying conducting loops with magnetic flux, and utilizing the electromotive force thus induced in them for the production of current in the external circuit. ”

“ 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. ”

“ In all well designed shunt dynamos, the resistance of the shunt circuit is always very great, as compared with the resistance of the armature and external circuit, the strength of the current flowing in the shunt coils being very small even in the largest machines. ”

“ It is highly important that the copper oxide plates be completely submerged in the solution of caustic potash, and that heavy paraffin oil be poured on top of the solution to the depth of about 1⁄4 of an inch to exclude the air. If oil be not used, the formation of creeping salts will reduce the life of the battery fully two-thirds. The battery has a low electromotive force, about 0.7 of a volt, but as the internal resistance is also very low, quite a large current can be drawn from the cell. ”

“ Conductivity of Metals and Liquids.—The metals in general, conduct well, hence their resistance is small, but metal wires must not be too thin or too long, or they will resist too much, and permit only a feeble current to pass through them. The liquids in the battery do not conduct nearly so well as the metals, and different liquids have different resistances. Pure water will hardly conduct at all, unless the voltage be very high. ”

“ The charge of electricity, which only elevates the temperature of one conductor a small amount, will sometimes render another incandescent, and will vaporize a third.
Insulators.—The term insulator is used in two ways: 1, as in insulating substance or medium, and 2, as a specially formed piece of some insulating material, such as glass, porcelain, etc. No substance has the power of absolutely preventing the passage of electric currents between conductors but many have sufficient insulating power for practical purposes. ”