ELECTRICITY AND ELECTRICAL MACHINERY.
Each kind of power requires its own special machinery so constructed and adapted as to utilize it; hence, to be serviceable to mankind, electricity demands machinery suited to its nature; what that is, will be indicated in the following few paragraphs.
Electricity is a name derived from the Greek wordelectron—amber. It was discovered more than 2,000 years ago that amber when rubbed with a Fox’s tail possessed the curious property of attracting light bodies. It was discovered afterwards that this property could be produced in a dry steam jet by friction, and in A. D. 1600 or thereabouts, that glass, sealing-wax, etc., were also affected by rubbing, producing electricity.
Whatever electricity is, it is impossible to say, but for the present it is convenient to consider it as a kind of invisible something which pervades all bodies. While the nature and source of electricity are a mystery, and a constant challenge to the inquirer, 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, and every exhibition of electricity in any of its multitudinous ways may always be traced back to a mass of matter.
Note.—The great forces of the world are invisible and impalpable; we cannot grasp or handle them; and though they are real enough, they have the appearance of being very unreal. Electricity and gravity are as subtle as they are mighty; they elude the eye and hand of the most skillful philosopher. In view of this, it is well for the average man not to try to fathom, too deeply, the science of either. To take the machines and appliances as they are “on the market,†and to acquire the skill to operate them, is the longest step toward the reason for doing it, and why the desired results follow.
Note.—The great forces of the world are invisible and impalpable; we cannot grasp or handle them; and though they are real enough, they have the appearance of being very unreal. Electricity and gravity are as subtle as they are mighty; they elude the eye and hand of the most skillful philosopher. In view of this, it is well for the average man not to try to fathom, too deeply, the science of either. To take the machines and appliances as they are “on the market,†and to acquire the skill to operate them, is the longest step toward the reason for doing it, and why the desired results follow.
Electricity, it is also conceded, is without weight, and, while electricity is, without doubt, one and the same, it is for convenience sometimes classified according to its motion, as—
1.Static electricity, or electricityat rest.2.Current electricity, or electricityin motion.3.Magnetism, or electricityin rotation.4.Electricity in vibration.
Other useful divisions are into—
1.Frictionaland2.Dynamical,
And into—
1.Static, as the opposite of2.Dynamic electricity.
There are still other definitions or divisions which are in every-day use, such as “vitreous†electricity, “atmospheric†electricity, “resinous†electricity, etc.
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 an unusual smell due to its chemical effects; by heating the air or other substances in its path; and sometimes in other ways.
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 conductorand by causing chemical changes in a liquid through which it may pass.
Note.—Staticsis that branch of mechanics which treats of the forces which keep bodies at rest or in equilibrium.Dynamicstreats of bodies in motion. Hence static electricity is electricity at rest. The earth’s great store of electricity is at rest or in equilibrium.
Note.—Staticsis that branch of mechanics which treats of the forces which keep bodies at rest or in equilibrium.Dynamicstreats of bodies in motion. Hence static electricity is electricity at rest. The earth’s great store of electricity is at rest or in equilibrium.
Radiated electricityis 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 ashotandcold.
Atmospheric electricityis 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.
Dynamic Electricity.—This term is used to define current electricity to distinguish it from static electricity. This is the electricity produced by the dynamo.
Frictional electricityis that produced by the friction of one substance against another.
Resinous Electricity.—This is a term formerly used, in place of negative electricity. The phrase originated in the well known fact that a certain (negative) kind of electricity was produced by rubbing rosin.
Vitreous electricityis a term, formerly used, to describe that kind of electricity (positive) produced by rubbing glass.
Magneto-electricityis electricity in the form of currents flowing along wires; it is electricity derived from the motion of magnets—hence the name.
Voltaic Electricity.—This is electricity produced by the action of the voltaic cell or battery.
Electricity itself is the same thing, or phase of energy, by whatever source it is produced, and the foregoing definitions are given only as a matter of convenience.