Online Encyclopedia

ELECTRICITY

Online Encyclopedia
Originally appearing in Volume V09, Page 180 of the 1911 Encyclopedia Britannica.
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ELECTRICITY. This article is devoted to a general sketch of the history of the development of electrical knowledge on both the theoretical and the practical sides. The two great branches of electrical theory which concern the phenomena of electricity at rest, or " frictional " or " static " electricity, and of electricity in motion, or electric currents, are treated in two separate articles, ELECTROSTATICS and ELECTROKINETICS. The phenomena attendant on the passage of electricity through solids, through liquids and through gases, are described in the article CONDUCTION, ELECTRIC, and also ELECTROLYSIS, and the propa, gation of electrical vibrations in ELECTRIC WAVES. The inter-connexion of magnetism (which has an article to itself) and electricity is discussed in ELECTROMAGNETISM, and these manifestations in nature in ATMOSPHERIC ELECTRICITY; AURORA POLARIS and MAGNETISM, TERRESTRIAL. The general principles of electrical engineering will be found in ELECTRICITY SUPPLY, and further details respecting the generation and use of electrical power are given in such articles as DYNAMO; MOTORS, ELECTRIC; TRANSFORMERS; ACCUMULATOR; POWER TRANSMISSION: Electric; TRACTION; LIGHTING: Electric; ELECTROCHEMISTRY and ELECTROMETALLURGY. The principles of telegraphy (land, submarine and wireless) and of telephony are discussed in the articles TELEGRAPH and TELEPHONE, and various electrical instruments are treated in separate articles such as AMPERE-METER; ELECTROMETER; GALVANOMETER; VOLTMETER; WHEATSTONE'S BRIDGE; POTENTIOMETER; METER, ELECTRIC; ELECTROPHORUS; LEYDEN JAR; &C. The term " electricity " is applied to denote the physical agency which exhibits itself by effects of attraction and repulsion when particular substances are rubbed or heated, also in certain chemical and physiological actions and in connexion with moving magnets and metallic circuits. The name is derived from the word electrica, first used by William Gilbert (1544–1603) in his epoch-making treatise De magnete, magneticisque corporibus, et de magna magnete tellure, published in 1600,1 to denote substances which possess a similar property to amber (= electrum, from i XeKrpov) of attracting light objects when rubbed. Hence the phenomena came to be collectively called electrical, a term first used by William Barlowe, archdeacon of Salisbury, in 1618, and the study of them, electrical science. Historical Sketch. Gilbert was the first to conduct systematic scientific experiments on electrical phenomena. Prior to his date the scanty knowledge possessed by the ancients and enjoyed in the middle ages began and ended with facts said to have been familiar to Thales of Miletus (600 B.C.) and mentioned by Theophrastus (321 B.C.) and Pliny (A.D. 70), namely, that amber, jet and one or two other substances possessed the power, when rubbed, of attracting fragments of straw, leaves or feathers. Starting with careful and accurate observations on facts concerning the mysterious properties of amber and the lodestone, Gilbert laid the foundations of modern electric and magnetic science on the true experimental and inductive basis. The subsequent history of electricity may be divided into four well-marked periods. The first extends from the date of publication of Gilbert's great treatise in 1600 to the invention by Volta of the voltaic pile and the first production of the electric current in 1799. The second dates from Volta's discovery to the discovery by Faraday in 1831 of the induction of electric currents and the creation of currents by the motion of conductors in magnetic fields, which initiated the era of modern electrotechnics. The third covers the period between 1831 and Clerk Maxwell's enunciation of the electromagnetic theory of light in 1865 and the invention of the self-exciting dynamo, which marks another great epoch in the development of the subject; and the fourth comprises the modern development of electric theory and of absolute quantitative measurements, and above all, of the applications of this knowledge in electrical engineering. We shall sketch briefly the historical progress during these various stages, and also the growth of electrical theories of electricity during that time.
End of Article: ELECTRICITY
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