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abscissae alternate-current machines alternating current amperes applied armature battery brushes capacity carbons cent Chance Brothers characteristic curve coils column commutator condenser conductors connected constant convolutions copper core cost current passing deflection determined diameter difference of potential diminish direction distance dynamo machine effect efficiency electric arc electric light electrical resistance electro-magnet electromotive force electrostatic energy Engineers equation experiments fact flashes galvanic galvanometer give given Gramme machine heat hysteresis increase induction iron John Hopkinson lamp lighthouse line integral magnetic circuit magnetic field magnetising force manganese mathematical maximum means measured mechanical motor non-magnetic observed obtained open circuit ordinates paper plates pole pole-pieces position potential difference practical primary properties pulley quantity represents residual charge resistance revolutions per minute ring secondary circuit self-induction shaft Siemens speed steel supply Suppose temperature theory tion transformer varying volts watts wire zinc

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Page 66 - They show us that although by doubling the velocity of the machine we really double the electromotive force at any time, we do not double the current passing, nor the work done by the machine ; but we may see that if we double the velocity of the machine, we may work through double the external resistance, and still obtain the same current. In what precedes, it has been assumed that the copper wires are the only conducting bodies moving in the magnetic field. In many cases the moving wire-coils of...

Page 269 - A society for the general advancement of Mechanical Science, and more particularly for promoting the acquisition of that species of knowledge which constitutes the profession of a Civil Engineer...

Page 286 - Admission to its sanctuary, and to the privileges and feelings of a votary, is only to be gained by one means, — sound and sufficient knowledge of mathematics, the great instrument of all exact inquiry, without which no man can ever make such advances in this or any other of the higher departments of science as can entitle him to form an independent opinion on any subject of discussion within their range.

Page 126 - The currents in the fixed coils around the magnets are not the only magnetising forces applied in a dynamo machine ; the currents in the moving coils of the armature have also their effect on the resultant field. There are in general two independent variables in a dynamo machine, the current around the magnets and the current in the armature, and the relation of EMF to currents is fully represented by a surface. In well-constructed machines the effect of the latter is reduced to a minimum, but it...

Page 74 - ... determining the maximum work which can be transmitted when the electromotive force of the generating machine depends on the current passing through the armature, as, indeed, it nearly always does, referring to Fig. 10. OPB is the characteristic curve of the generating machine ; construct a derived curve Y A thus, at successive points...

Page 269 - June 19, 1905. acquisition of that species of knowledge which constitutes the profession of a civil engineer, being the art of directing the great sources of power in nature for the use and convenience of man, as the means of production and of traffic in states both for external and internal trade, as applied in the construction of roads, bridges, aqueducts, canals, river navigation, and docks, for internal intercourse and exchange, and in the construction of ports...

Page 215 - ... the one hand, and ordinary substances on the other. On this diagram I have taken the galvanometer deflections to the same scale for iron, and for such substances as glass or wood. You see that the deflections in the case of glass or wood, to the same scale, are so small as to be absolutely inappreciable, whilst the deflection for iron at one point of the curve is something like 2000 times as great as for non-magnetic substances. This extraordinary property is possessed by only two other substances...

Page 256 - ... to take them back in the evening, and for the rest of the day it must be content to be comparatively idle. In this case the services cannot be stored. The line must be of a carrying capacity equal to the greatest demand, and if this be great for a very short time the total return for the day must be small in comparison with the expense of rendering the service. In such a case it would not be inappropriate to charge more for carrying a person in the busy time than in the slack time, for it really...

Page 83 - ... candles per cubic foot of gas, a result you would be puzzled to obtain in 16-candle gas burners. With arc lights instead of incandescent lamps many times as much light could be obtained. At the present time, lighting by electricity in London must cost something more than lighting by gas. Let us see what are the prospects of reduction of this cost? Beginning with the engine and boiler, the electrician has no right to look forward to any marked and exceptional advance in their economy. Next comes...

Page 55 - OA of abscissae, so that the ratio -~-^ may represent the necessary metallic resistance of the circuit. Through the point B, thus obtained, draw a tangent to the curve, touching it at C, and cutting OA in D. Then the speed of the machine, corresponding to the particular curve employed, must be diminished in the ratio ^—r , in order that an exceedingly small arc may be just possible.