Elementary Lessons in Electricity & Magnetism |
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Page vii
... of alternate currents , of which in 1881 little was known , have been forced into study by the extension of their industrial uses in telephony and in electric lighting . 287994 Entirely new is the use of polyphase alternate currents and ...
... of alternate currents , of which in 1881 little was known , have been forced into study by the extension of their industrial uses in telephony and in electric lighting . 287994 Entirely new is the use of polyphase alternate currents and ...
Page 1
... known to us only by the effects which it produces and by various manifestations called electrical . These manifestations , at first obscure and even mysterious , are now well understood ; though little is yet known of the precise nature ...
... known to us only by the effects which it produces and by various manifestations called electrical . These manifestations , at first obscure and even mysterious , are now well understood ; though little is yet known of the precise nature ...
Page 8
... known that these effects which appear like a repul- sion and an attraction between bodies at a distance from one another are really due to actions going on in the medium between them . The positive charge does not really attract the ...
... known that these effects which appear like a repul- sion and an attraction between bodies at a distance from one another are really due to actions going on in the medium between them . The positive charge does not really attract the ...
Page 10
... known fluid in almost every other respect . It possesses no weight ; it repels itself . It is , moreover , quite impossible to conceive of two fluids whose properties should in every respect be the precise opposites of one another . For ...
... known fluid in almost every other respect . It possesses no weight ; it repels itself . It is , moreover , quite impossible to conceive of two fluids whose properties should in every respect be the precise opposites of one another . For ...
Page 18
... when the charge thus imparted to them is greater . For exact measurement , however , of the degree of electrification , recourse must be had to the instruments known as Electrometers 18 PART I ELECTRICITY AND MAGNETISM.
... when the charge thus imparted to them is greater . For exact measurement , however , of the degree of electrification , recourse must be had to the instruments known as Electrometers 18 PART I ELECTRICITY AND MAGNETISM.
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Common terms and phrases
acid action alternate currents amperes angle anode armature attracted ball battery capacity carbon cell centimetres chemical circuit coil condenser conductor copper current flows curve deflexion diamagnetic dielectric difference of potential direction discharge disk distance dynamo dynes earth electric force electrified electrified body electrolytic electromagnet electrometer electromotive-force electroscope electrostatic energy equal galvanometer glass gramme heat Hence hydrogen induction influence machine instrument insulated internal resistance inversely kathode knob lamp length LESSON Leyden jar light lines of force liquid machine magnetic field magnetic force magnetic lines magnetic pole measure metal method motor move N-seeking needle negative Ohm's law ohms opposite oscillations pass piece placed plate platinum polarization positive produced proportional quantity of electricity repelled rotation round rubbed self-induction shown in Fig spark sphere steel strength substances sulphate surface temperature tend thin tion tricity tube turns voltage volts zinc
Popular passages
Page 585 - As a unit of current, the international ampere, which is onetenth of the unit of current of the CGS system of electromagnetic units, and which is represented sufficiently well for practical use by the unvarying current which, when passed through a solution of nitrate of silver in water, and in accordance with accompanying specifications deposits silver at the rate of 0-001118 of a gram per second.
Page 584 - As a unit of resistance, the international ohm, which is based upon the ohm equal to 10" units of resistance of the CGS system of electromagnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice, 14.4521 grams in mass, of a constant cross-sectional area and of the length of 106.3 centimetres.
Page 585 - The liquid should consist of a neutral solution of pure silver nitrate, containing about 15 parts by weight of the nitrate to 85 parts of water. The resistance of the voltameter changes somewhat as the current passes. To prevent these changes having too great an effect on the current, some resistance besides that of the voltameter should be inserted in the circuit.
Page 585 - ... the electro-motive force that, steadily applied to a conductor whose resistance is one international ohm, will produce a current of one international ampere, and which is represented sufficiently well for practical use by { £ %$ of the electro-motive force between the poles or electrodes of the voltaic cell known as Clark's cell, at a temperature of 15°...
Page 586 - As a unit of work, the joule, which is equal to 107 units of work in the CGS system, and which is represented sufficiently well for practical use by the energy expended in one second by an international ampere in an international ohm. As a unit of power, the watt, which is equal to 10...
Page 318 - I say, if these things are so, may not the knowledge of this power of points be of use to mankind, in preserving houses, churches, ships, &c. from the stroke of lightning, by directing us to fix on the highest parts of those edifices, upright rods of iron made sharp as a needle, and gilt to prevent rusting, and from the foot of those rods a wire down the outside of the building into the ground, or down round one of the shrouds of a ship...
Page 588 - Then insert the cork and zinc rod, passing the glass tube through the hole prepared for it. Push the cork gently down until its lower surface is nearly in contact with the liquid. The air will thus be nearly...
Page 589 - ... tube through the hole prepared for it. Push the cork gently down until its lower surface is nearly in contact with the liquid. The air will thus be nearly all expelled, and the cell should be left in this condition for at least twenty-four hours before sealing, which should be done as follows.
Page 585 - As a unit of electromotive force, the international volt, which is the electromotive force that, steadily applied to a conductor whose resistance is one international ohm, will produce a current of one international ampere, and which is represented sufficiently well for practical use by ^2.
Page 318 - Would not these pointed rods probably draw the electrical fire silently out of a cloud before it came nigh enough to strike, and thereby secure us from that most sudden and terrible mischief?