Elementary Lessons in Electricity & MagnetismMacmillan and Company, 1881 - 446 páginas |
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Términos y frases comunes
acid action angle armature attracted ball battery bismuth brass carbon centimetres charge of electricity chemical circuit coil condenser conductor copper current flows Daniell's cells deflection diamagnetic dielectric difference of potential direction disc discharge distance dynes earth earth's magnetism electric force electrified body electrolytic electromagnet electrometer electromotive-force electroscope electrostatic equal Faraday galvanometer grammes heat Hence hydrogen instrument insulated internal resistance inversely iron knob Leclanché cells length Lesson Leyden jar light lines of force lines-of-force liquid magnetic force magnetic pole magnetic potential magnetic shell magnetised measured metal move N.-seeking pole negative Ohm's law ohms opposite kinds pass piece placed plate platinum polarisation positive produced proportional quantity of electricity repelled repulsion rotation round rubbed shown in Fig spark sphere steel strength substances sulphuric surface tangent tangent galvanometer thin torsion balance tricity tube unit of electricity velocity voltaic volts weber wire zinc
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Página 257 - 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...
Página 268 - The unit difference of magnetic potential exists between two points, when it requires the expenditure of one erg of work to bring a unit magnetic pole from one point to the other against the magnetic forces.
Página 257 - 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?
Página 268 - ... currents in the neighbourhood, without the presence of a magnet. Since the peculiarity of the magnetic field consists in the presence of a certain force, we may numerically express the properties of the field by measuring the strength and direction of the force, or, as it may be worded, the intensity of the field and the direction of the lines of force.
Página 208 - The unit of surface is the square centimetre. Volume. — The unit of volume is the cubic centimetre. Velocity. — The unit of velocity is the velocity of a body which moves through unit distance in unit time, or one centimetre per second.
Página 209 - The unit of force is that force which, acting for one second on a mass of one gramme, gives to it a velocity of one centimetre per second.
Página 279 - ... unit difference of potential exists between two points when it requires the expenditure of one erg of work to bring a unit of -)- electricity from one point to the other against the electric force.
Página x - ... can neither create nor destroy electricity, though we may alter its distribution, may make more to appear at one place and less at another, may change it from the condition of rest to that of motion, or may cause it to spin round in whirlpools or vortices which themselves can attract or repel other vortices. According to this view all our electrical machines and batteries are merely instruments for altering the distribution of electricity by moving some of it from one place to another, or for...
Página 158 - Every portion of the circuit is acted upon by a force urging it in such a direction as to make it enclose within its embrace the greatest possible number of lines offeree.
Página 254 - Giving light ; color of the light ; crooked direction ; swift motion ; being conducted by metals ; noise in exploding ; conductivity in water and ice ; rending imperfect conductors; destroying animals; melting metals; firing inflammable substances ; sulphureous smell (ozone) ; and similarity of appearance between the brush discharge from the tips of masts and spars sometimes seen at sea, called St. Elmo's fire by the sailors, and the slow escape from points on an electrical machine or a leyden jar.