Modern Practice of the Electric Telegraph: A Handbook for Electricians and OperatorsRussell brothers, 1869 - 128 стор. |
Загальні терміни та фрази
action adjusted annealed apparatus arrangement attached binding screws bracket broken button repeater cable carbon cause cell Chatterton's compound conductor copper copper wire cuit dashes defective insulation diameter direction distance distant end earth ELECTRIC TELEGRAPH electricity electro-magnet electro-motive force employed equal escape extra local magnets fault galvanized galvanometer glass governor magnet ground connection ground wire Grove battery gutta-percha Gutta-Percha Company inches increased instrument iron wire joint resistance latter leakage length lightning arrester line wire local battery loop main battery main line manufactured measure ment metallic miles Morse needle nitric acid Ohm's law ohms operator opposite paraffine passes placed plate pole porous cup portion position practice principle resistance coils rheostat rous Cups send dots shown in fig signals sounder space station statute mile sulphuric acid switch telegraph lines terminal station tery testing thence tion usually versine weather western main circuit wire leading zinc
Популярні уривки
Сторінка 103 - To become an expert sending and receiving operator requires a vast amount of time and patience, and the most unwearied application. Remember that whatever is worth doing at all, is worth doing well.
Сторінка 91 - The fundamental demands of health require the purification of a classroom by direct sunlight; but it is also necessary to introduce this all-important purifying agent in such a manner as to prevent as far as possible the direct rays of the sun from falling on the desks and books of the pupils while they are engaged in study. If the windows of a classroom are placed on the north side of a building located in any section of our country, very little direct sunshine will ever enter, and during the school...
Сторінка 64 - ... or in other words the force of the current is equal to the sum of the electro-motive forces divided by the sum of the resistances.
Сторінка 124 - This law only holds good for bars of iron whose length is considerably greater than their diameter, for feeble currents of electricity ; and under the supposition that the number of convolutions of wire is not so great as materially to diminish the influence exerted by the outer coils upon the bar of iron.
Сторінка 121 - Let it be required to know the resistance at 0° of a conductor of pure hard copper, weighing 400 Ibs. per knot. This is equivalent to 460 grains per foot. The resistance of a wire weighing one grain per foot is 0-2106 ; therefore...
Сторінка 122 - If the diameter of the wire be given instead of its weight per knot, the calculation is still simpler, and the constant for English measures would be taken from the third column of the Table. Thus the resistance at 0° of a knot of pure hard-drawn copper wire 0-1 inch diameter would be —— =6-05.
Сторінка 44 - ... sound, reflected and reverberated among the clouds, produces the long-continued and solemn roll, which forms one of the sublimest characteristics of a thunder-storm. It is often imagined that lightning always moves towards the earth. But there is reason to suppose that discharges are sometimes made from the earth to the clouds, as well as from the clouds to the earth. — It is not difficult to measure the distance of thunder-clouds from the earth. Sound moves at the rate of .eleven hundred and...
Сторінка 127 - Ibs.* The strain varies directly as the weight of the wire, and inversely as the dip or versine ; it increases as the square of the span if the dip be constant, but to preserve a given strain the dip or versine must increase as the square of the span, or L* :/«:: V :v.
Сторінка 125 - Q decreases as n decreases, supposing the electric force to remain constant. Hence it is evident that a certain proportion between the resistance of the wire and that of the remaining portions of the circuit must be preserved, to obtain the maximum magnetic force. This relation is found to be the following: — ' When the resistance of the coils of the electro-magnet is equal to the resistance of the rest of the circuit, ie the conducting wire and battery, the magnetic force is a maximum.
Сторінка 124 - R ; then take the deflection of E' and call it R', adding resistance to make the deflection the same. Then ExP. 103. Measure EMF by comparison. Call the EMF of two batteries E and E' ; join them up successively in circuit with the same galvanometer, and, by varying the resistance, cause them both to give the same deflection ; their forces will then be in direct proportion to the total resistances in circuit in each case ; or, E'=Ex?j-, R when R (including that of battery, galvanometer, and the adjustable...