Electricity Meters A Treatise on the General Principles, Construction, and Testing of Continuous Current and Alternating Current Meters for the Use of Electrical Engineers and Students

1.It may be taken as an axiom of electrical ignition that the closer its conditions resemble those in the explosion wave front the more readily will it occur. These conditions are high temperature and pressure, and in the case of hydrocarbons combustion to carbon monoxide. They are also characteristic of condenser discharge sparks, for in the first place the surface of a platinum pole to which condenser discharge has been made becomes pitted to a remarkable extent, greater than when large currents are broken by separation of the poles. The sparks have therefore a high temperature. That they give rise to high gas pressure is clear from the intensity of the sound of a single spark discharge, and finally it will be shown that combustion to carbon monoxide rather than to carbon dioxide is peculiar in certain cases to ignition by capacity sparks. In addition to these the sparks are of very short duration, are oscillatory in character, and start with ionisation or breakdown of the gas between the poles. The belief that all visible sparks will ignite explosive mixtures no doubt arose from observations of the activity of condenser discharge in this respect, but while in certain cases, especially in the ignition of hydrogen, the least is in every case a well marked limit to their igniting power, and as the percentage of gas limits of inflammability are approached they require to be large. 2. The Paraffins—Ethane, Propane, and Butane .—The gases used in the present work were from the same stocks as those used for break-spark ignition. The results obtained from them are given in fig. 1. They have two interesting features; their minimum igniting current is the same in every case, in this resembling their ignition by continuous current break-sparks, but they have the parabolic form characteristic of alternating current break-spark ignition. Ethane has, however, a minimum at 7∙7 per cent., the point of combustion to carbon monoxide, the others, as before, midway between this and combustion to carbon dioxide. There is, however, on the higher side of the ethane and propane curves—the supply of butane gave out before this could be examined fully—a step or increase in difficulty of ignition corresponding to mixtures midway between four and five atoms of oxygen to one molecule of ethane, and between six and seven to one of propane. This point was thought to be some failure in the quality of the gas, but when it appeared in both, and to a still greater extent in methane, it was more fully examined. Condenser-spark ignition has therefore some of the features of both continuous and low frequency alternating current break-spark ignition, but it has a characteristic type of its own.

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On the origin of the electron emission from glowing solids

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1914.0083 ◽

1914 ◽

Vol 90 (621) ◽

pp. 548-549

Keyword(s):

Electron Emission ◽

Alternating Current ◽

Continuous Current

The electron emission from Nernst filaments has been measured under different conditions and the following results have been obtained:— 1. The electron emission from a filament heated by an alternating current is of the same magnitude as that obtained when the filament is heated by a continuous current to the same temperature.

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Chemical action that is stimulated by alternating currents

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.1914.0031 ◽

1914 ◽

Vol 90 (615) ◽

pp. 26-32

Keyword(s):

Sulphuric Acid ◽

Alternating Current ◽

The Other ◽

Chemical Action ◽

Local Circuit ◽

Low Resistance ◽

Other Hand ◽

Continuous Current ◽

Voltaic Cell

The following experiments were carried out in the year 1905. Taking a simple voltaic cell, consisting of an anode and cathode of zinc and carbon, and an electrolyte of dilute sulphuric acid, it was found that polarisation, which takes place when the cell is joined to a local circuit of low resistance, could be diminished or completely abolished, by passing through the cell an alternating current of suitable value. Fig. 1 illustrates the arrangement of the cell, D, joined up to deliver current through the ampèremeter, B; under these conditions the cell is very quickly polarised, and the continuous current falls to a very low figure. On the other hand, if a suitable strength of alternating current of. say, 100 periods per second is sent through the cell from the leads A, the cell D will be completely depolarised and will give its full current delivery. L is a self-induction and K a capacity to prevent the alternating and continuous currents from flowing in each other's circuit, the only part of the circuit common to both being through the cell.

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Effects of self-induction in an Iron cylinder when traversed by alternating currents

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1908.0031 ◽

1908 ◽

Vol 80 (539) ◽

pp. 369-378

Keyword(s):

Magnetic Induction ◽

Alternating Current ◽

Initial Position ◽

Rate Of Change ◽

Direction Parallel ◽

Zero Current ◽

In Series ◽

Continuous Current ◽

Different Depths ◽

Flow Through

In a previous paper the effects of self-induction in an iron cylinder were studied when a continuous current flowing through the cylinder in a direction parallel with its axis of figure was suddenly reversed and again maintained steady. In the experiments reported in the present paper the currents in the cylinder were made to alternate in the following manner. A continuous current dynamo, capable of giving currents up to 2000 amperes or more, was weakly excited and its brushes were short-circuited by the cylinder to be experimented upon in series with the shunt of a moving-coil ampere meter. The brushes were moved round the commutator by aid of a worm and worm-wheel from the position of maximum to that of zero current. The field was then reversed and the brushes moved back to their initial position. By continuing these operations an alternating current was caused to flow through the cylinder, and its periodic time was controlled by the speed at which the brushes were moved. The worm axle was uniformly rotated by hand at a speed determined by the operator listening to a seconds clock. Simultaneously readings were taken at known epochs on ( a ) each of three dead-beat galvanometers connected to exploring coils threaded through holes in the mass of the cylinder for the purpose of obtaining the E. M. F. 's at different depths due to the rate of change of the magnetic induction, and on ( b ) the moving-coil ampere-meter.

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