摘要:

By considering the equipotential surfaces round two equal and opposite point charges, the electric field for an infinite dielectric plate between two spherical electrodes has been calculated. The solution is given as an infinite series in terms of applied voltage, radius of the electrodes, thickness of the dielectric plate, and permittivities of the plate and the medium. Curves have been derived to show the significance of the dependence of the voltage gradient in the field on the ratio of the plate thickness to the electrode diameter, and the ratio of the permittivity of the plate to that of the medium. The edge effect in the electrical breakdown of solid dielectrics may be attributed to the discharge in the medium, which occurs when the voltage gradient on the electrode surface reaches a value favourable to its breakdown condition.

DOI:10.1049/pi-c.1962.0043

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The resolution that can be achieved in resistance measurement is shown to be limited by the amplitude of thermal noise relative to the input power of the resistance. The errors of measurement due to resolution and power loading are analysed and the minimum value of their sum is found to be proportional to the cube root of the circuit and detector noise factors, the detector bandwidth and the loadcorrection error. The noise factors of some common circuit arrangements are evaluated and the other errors of measurement in addition to resolution and power-loading errors are discussed. The total error is shown to have a limiting value near 1 part in 108for existing high-quality standard resistors and this is illustrated by a practical example.

DOI:10.1049/pi-c.1962.0044

出版商:IEE    

年代:1962

数据来源: IET

摘要:

In connection with a project for an absolute determination of the ohm, the author has developed an a.c. 4-terminal resistance bridge. This new bridge is analogous to the Kelvin double bridge, but resistive ratio arms are replaced by transformer ratio arms and inductive dividers. Besides the benefits of impedance matching and ease of amplification which the use of alternating current confers, the replacement of resistive ratios by inductive devices brings great advantages in accuracy and stability of ratio. In the bridge described here, the ratio is believed to depart from the nominal value of 10: 1 by little more than 2 parts in 107over the frequency range of 330 rad/s (52.5 c/s) to 33000 rad/s (5.25 kc/s).

DOI:10.1049/pi-c.1962.0045

出版商:IEE    

年代:1962

数据来源: IET

摘要:

High-sensitivity feedback relay amplifiers may be built with a hysteresis relay. It is possible to obtain a linear range which is not large compared with the hysteresis band. The design of these amplifiers is accomplished using the exponential input describing function. The accuracy of this design method is confirmed by experiment.

DOI:10.1049/pi-c.1962.0046

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Numerous forms of solution for the electro-thermal equations of fuses, together with various methods for establishing the parameters of these equations, have been attempted. Following earlier work on the analytical determination of the characteristics of semi-enclosed oil-immersed fuses and short fuses enclosed in silica or quartz filler, a new method has been established for the solution of long cartridge fuses. This new method is simple and based on a tabular technique derived for the work of Jaeger and Newstead on the transient heating of buried cables.The paper gives a brief treatment of the heat equations for a fuse and indicates the point of departure from the method previously adopted by Guile. The method of solution is indicated and tabular solutions are given for three particular cases of fuse elements of different cross-sections. The predicted and experimentally determined time/current characteristics are shown to be in close agreement.

DOI:10.1049/pi-c.1962.0047

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The reversal differences and non-frequency-dependent transfer errors appearing in thermal a.c.-d.c. transfer devices are known to be due to Peltier and Thomson heating. General expressions have been derived for the transfer errors due to these effects in vacuo-thermo-junctions, taking into consideration the effect of the thermal conductance due to the mid-point thermocouple. The analysis has been extended to the indirectly heated thermistor. Experimental evidence has been provided supporting the theory, and it has been shown that thermal devices having heaters of the binary alloy 80Ni 20Cr are probably free from errors due to these causes.The substantial reversal differences encountered in vacuo-thermo-junctions have been shown to be due to both Peltier and Thomson heating, combined with displacement of the temperature-sensing thermocouple from the mid-point of the heater. There is, however, no direct relationship between reversal difference and transfer error; one can exist without the other.

DOI:10.1049/pi-c.1962.0048

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper reports a study of a one-dimensional model of the interaction of an electromagnetic wave and the plasma of an ionized gas in the absence of a static magnetic field. It is shown that the reflection and transmission coefficients at the boundary of a semi-infinite plasma can be usefully discussed in terms of the Smith chart of transmission-line practice. A plasma of finite thickness is then considered, and it is found possible to avoid certain approximations that have been used in the past when plasmas with various distributions of electron density have been treated. This is achieved by carrying out the integration of the appropriate differential equations on a digital computer using quantized versions of the density and collision-frequency distributions for the electrons. This technique may be applied to plasmas with arbitrary distributions for which no analytic solutions are known. In the paper the application of the technique is restricted to certain simple distributions, namely the rectangular, triangular and half-cosine density distributions, each with a uniform distribution of collision frequency. The results for the reflection, absorption and transmission coefficients are presented graphically for a number of plasmas. Finally, the accuracy of determining the electron density from phase-bridge or interferometer measurements is discussed briefly in the light of these results.

DOI:10.1049/pi-c.1962.0049

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The Joule heating of a matrix, resulting from inelastic collisions of electrons against the hollow-pore walls, is not a uniform phenomenon but tends to concentrate on a relatively small number of particles. These preferred particles are raised in temperature much above the ambient temperature of the matrix and are accordingly subject to an accelerated rate of thermal dissociation. By suitable experimental artifices, the thermal breakdown of these particles is examined, and it is shown that they evolve oxygen gas in negative-ion form and become themselves positively charged by dissolved alkaline-earth-metal ions. Under suitably accelerated conditions, the rate of oxygen generation can become so great that the positively charged particles are blown by a propulsive gas jet from the surface of the matrix into the surrounding vacuum.

DOI:10.1049/pi-c.1962.0050

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The practically useful forms of series modulator are analysed, the results for the corresponding shunt modulators being shown to be readily derivable. The analysis of several of the circuits is carried out in a simpler manner than hitherto, and yet in all cases is sufficiently general to allow the variation of the mark/space ratio of the switching signal. It is shown that, in modulators with high impedance to unwanted products, a decrease of mark/space ratio from 1: 1 results in a decrease of conversion loss, whereas in those with correspondingly low impedance, an increase from 1: 1 results in a similar improvement. It is also shown that in the remaining cases a 1: 1 mark/space ratio gives optimum results. In every case the optimum values of terminations for the modulator for any mark/space ratio are found.

DOI:10.1049/pi-c.1962.0052

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A brief description of the underlying principles involved in vibratory power convertor systems is given, and then formulae are derived for use in system analysis and design. These consist of expressions which enable the compliance forces and effective masses of two different arrangements of conventional systems to be determined under all conditions throughout the cycle of vibration, and equations which govern the performance of the systems. Included are equations giving the deflection at which vibrating contacts open, and their optimum position along the reed has been determined. The characteristics of the systems are examined in a general analysis, and more specific details are discussed in a particular design.In a number of instances, simplification of the formulae has been undertaken and these are presented graphically. They apply as well to non-conventional systems such as single-contact transformer-vibrators or multi-contact vibrator mechanisms. The formulae are not directly limited by power considerations or by a range in dimensions for normal degrees of vibration, but they are confined in their use to systems embodying reeds of uniform rectangular cross-section. Information regarding reeds of variable cross-section is given in an Appendix.

DOI:10.1049/pi-c.1962.0053

出版商:IEE    

年代:1962

数据来源: IET