摘要:

Simple formulas are developed for the impedance of short lengths of Lecher system terminated by resistances. This impedance is most simply expressible as a multiple of the surge impedance. The variation of impedance with system length is traced and certain simple relationships are found. It is shown that any system of loads across a Lecher system is equivalent to a certain length of system terminated by a certain resistance. The formulas account for Takagishi's double hump phenomenon and this phenomenon is applied to finding the bridge shortening of an actual bridge. A method of calculating resistance from a resonance curve is derived.

ISSN:0021-8979    

DOI:10.1063/1.1745024

出版商:AIP    

年代:1932

数据来源: AIP

摘要:

Measurements are reported on the color sensitivities of various photoelectric tubes having cathodes made of alkali metals. A composite surface of R‐Ag‐RO‐Ag of any alkali metal R shows a higher sensitivity over a wider range of wave‐lengths than R‐RO‐Ag and has two peaks, one between 330 and 370 m&mgr;, and one at about 500 m&mgr; for potassium and 550 m&mgr; for rubidium and between 700 and 800 m&mgr; for caesium. If a gas filled lamp at 2700°K is used as a light source, photoelectric currents from vacuum photo‐tubes are obtained sometimes as large as 29&mgr;a per lumen for potassium, and 10–15&mgr;a per lumen for rubidium, and 40–50&mgr;a per lumen for caesium. It is also reported that the potassium cell in combination with a proper filter would constitute a means for an ideal photometer.

ISSN:0021-8979    

DOI:10.1063/1.1745023

出版商:AIP    

年代:1932

数据来源: AIP

摘要:

1.Electrokinetic studies of aqueous solutions of sodium formate, sodium acetate, sodium propionate, sodium butyrate, sodium caprylate, sodium oleate and sodium oxalate have been conducted at a cellulose interface with the streaming potential technique.2.It is suggested that in interest of clearness and accuracy the attempt to express electrokinetic data in terms of ``potentials'' be abandoned and that the electric moment of the double layer, which does not require a knowledge of the magnitude of the dielectric constant, be substituted for &zgr;.3.It is indicated that after the fourth carbon atom has been added the electric moment of the double layer is essentially a constant.4.It is noted that there is no correspondence between the ionization constant of the fatty acid from which the soap is derived and its effect on the electrokinetic conditions at the interface. This indicates that hydrolysis and the resulting OH ion plays a minor role.5.It is pointed out that the electric moment of the double layer in the case of the longer chained soaps is almost independent of the concentration whereas that of the short chained soaps are much more sensitive to increased concentration.6.The maximum electric moment is found at about 2×10−4normal. This is true also for a number of salts.

ISSN:0021-8979    

DOI:10.1063/1.1745025

出版商:AIP    

年代:1932

数据来源: AIP

摘要:

The magnetic susceptibilities of eight series of alloys: tin‐thallium, antimony‐thallium, thallium‐cadmium, zinc‐cadmium, lead‐antimony, tin‐antimony, cadmium‐antimony and zinc‐antimony have been investigated by Gouy's method. In three series,—antimony‐cadmium, antimony‐zinc and tin‐antimony an intermetallic compound is indicated by an abrupt change in the slope of the susceptibility concentration curve. The compounds thus indicated are SnSb, CdSb, and ZnSb with some evidence for the compound Sn2Tl. There is nearly a linear relation between the susceptibility and the concentration of one of the constituents where the constituents form simple heterogeneous mixtures—a result best illustrated in the zinc‐antimony series of alloys.

ISSN:0021-8979    

DOI:10.1063/1.1745026

出版商:AIP    

年代:1932

数据来源: AIP

摘要:

The output voltageepof a thermionic tube operated over a suitable restricted range of grid voltagesegmay be represented by the parabolaep=b0+b1eg+b2eg2. By adding to this in opposite phase the output of another tube, operated on the straight line portion of its curve, we may balance out entirely the termb1eg, so that the characteristic of the combination of tubes isec=b0+b2eg2. The system will then operate as a frequency doubler, for the output is proportional toeg2alone. In the experimental set‐up described, with a 201A tube, an output of 0.175 volts of frequency 2fis obtained from an input of 1.0 volts of frequencyf. It is found that when the characteristic of the system is plotted, the curve is never a symmetrical parabolaec=b0+b2eg2over a very wide range of grid voltages. This is because the coefficient of the cube term in the equation of the tube characteristic is not negligibly small, and the equation must be writtenec=b0+b2eg2+b3eg3. It is shown how the coefficientb3may be determined by measuring the dissymmetry of the curve.

ISSN:0021-8979    

DOI:10.1063/1.1745027

出版商:AIP    

年代:1932

数据来源: AIP

摘要:

An apparatus is described for the class‐room demonstration of electron diffraction photographs obtained from thin metallic films and using the range 2000 to 15000 volts. It is very simple to build and reasonably stable. The method of operation is explained.

ISSN:0021-8979    

DOI:10.1063/1.1745028

出版商:AIP    

年代:1932

数据来源: AIP

摘要:

An experimental comparison has been made of three methods of measuring the unpolarized resistivity of glass and fused quartz over a temperature range from 20 to 500°C. At high temperatures all three methods are in quantitative agreement and give a straight line when the logarithm of the resistivity is plotted against the reciprocal of the absolute temperature. At lower temperatures, however, the a.c. curve deviates from this straight line, indicating an additional component of loss which does not exist on d.c. This additional loss may be due to the orientation of polar molecules, though no definite proof can be given. The results obtained by the other two methods, both with direct current, are in close agreement over the whole temperature range, and give without doubt the true unpolarized resistivity.

ISSN:0021-8979    

DOI:10.1063/1.1745029

出版商:AIP    

年代:1932

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1745030

出版商:AIP    

年代:1932

数据来源: AIP