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1 Dec 1931

Volume 1, Issue 6, pp. 343-422


SOME EXPERIMENTS WITH GAS‐FILLED Cs☒O☒Ag PHOTO CELLS

K. H. Kingdon and H. E. Thomson

Physics 1, 343 (1931); http://dx.doi.org/10.1063/1.1745013 (9 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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The amplification of the cathode emission by argon is much greater for a tube with a photo‐cathode, than for a tube of similar geometry equipped with a thermionic cathode. This difference is attributed to large secondary electron emission by positive ion bombardment of the photo‐cathode. If the anode voltage of one of these argon‐filled tubes is abruptly increased, the time lag in the resulting current change is of the order 5×10−5 sec. for the thermionic tube, but of the order 10−3 sec. for the photo‐tube. This lag is attributed to the life of the positive ion charge on the spongy surface of the photo‐cathode. Measurements of the spontaneous fluctuations in the current through a gas‐filled photo‐tube indicate that the ``noise'' is of low frequency and associated with the gas amplification effect.

THE USE OF GLYCOL‐PHTHALIC ANHYDRIDE RESIN AS A HIGH‐VACUUM CEMENT

T. P. Sager and R. G. Kennedy

Physics 1, 352 (1931); http://dx.doi.org/10.1063/1.1745014 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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By using ethylene glycol‐phthalic anhydride resin to seal the top of a camera box in a magnetic spectrograph it was found that a high vacuum could be obtained after pumping a short time. The preparation of the resin and its characteristics are described.

THE TIME LAG OF THE ELECTRIC SPARK

John A. Tiedeman

Physics 1, 354 (1931); http://dx.doi.org/10.1063/1.1745015 (12 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The variation in the time lag of the electric spark has been investigated as a function of the applied field and the number of electrons liberated at the cathode by ultraviolet light, during the application of the field. The time intervals were measured by a Lichtenberg figure method with a precision of 5×10−10 sec. A biasing positive potential was applied to the zinc cathode in such a way that not only were the residual ions removed from between the electrodes before the application of the field but a known number of electrons could be liberated from the cathode by ultraviolet light while the field was applied. For the case of air, hydrogen, and nitrogen curves are given showing how the time lag decreases with an increase in the number of electrons liberated during the application of the field. It is shown that with comparatively high applied fields the time lag reduces to approximately the time required for an electron to be liberated in the gap.

A NEW METHOD OF DIELECTRIC CONSTANT MEASUREMENT AT RADIO FREQUENCIES

H. L. Andrews

Physics 1, 366 (1931); http://dx.doi.org/10.1063/1.1745016 (14 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A new method of making dielectric constant measurements on gases at radio frequencies is described. This method eliminates the difficult condenser calibration required by earlier heterodyne methods. In addition, the effect of certain errors in previous methods can be estimated. The dielectric constant is obtained in terms of a single frequency standard, whose absolute frequency can be determined by auxiliary apparatus described. The method has been used to measure the dielectric constant of nitrogen at room temperature over a pressure range from zero to seven atmospheres. All measurements were made at a frequency of 884 kilocycles. The final value of ϵ−1 at N.P.T.=0.000589 is probably correct in absolute value to better than 0.5 percent.

CHARTS FOR TRANSMISSION LINE PROBLEMS

H. E. Hartig

Physics 1, 380 (1931); http://dx.doi.org/10.1063/1.1745017 (8 pages)

Online Publication Date: 29 December 2004

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Charts to a reduced scale are presented from which it is possible to determine with very little labor the vector voltage, current and impedance at any point of a transmission line with given terminations. Examples are given exhibiting the properties of the charts and the method of use, illustrating how without computation the variation of E, I and Z from one end of the line to the other may be visualized. The charts are chiefly useful for visualizing the electrical conditions on lines which are electrically long, that is, telephone or radio transmission lines.

A ``MAGNETIC SHARPENER''

L. W. McKeehan

Physics 1, 388 (1931); http://dx.doi.org/10.1063/1.1745018 (5 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The claim that the mere placing of a double‐edged safety razor blade upon the poles of a specially designed permanent magnet has a sharpening action has been investigated by studying the characteristics of the device and by testing the sharpness of blades so treated in comparison with untreated and with mechanically stropped blades. No definite ``magnetic sharpening'' was observed to occur in these tests.

THIXOTROPY OF LITHARGE AND GLYCERINE

E. Karrer and P. Wasserman

Physics 1, 393 (1931); http://dx.doi.org/10.1063/1.1745019 (14 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Thixotropy may be defined as change in viscosity; or as change in the hardness of the solid state, after mechanical agitation. Rate of hardening decreases with increase of glycerine (critical point near 32 percent). Rate of hardening increases with rise of temperature. Water accelerates rate of hardening. Acids increase, bases decrease rate of hardening in general. Samples of litharge and of glycerine vary greatly because of differences in particle size, in composition, and particularly amount of moisture.

THE THERMO‐STROMUHR METHOD OF MEASURING BLOOD FLOW

J. F. Herrick and Edward J. Baldes

Physics 1, 407 (1931); http://dx.doi.org/10.1063/1.1745020 (11 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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The purpose of the following article is to bring to the attention of the physicist, who is interested in the application of physics to physiology, a typical problem in biophysics. Rein, a physicist at the University of Freiburg, was confronted with the necessity of knowing accurately the blood supply to a certain organ. Because the various standard methods proved inadequate he developed an ingenious method which he calls the thermo‐stromuhr. This method of determining blood flow has been modified in two respects: in the method of measuring the heating energy applied to the blood vessel, and in the method of construction of the diathermy‐thermoelements. A tuned circuit is used which permits the measurement of resistance by the method of substitution. The diathermy‐thermoelements are made from transparent bakelite and the process of construction is fully described. The theory of the thermo‐stromuhr as well as the experimental application is explained in detail.
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THE EDITOR'S COLUMN

Physics 1, 418 (1931); http://dx.doi.org/10.1063/1.1745021 (4 pages)

Online Publication Date: 29 December 2004

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ERRATA: AN ELECTROMAGNETICALLY CONTROLLED THREE‐ELECTRODE VACUUM TUBE

F. B. Haynes

Physics 1, 422 (1931); http://dx.doi.org/10.1063/1.1745022 (1 page)

Online Publication Date: 29 December 2004

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