Volume 5, Issue 10, 01 October 1934
Index of content:
5(1934); http://dx.doi.org/10.1063/1.1745211View Description Hide Description
This paper presents some new methods of computing the sedimentation radius. The methods are founded on a curve for spheres, experimentally determined and constructed on the basis of the coefficient of resistance as a function of Reynolds number. When the validity of Stokes' law ceases, the sedimentation radius obtained by Stokes' formula is graphically corrected. The amount of deviation of Stokes' law from experimental data of higher Reynolds numbers has been statistically determined. Some new formulas for computing the resistance and the radius of a sphere of a given terminal settling velocity are presented.
5(1934); http://dx.doi.org/10.1063/1.1745212View Description Hide Description
The limited range of previous measurements of thermal agitation voltage is pointed out and data are given which extend the range of resistances and frequencies considerably. The results substantiate Nyquist's theory for resistances up to 1.7×109 ohms and for frequencies between 1 and 10,000 cycles per second. A value of 1.366×10−16 ergs per degree with a probable error of 0.016×10−16 ergs per degree is obtained for Boltzmann's constant. This is nearer to the accepted value than previous determinations by this method have given.
5(1934); http://dx.doi.org/10.1063/1.1745213View Description Hide Description
Hydrogen was electrolyzed into flat ring cathodes of magnetically soft iron in 0.5 N solutions of H2SO4 or of KOH. The design of the electrolytic cell permitted magnetic testing at intervals. Magnetic hardening began after many hours provided the electrolyticcurrent density was kept above a lower limit depending on the electrolyte. This hardening proceeded, at adequate current density, to an end point beyond which longer charging at any current density rarely produced any further changes in magnetic properties. Removal of hydrogen by storage in air at room temperature for 5 months, or by annealing at 400°C in vacuum for 17 hours, did not diminish the magnetic hardness produced during electrolysis. It is suggested that the iron is locally cold‐worked by non‐uniform distribution in it of hydrogen in excess of the solubility limit at room temperature, and that uniformly distributed hydrogen up to this limit has very little effect on the ferromagnetic properties.
5(1934); http://dx.doi.org/10.1063/1.1745214View Description Hide Description
The piezoelectric properties of quartz and tourmaline have been investigated through a study of the converse piezoelectric effect. In the case of quartz, the piezoelectric constant has been measured from point to point across the specimen. Considerable variation in the ``constant'' has been observed in different samples of quartz. Attention is called to difference between the motions of piezoelectric plates when subjected to static electric fields and when subjected to alternating electric fields.
5(1934); http://dx.doi.org/10.1063/1.1745216View Description Hide Description
Travel‐time curves are given for elastic waves through the earth in a region in which the velocity increases continuously with depth. These time‐distance curves have been approximated by an equation of the form X=aT 2+bT from which the velocity depth relation has been deduced. A new method for measurement of the emergence angle has been used and the values obtained agree reasonably well with those deduced from theoretical treatment of the time‐distance curve. Formulas for the travel‐time between any two points in the medium under consideration are derived. These formulas agree closely with two sets of direct measurements. In one of these the seismograph was placed at various distances directly beneath the explosion. In the second case it was placed at a fixed depth beneath the surface and the explosion was located on the surface at various distances. The approximate depth to bed rock is obtained from the time‐distance curves by use of the formulas mentioned above.