Volume 9, Issue 3, 01 March 1938
Index of content:
9(1938); http://dx.doi.org/10.1063/1.1710402View Description Hide Description
9(1938); http://dx.doi.org/10.1063/1.1710403View Description Hide Description
9(1938); http://dx.doi.org/10.1063/1.1710407View Description Hide Description
9(1938); http://dx.doi.org/10.1063/1.1710408View Description Hide Description
Magnetic torque measurements offer a possibility of specifying texture in ferromagnetic materials in a quantitative fashion and several methods have been proposed for accomplishing this. The method of Akulov and Brüchatov, although formally correct, is shown to be so restricted by its assumptions as to be inapplicable even to the commonest texture. A method proposed by Bitter, involving root‐mean‐square deviations from some mean orientation, is found to fail in practice because of the uncertainty in the measurement of the magnetic energy. A modification of this method, in which x‐ray data are used to establish a relationship between two of the root‐mean‐square deviations, gives results in fair agreement with the pole figure of a cold‐rolled iron‐silicon alloy.
9(1938); http://dx.doi.org/10.1063/1.1710409View Description Hide Description
It is shown that the invariant field equations of Maxwell for stationary bodies are also valid for accelerated bodies, if all ordinary differentiations are replaced by absolute differentiation. The affine connection Γγ αβ appearing in the absolute derivatives refers to a general non‐Riemannian metric space, with a holonomic or nonholonomic reference frame. The field equations are in a more general form than those used in the five‐dimensional unified field theory and reduce to the latter as a special case. However, the presence of an electrostatic field is not assumed in this paper. The motion of an accelerated body possessing mass, electric current and magnetic flux is given by an extended form of the dynamical equations of Lagrange containing the same general affine connection as the field equations. The material terms of the dynamical equations are expressed by a mechanical impulse‐energy tensor and the resultant motion of the material body under the influence of an electromagnetic field and a mechanical force is expressed by a combined impulse‐energy equation. The equations are calculated for a representative rotating electrical machine used in industry.
9(1938); http://dx.doi.org/10.1063/1.1710410View Description Hide Description
Candescence and nigrescence curves are shown for a number of tungsten lamps, vacuum and gas‐filled, ranging in size from the automobile lamps up to the 30‐volt, 30‐ampere lamp and the 1000‐watt photoflood lamp. Data are given for similar filaments mounted in vacuum lamps and in lamps filled with argon, nitrogen, hydrogen, and helium. The filament of a vacuum lamp reaches 90 percent brightness on heating in time t=0.060I 0.54; 10 percent brightness on cooling in time t=0.022I 0.70; for gas‐filled lamps, t=0.15I 0.70 and t=0.070I 0.70, respectively. (I is the normal operating current of the lamp.) The percent of total variation, P, in brightness during a cycle for a vacuum lamp on 60‐cycle a.c. is P=34D −1.06, on 25‐cycle a.c., P=28D −1.37; for a gas‐filled lamp, P=75D −0.89 and P=63D −0.91, respectively. (D is the filament diameter in mils.)