Volume 12, Issue 12, 01 December 1941
Index of content:
12(1941); http://dx.doi.org/10.1063/1.1712874View Description Hide Description
THIS chapter presents theories of liquidviscosity, particularly those of van der Waals, Andrade, Prandtl, and Eyring. Whereas the viscosity of gases is based on the collisions of molecules, that of liquids is dominated chiefly by molecular attraction forces. Experimental material is presented on the effect of chemical constitution, temperature, pressure, and mixture ratio on viscosity, which effect is explained on the basis of existing theories. A brief outline of turbulent flow closes the chapter.
12(1941); http://dx.doi.org/10.1063/1.1712876View Description Hide Description
This paper describes the electrical characteristics of gas‐filled discharge tubes when flashed by a condenser discharge. The object of the experiments was to determine the effects of tube dimensions, pressure, voltage, and capacity upon the performance. The results are of an experimental nature and cover a limited range of values of tubes and circuit constants. An empirical constant called tube resistance is defined and evaluated. This constant is useful in predicting the performance of tubes in electrical circuits.
12(1941); http://dx.doi.org/10.1063/1.1712877View Description Hide Description
A theoretical discussion is presented of the transmission of electromagnetic waves of the symmetrical, transverse magnetic type by a space charge of uniform density, rotating under the influence of a uniform magnetic field. It is shown that the space charge presents to the wave an effective dielectric constant less than unity. By appropriate choices of magnetic field, the dielectric constant can be reduced to zero and can even become negative, so that the wave undergoes attenuation as it passes through the space charge. Experiments are described on the control of the propagation constants of 470‐megacycle waves by variation of the dielectric constant of the rotating space charge medium. The results obtained are in agreement with the theoretical predictions.
12(1941); http://dx.doi.org/10.1063/1.1712878View Description Hide Description
In ferromagnetic materials if the magnitude and direction of the magnetic field intensity are changed hysteresis occurs. This, in general, is of two types: the usual alternating hysteresis, and the torque component of hysteresis which gives rise to the rotational loss when the direction of the magnetic field intensity is changed and the magnitude is held fixed. By means of a torquemagnetometer, the time average of the torque has been observed as a function of the applied magnetic field intensity for elliptical fields of different eccentricity. For the siliconiron disk investigated, and with the field along one axis (the first axis) as a parameter, the time average of the torque increases with applied field along the mutually perpendicular axis, reaching a maximum value at the bend in the magnetization curve and then decreases as saturation is approached. The torque curves first increase, go through a limiting curve, and then decrease as the field along the first axis is increased. A qualitative explanation of the shape and variation of the torque curves with field strength is suggested.
12(1941); http://dx.doi.org/10.1063/1.1712879View Description Hide Description
The general characteristics of response curves of one degree of freedom systems excited by constant force amplitudes and amplitudes increasing with the square of the exciting frequency are discussed. Relations between displacement, velocity, power‐input and phase angle versus discord are compared for various damping values. Simple formulae are derived to determine by means of these response curves the static and dynamic constants of mechanical systems with one degree of freedom. A numerical example demonstrates the practical application.