Volume 4, Issue 7, 01 July 1933
Index of content:
4(1933); http://dx.doi.org/10.1063/1.1745186View Description Hide Description
It is shown that a negative resistance of a definite value, introduced into the plate circuit of a thermionic valvetheoretically allows the voltage sensitivity to become infinite. Practical application is made to construct high sensitivity direct‐current amplifiers. The data show a mutual conductance of 30,000 microamp. per volt.
4(1933); http://dx.doi.org/10.1063/1.1745187View Description Hide Description
A study is made to determine the way in which the frequency of the pliodynatron oscillator depends upon the plate and control‐grid voltages. The optimum operating voltages for greatest constancy of frequency are discussed. A new theoretical expression for the frequency of this oscillator is derived. The theoretical frequency variation with plate voltage is shown to be closely in agreement with the experimental variation.
4(1933); http://dx.doi.org/10.1063/1.1745188View Description Hide Description
The object of this experimental investigation was to determine the nature of the valve effect. After the description of the valve some characteristic and photometric curves are given. Sensitivity curves are then described which show the relation between the wave‐length and the photoelectric current per unit of light energy. These curves show distinct maxima, like ordinary photoelectric cells; this character of the sensitivity curves support the theory that the effect is primarily a photoelectric phenomenon connected with space charges. Other assumptions are shown to be untenable. Some additional phenomena, expecially of the dark current, and experiments with various modifications of the valve are reported.
4(1933); http://dx.doi.org/10.1063/1.1745189View Description Hide Description
Neither the diffusionaltheory of Maxwell nor the convectional theory of August is capable of representing adequately the processes of evaporation and heat transfer occurring at the wet bulb. An examination of these processes with the aid of the Reynolds analogy between heat and vapor transfer by convection on one hand, and fluid friction on the other, indicates that the correct theory consists of a combination of the two older theories, in which a mechanism of convection plus conduction is postulated for both heat and vapor transfer. When the thermal diffusivity is equal to the material diffusivity, a special case occurs, for which all three theories give the same result. This condition is approximately satisfied for the case of water evaporating into air; other gases or liquids must therefore be used to discriminate among the various theories. Experiments with water and four organic liquids show that the new theory represents the facts very accurately, and may be made the basis of a sound system for the reduction of psychrometric observations.
4(1933); http://dx.doi.org/10.1063/1.1745190View Description Hide Description