ISSN:0021-8979    

DOI:10.1063/1.1712786

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

An attempt has been made here to cover the general subject of temperature and methods of expressing temperature. The fundamental concepts involved are developed, the basis and significance of a thermodynamic scale are discussed, and the relation of various practical scales, in particular the International Temperature Scale, to the thermodynamic scale is explained.

ISSN:0021-8979    

DOI:10.1063/1.1712787

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

The fundamental laws and theories of thermoelectric phenomena and their historical development as well as the application of these phenomena to the measurement of temperature are discussed in this paper in considerable detail. Thermoelectric thermometry, with particular regard to types of thermocouples, protection of thermocouples, fundamental considerations in temperature measurements, etc. are treated primarily from the practical standpoint.

ISSN:0021-8979    

DOI:10.1063/1.1712788

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712789

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712790

出版商:AIP    

年代:1940

数据来源: AIP

摘要:

The Townsend equation for the passage of a spark is analyzed and its inadequacy for explaining sparks in air at near atmospheric pressures is demonstrated. The mechanisms active in air at higher pressures,viz., the electron avalanche and its tip field, photo‐ionization in the gas and positive streamer formation are presented. A quantitative criterion for streamer formation is applied to give a quantitative theory for spark breakdown in air at atmospheric pressures. The theory gives quantitative agreement with experiment and predicts departures from Paschen's law. At values of the product, pressure times gap length less than 200 mm×cm in air, the new mechanism is unimportant. The theory is applied to longer sparks at atmospheric pressures and the effect of the decrease in density of photo‐ionization in longer avalanches considered. This leads to a modification of the Meek mechanism by which the electron avalanche slows down while a retrograde positive streamer moves at high speed to the cathode and then advances again. This mechanism enables one to discuss the breakdown potentials of unsymmetrical gaps showing the difference in sparking potential between positive and negative points. The mechanism is correlated with the passage of lightning discharges. Alterations of Meek's theory of the stepped leader are indicated. Part I describes the classical theory of spark discharge and the nature of the mechanism which must be active at higher pressures. Part II will consider streamer formation and spark breakdown in short and long gaps.

ISSN:0021-8979    

DOI:10.1063/1.1712792

出版商:AIP    

年代:1940

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712793

出版商:AIP    

年代:1940

数据来源: AIP