摘要:

A brief summary is given of the steps in the development of the thermionic vacuum tube. This leads back to the experiments of various people in the early 1880's, and particularly to the attempts by Thomas A. Edison to find the cause of the blackening of his newly developed incandescent lamps. Edison discovered during this work that substantial electric currents could flow between a hot carbon filament and another electrode across a high vacuum. Along with his contemporaries he wrongly ascribed the current to the flow of molecular ions rather than electrons. He, nevertheless, invented and built devices making use of these currents, the first applications of thermionics. The work received wide publicity at the time. Extracts from Edison's notebooks and other sources serve as illustrations.

ISSN:0002-9505    

DOI:10.1119/1.1935997

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Procedures and inexpensive apparatus are described for photographing and projecting patterns formed by crystals in convergent polarized light. The methods are especially suitable for wide-angle patterns such as those formed by mica. Illustrations are given.

ISSN:0002-9505    

DOI:10.1119/1.1935998

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1935999

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Two questions are discussed. The first asks whether experiments on accelerated systems (e.g., red-shifts produced in rotating disks) can serve to verify the general theory of relativity. The answer is “no.” The second asks to what extent the special theory of relativity and the principle of equivalence determine the well-known effects of the general theory of relativity. It is important to formulate this question very carefully because special relativity and the equivalence principle do not form a consistent theoretical system. If this is done, then the answer is that the equivalence principle leads to the same gravitational red-shift as general relativity but does not lead to specific values for the bending of light rays by a star or for the perihelion rotation of a planetary orbit.

ISSN:0002-9505    

DOI:10.1119/1.1936000

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

A simplified development of Carathéodory's thermodynamics, which obviates the principal mathematical complications of the original paper, is presented. A sketch of Carathéodory's treatment is given in an Appendix.

ISSN:0002-9505    

DOI:10.1119/1.1936001

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Although most physics instructors agree that the analysis of error in a measurement is equally as important as the measurement itself, the matter is often neglected in the introductory laboratory. This neglect is frequently attributed to the belief that the relevant equations lie beyond the comprehension of the students. An elementary treatment of error is here presented in which it is shown that, at least in measurements involving simple functions, the propagation of error can be discussed using simple algebra. Two experiments are described as a basis for discussion.

ISSN:0002-9505    

DOI:10.1119/1.1936002

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Questionnaires on laboratory instruction were mailed to 1000 colleges in the U. S. A. Frequency distributions of the 500 returns are given for length of laboratory period, instructional methods, evaluation techniques, enrollments, and pressing teaching problems. Separate analyses are made for schools offering a physics major and those not offering it.

ISSN:0002-9505    

DOI:10.1119/1.1936003

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

A continuous flow-type mechanical equivalent of heat apparatus is described. It consists of two turbines immersed in water and rotated with respect to each other by an electric motor. Lucite housing facilitates observation of the energy conversion and provides good thermal insulation. In our elementary physics laboratories, most students obtain results within 2% of the accepted value.

ISSN:0002-9505    

DOI:10.1119/1.1936004

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

It is shown that a perfect gas must be defined by two independent statements. BesidesPV = nRT, either(δE/δV)T = 0orT = θmay be used. The proof shows that the second law will not yield(δE/δV)T = 0fromPV = nRTalone, and is given for both the Carnot cycle and Carathéodory formulations of the second law.

ISSN:0002-9505    

DOI:10.1119/1.1936005

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

A simple “scissorlike” effect is mathematically examined as a measurable process that can produce over-light speeds of the intersectional point. This process is studied under the conditions of restricted relativity theory, and it is shown that when the intersectional point exceeds light speedcin one inertial systemS, it can undergo “temporal reversal” relative to some other inertial systemS′.

ISSN:0002-9505    

DOI:10.1119/1.1936006

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP