摘要:

A convenient circuit for making linear measurements of high resistances and low capacitances consists of a conventional power supply, a relaxation oscillator, and a flip-flop circuit for alternately connecting and disconnecting a seconds timer. The relaxation oscillator makes use of the WL 759 cold-cathode, glow-discharge tube.

ISSN:0002-9505    

DOI:10.1119/1.1934118

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

Nonrelativistic explanations for the advance of Mercury's perihelion are described, and the point made that Einstein's theory is favored over these because of his theory's intellectual appeal. Consideration is given to the possibility that the perihelion advance could be explained by hypothesizing a charge on the Sun which induces a dipole on Mercury and thereby causes a departure, from inverse square, of the total force between the Sun and Mercury. It is shown that such a hypothesis runs into serious difficulties. The results of the calculations are thought to be illustrative of the difficulties which are encountered by an attempt to account for the advance by postulating heretofore unsuspected interactions between Mercury and other bodies.

ISSN:0002-9505    

DOI:10.1119/1.1934119

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

Attention is called to the usefulness of the Doppler effect in introducing the idea of invariance with respect to coordinate transformation. The invariant property of the phase of a sound wave with respect to Galilean transformation is applied to several Doppler effects including that resulting from transverse motion of source and detector in a moving medium.

ISSN:0002-9505    

DOI:10.1119/1.1934120

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

Demonstrations of standing microwaves in helices are described for helix circumferences ranging from 0.1 to 3 wavelengths. Special attention is given to dimensions of helices used in (1) traveling wave tubes as broad band amplifiers, (2) axial mode antennas for producing a circularly polarized axial beam, and (3) radial mode antennas for broadcasting a horizontally polarized radial beam. The demonstrations are made with 2450 megacycle/sec educational equipment.

ISSN:0002-9505    

DOI:10.1119/1.1934121

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

An argument is presented by which the velocity equation for sound waves in a gas is obtained as a result of equating the kinetic and potential energies per unit volume at the same time and position in the wave train.

ISSN:0002-9505    

DOI:10.1119/1.1934123

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

In the electromagnetic theory one hears of gauge invariance and the difficulties that result from this. Similar obstacles arise in the general theory of relativity because of the coordinate covariance requirement. The actual nature of the effect of the invariance stipulations is usually not clearly understood because the theories investigated are themselves rather complicated. However, it is possible to pick a simple enough example so that one can clearly see the effect of invariance requirements. It is the purpose of this paper to pick a central problem of geometrical optics and to show what happens as a result of the parameter covariance.

ISSN:0002-9505    

DOI:10.1119/1.1934124

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

The magnificent metal doors of Imperial Chemical House, Millbank, London, deserve to be better known to physics teachers than they are. They are faced by six cast panels illustrating the evolution of civilization as a result of scientific discoveries. Two of these panels are here reproduced and discussed.

ISSN:0002-9505    

DOI:10.1119/1.1934125

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

Three forms of an instrument which combines the functions of the absolute electrometer and the current balance are described. The theory of this instrument and its application in determining current, potential, and resistance in the intermediate course in electricity and magnetism are discussed briefly.

ISSN:0002-9505    

DOI:10.1119/1.1934126

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

Orthodox courses and textbooks in elementary physics are criticized for too much material, too little interrelation to other disciplines, too much emphasis on practical applications, too little modern physics, and too little opportunity for student initiative. The selective rather than general approach is briefly reviewed, and a course described which is part of the Directed Studies in the Liberal Arts at Yale, an experiment in a prescribed curriculum for the first two years.Elementary Atomic Physics, with no prerequisites, devotes the first term to a background in classical physics centered around particle dynamics and electrodynamics, and the second term to atomic and nuclear physics. General reaction appears favorable, and screening students according to backgrounds, introducing seminars with opportunities for laboratory experiments, and integrating physics more closely with other courses are suggested improvements.

ISSN:0002-9505    

DOI:10.1119/1.1934127

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

A commercial electrostatic speaker is now available that provides an excellent and cheap line source of high-frequency sound in the 1000 cps to 20 000 cps range. It can also be operated in reverse to act as a quite satisfactory detector at these frequencies. By replacing the Galton whistle with one of these speakers, and using a second speaker as a detector, the Schilling apparatus can be used for quantitative undergraduate experiments on interference and diffraction, yielding results to better than 2% accuracy.

ISSN:0002-9505    

DOI:10.1119/1.1934128

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP