ISSN:0002-9505    

DOI:10.1119/1.10962

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10963

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

A commerical magnetic stirrer provides a convenient rotating horseshoe magnet for several well‐known demonstrations of induced eddy currents and Lenz’s law such as the spinning of a nonferromagnetic metal top or coin and the operation of a speedometer. A new demonstration is paradoxical: A steel ball rolls in a circle either in the same direction as the rotation of the stirrer magnet or in the opposite direction. That an aluminum cone or rivet also rolls in the opposite direction shows that the latter effect is due to induced currents, but this seems to violate Lenz’s law.

ISSN:0002-9505    

DOI:10.1119/1.10964

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

The contest entry was a spring‐coupled triple pendulum. It was used to demonstrate the character of normal modes and in particular a mode that has highQeven with the center pendulum highly damped. The coupling of one of the springs to a pair of pendulums could be varied while they were swinging and with this adiabaticity in the effect upon a normal mode was observed. In the discussion the mathematical simularity to the equations of three coupled quantum mechanical levels is pointed out. The eigenstate in metastable hydrogen atoms that survives passage through the spin filter of a polarized ion source is compared to the high‐Qmode observed in the triple pendulum.

ISSN:0002-9505    

DOI:10.1119/1.10965

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

By making a holograph of a holograph, one can produce a picture in which the virtual image of a lens appears in front of a photographic plate while the images of various objects appear in or behind the plate. This virtual image of the lens has all the properties of an acutal lens when viewing these objects. It will even act as a real thin lens in combination with other real lenses.

ISSN:0002-9505    

DOI:10.1119/1.10966

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

A device that utilizes rollers to generate two‐dimensional random motion is described. Quiet, rugged, and versatile, it is suitable for illustrating a wide variety of molecular phenomena. Three specific uses are presented in detail.

ISSN:0002-9505    

DOI:10.1119/1.10967

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

Prepared at the request of the AAPT Editorial Board for Resource Letters. This is one of a series of Resource Letters on different topics intended to guide college physicists, astronomers, and other scientists to some of the literature and other teaching aids that may help improve course contents in specified fields. No Resource Letter is meant to be exhaustive and complete; in time there may be more than one Letter on some of the main subjects of interest. Comments on these materials as well as suggestions for future topics will be welcomed. Please send such communications to Professor Aaron Owens, Editor, Resource Letter Board, Department of Physics, Kenyon College, Gambier, Ohio 432022.Notation: The letter E after an item number indicates elementary level; the letter I indicates intermediate level; and the letter A indicates advanced material. An asterisk (*) indicates those references we feel to be especially helpful.Reprints: When ordering, request Resource Letter WI‐1. Enclose $0.75 per copy (not in stamps) together with a stamped, self‐addressed envelope and send to Publications Department, American Association of Physics Teachers, Graduate Physics Building, SUNY at Stony Brook, Stony Brook, New York 11794.

ISSN:0002-9505    

DOI:10.1119/1.10968

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

Einstein’s seminal paper on the special relativity theory of 1905 ’’On the Electrodynamics of Moving Bodies’’ is discussed in its historic context. It is shown how different was Einstein’s approach to the electrodynamics of moving bodies from that of a major research effort which attempted to deduce all of physics from H. A. Lorentz’s electromagnetic field theory—the electromagnetic world picture.

ISSN:0002-9505    

DOI:10.1119/1.10969

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

The history of nuclear reactors gives us a singular opportunity to study what happens when the world’s leading physicists, faced with the same problem, find solutions in complete isolation from one another. This paper takes as an example an elementary part of reactor theory, the four‐factor formula. It was discovered independently at least six times (in France, Germany, the Soviet Union, and the United States). But the groups, separated by wartime secrecy, used the formula in very different ways. Usually it was simply ignored. In only two cases was the formula integrated with experimental work—by the French and, in an entirely different way, by Fermi’s team in Chicago. Thus even though simultaneous discovery occurred, we need not conclude that the physics developed inevitably in a unique pattern.

ISSN:0002-9505    

DOI:10.1119/1.10970

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP

摘要:

The ability to amplify by means of a semiconductor device can now be clearly seen as the foundation stone of modern electronics, but such clarity of vision was not generally evident in the years immediately following the invention of the transistor. That few should have predicted the future with accuracy is hardly remarkable, but what is of interest is that many seem to have viewed the new transistor only as a possible substitute for the old vacuum tube. Despite radical differences and new possibilities, many chose to see only the similarities between tube and transistor. In the present paper, we explore some of the origins and consequences of this attitude.

ISSN:0002-9505    

DOI:10.1119/1.10971

出版商:American Association of Physics Teachers    

年代:1977

数据来源: AIP