摘要:

Traditional methods used to teach physics to students who are physics or engineering majors are inappropriate for introductory, ‘‘science literacy’’ courses. We describe here an alternative ‘‘top‐down’’ teaching method which has been used successfully to enhance such a course given at the University of Auckland in New Zealand. The approach reverses the traditional sequence of instruction and is based on beginning all lecture treatments with discussions of complex, yet familiar phenomena and working backward to discussions of the simple physical laws underlying them. We make extensive use of demonstrations and give examples of the particular application of this method to the teaching of electronics. The advantages and problems of this approach compared to traditional teaching methods in physics are also discussed.

ISSN:0002-9505    

DOI:10.1119/1.18257

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The quest to find faster‐than‐light particles has intrigued physicists for decades, though it has yet to turn up any real candidates. Even if a superluminal universe does exist, we have no way to reach it given that we must go through the speed of light, which to the best of our knowledge is impossible. In this paper, I show that by making speed complex, we can go around the speed of light in a manner analogous to the way a car faced with an infinitely tall road block might leave the road to go around that barrier. The treatment is a mathematical device; no known physical interpretation exists for the imaginary part of a complex speed. However, it can provide an entertaining problem in special relativity, one that may encourage students to think about the connections between equations and the physical universe.

ISSN:0002-9505    

DOI:10.1119/1.18258

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

A simple prescription is given for determining the degeneracy of any energy level of the spherical well, harmonic oscillator, or hydrogen atom in arbitrary spatial dimension.

ISSN:0002-9505    

DOI:10.1119/1.18185

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

We present a model calculation of the acceleration of gravity in an ellipsoidal mass with nonuniform density. Using parameters resembling that of the earth’s dimensions and mass density, we are able to account for most of the observed variation of the acceleration of gravity at the pole and the equator which is not related to rotational effects. The nonuniformity of the density of mass, when considered with the ellipsoidal flattening of the earth, is one of the most important factors to be considered when explaining the difference of the acceleration of gravity at the pole and equator. A simple model of a flattened earth with a uniform mass density does not give a reasonable explanation for this variation of the gravitational acceleration.

ISSN:0002-9505    

DOI:10.1119/1.18186

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The measured length distributions of slidings of solid cylinders of aluminum, brass, teflon, and polyvinyl chloride on an incline obey nontrivial scaling laws. No significant dependence of the scaling exponent on material is observed and the data obtained are in agreement with the Gutenberg–Richter law for the distribution of earthquakes and with numerical simulations exhibiting self‐organized criticality made by Chen, Bak, and Obukhov [Phys. Rev. A43, 625–630 (1991)].

ISSN:0002-9505    

DOI:10.1119/1.18187

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The classical and quantum mechanical problem of a particle in the infinite circular well has recently surfaced in two quite different manifestations: (i) the observation of ‘‘electron standing waves’’ in circular ‘‘corrals’’ of atoms adsorbed on surfaces and (ii) as a benchmark example of an integrable system for comparison to the classical and quantum chaotic behavior of the ‘‘stadium billiards’’ problem. Motivated by this, we review the quantum and classical probability distributions for both position and momentum for this familiar problem, focusing on the visualization of the quantum wave functions and classical trajectories as well as the semiclassical connections between the two.

ISSN:0002-9505    

DOI:10.1119/1.18188

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

A simple turntable and a simple spring gun mounted on it demonstrate the angular momentum conservation principle by providing independent measurements of the angular momenta of the turntable, and of a metal ball, projected horizontally—and tangentially—from the spring gun.

ISSN:0002-9505    

DOI:10.1119/1.18189

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

After several years of trial and error, I have developed a method to generate consistently good library research papers in undergraduate science classes, papers that show thought and integrate information. It is based, in part, on treating the student papers as journal article submissions. There are five steps to the procedure which are spaced throughout the semester to ensure that the papers will not be done at the last minute. The steps are: (1) selecting a topic; (2) computerized on‐line library reference search; (3) first draft of paper; (4) paper review by a classmate; and (5) submittal of revised paper. Each step requires a written document and has a class‐discussion component. A side benefit of the discussion component is that it helps to set students at ease about participating in class discussions, which carries over to discussions about the scientific content of the class. The resulting well‐written papers are usually a pleasure to read and grade.

ISSN:0002-9505    

DOI:10.1119/1.18190

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

The Dirac approach to include magnetic charge in Maxwell’s equations places the magnetic charge at the end of a string on which the the fields of the theory develop a singularity. In this paper an alternative formulation of classical electromagnetism with magnetic and electric charge is given by introducing a second pseudo‐four‐vector potential,Cμ, in addition to the usual four‐vector potential,Aμ. This avoids the use of singular, nonlocal variables (i.e., Dirac strings) in electrodynamics with magnetic charge, and it makes the treatment of electric and magnetic charge more symmetric, since both charges are now gauge charges.

ISSN:0002-9505    

DOI:10.1119/1.18191

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP

摘要:

A simple conceptual experiment which seems to violate the general principles of quantum mechanics is reported. The reasoning leading to this contradiction contains a trick which makes the paradox possible. By discussing the failure of the argument the author wishes to draw attention to a fundamental feature of the wave function which is frequently overlooked. Finally, in light of this discussion, a kind of delayed‐choice experiment is described, and an analysis of the related issue of complementarity is made.

ISSN:0002-9505    

DOI:10.1119/1.18192

出版商:American Association of Physics Teachers    

年代:1996

数据来源: AIP