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Apr 2001

Volume 69, Issue 4, pp. 405-525

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Question #78. A question about the Maxwell relations in thermodynamics

Vinay Ambegaokar and N. David Mermin

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 405 | Cited 4 times

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Abstract Unavailable
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01.50.-i Educational aids
05.70.-a Thermodynamics

Question #79. Does plane wave not carry a spin?

R. I. Khrapko

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 405 | Cited 12 times

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Abstract Unavailable
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01.50.-i Educational aids
42.50.-p Quantum optics
42.25.Ja Polarization

Question #80. Relating scalar and pseudoscalar quantities in electromagnetism

J. P. McTavish

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 405

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Abstract Unavailable
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01.50.-i Educational aids
03.50.De Classical electromagnetism, Maxwell equations
41.20.-q Applied classical electromagnetism
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Should I pay attention to the output from physics education R&D?

Donald F. Holcomb

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 407

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Abstract Unavailable
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01.40.G- Curricula and evaluation
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AJP’s Referees, 1988–2001

Kannan Jagannathan, Assistant Editor and Robert H. Romer, Editor

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 409

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When the American Journal of Physics editorial office moved to Amherst in 1988, we began the annual custom of listing the referees who had helped us with referee reports during the preceding calendar year. This year, as the office prepares to move from Amherst College to Kalamazoo College, we print a merged list of the referees who have written referee reports for us between June 1, 1988 and approximately February 15, 2001. It is possible that we have lost the names of a few of our valued referees. If so, we will of course “blame it on the computer,” while at the same time offering our sincere apologies to anyone thus omitted from this lengthy list.   There is no need to say again how important these careful and conscientious reviews are to the quality of the American Journal of Physics. On behalf of all our readers and authors, thank you!
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01.30.-y Physics literature and publications
01.50.-i Educational aids
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Super classical quantum mechanics: The best interpretation of nonrelativistic quantum mechanics

Willis E. Lamb, Jr.

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 413 | Cited 4 times

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It has been shown that Newtonian classical mechanics (NCM) suffers from several kinds of chaotic indeterminacies. That means, a large set of problems treated with NCM gives results which are in wild disagreement with observation. In the present paper, these shortcomings are repaired in a simple, obvious, and essentially unique manner. The NCM theory is thereby transformed into a new theory which is fully equivalent to the Heisenberg, Schrödinger, and Dirac nonrelativistic quantum mechanics, with the vital addition of Born’s probabilistic interpretation of the wave function built in from the start. I call this new theory “super classical quantum mechanics” (SCQM). Using Ehrenfest’s theorem of 1927, the classical limit of the new theory, SCQM, is seen to give exactly the results expected of the repaired Newtonian theory of classical mechanics. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
45.05.+x General theory of classical mechanics of discrete systems
03.65.-w Quantum mechanics
02.50.Cw Probability theory

The elusive chemical potential

Ralph Baierlein

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 423 | Cited 16 times

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This paper offers some qualitative understanding of the chemical potential, a topic that students invariably find difficult. Three “meanings” for the chemical potential are stated and then supported by analytical development. Two substantial applications—depression of the melting point and batteries—illustrate the chemical potential in action. The origin of the term “chemical potential” has its surprises, and a sketch of the history concludes the paper. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
05.70.-a Thermodynamics

The charge distribution on a conductor for non-Coulombic potentials

David J. Griffiths and Daniel Z. Uvanović

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 435 | Cited 1 time

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We study the distribution of charge on a conductor for Yukawa (e−μr/r) and power-law (1/rn) potentials. In the Yukawa case some charge goes to the surface, while the remainder distributes uniformly over the volume. In the power-law case no such general result is available, but we obtain the distribution for spheres, cylinders, and slabs, on the range 1⩽n⩽3. In the Coulomb limit (n=1) the charge all goes to the surface; at the other extreme (n=3) it distributes uniformly over the volume. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems

The van der Waals interaction

Barry R. Holstein

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 441 | Cited 7 times

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The interaction between two neutral but polarizable systems at separation R, usually called the van der Waals force, is discussed from different points of view. The change in character from 1/R6 to 1/R7 due to retardation is explained. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions

Atomic polarization visualized

S. M. Rochester and D. Budker

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 450 | Cited 20 times

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A method of visualizing atomic polarization as a surface in three dimensions is described. The technique is used to illustrate the evolution of polarized atoms in external electric and magnetic fields. This can aid in the understanding of experiments involving the evolution of atomic polarization, such as optical rotation experiments and measurements of discrete symmetry violations in atomic systems. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
32.30.-r Atomic spectra
32.60.+i Zeeman and Stark effects

How to detect buried structures through electrical measurements

Ana Osella, Gabriel Chao, and Federico Sánchez

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 455 | Cited 1 time

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The experiment reported here, performed by advanced undergraduates as a final laboratory work, was intended as an example of the application of the electricity theory to solve problems related to environmental physics. In particular, the aim of the work was to show how we can get the electrical image of the soil and detect the presence of buried structures from simple geoelectrical measurements. First, we developed scale models in the laboratory to recognize the electrical responses of different layered structures and to evaluate the sensitivity of the method and we interpreted the results using one-dimensional inversion codes. Then we proposed a configuration which permitted simulating a buried pipeline and analyzed the electrical response applying a simple two-dimensional numerical code. Finally, we performed field work in order to compare the results with ones obtained through the laboratory scale models. © 2001 American Association of Physics Teachers.
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01.50.Pa Laboratory experiments and apparatus
07.68.+m Photography, photographic instruments; xerography

Electromagnetic interaction momentum and simultaneity

R. Coïsson and G. Guidi

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 462 | Cited 1 time

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Using a simple example of two interacting electric charges, we show that different observers see a different distribution of momentum between the particles and the electromagnetic field, and we discuss how this is related to the relativity of simultaneity (which has to be taken into account even if it seems that we are in a “nonrelativistic” approximation). © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
41.20.-q Applied classical electromagnetism
03.30.+p Special relativity

The Duffing oscillator: A precise electronic analog chaos demonstrator for the undergraduate laboratory

B. K. Jones and G. Trefan

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 464 | Cited 7 times

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A simple electronic circuit is described which can be used in the student laboratory to demonstrate and study nonlinear effects and chaos. The circuit shows the changes to the dynamical properties of the system with respect to three control parameters: the applied voltage amplitude and frequency and the circuit damping. The response voltage and its derivative can be displayed to give the phase space plot and the bifurcation diagram against any control parameter. The circuit is sufficiently ideal and stable to allow comparison of its analog output with the output obtained from standard digital computer simulations. As examples, the routes to chaos with respect to the control parameters and the bifurcation route to chaos, which follows the Feigenbaum scenario, are shown. © 2001 American Association of Physics Teachers.
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01.50.My Demonstration experiments and apparatus
05.45.-a Nonlinear dynamics and chaos
02.30.Oz Bifurcation theory

Fluid-like properties of the probability densities in quantum mechanics

Katsunori Mita

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 470 | Cited 2 times

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The transport properties of the probability fluid are investigated. The transport equation is derived as a generalization of the equation of continuity. This equation is used to examine the properties of the mass flux density, momentum flux density, and kinetic energy flux density of the probability fluid. It is shown that the transport equations of the probability fluid can be represented in a form identical to those of the classical, Eulerian fluid. It is also shown that the transport equations are differential forms of Ehrenfest’s theorem. Local conservation of the mass density and kinetic energy density for the stationary states are examined. Explicit expressions of the mass flux density and kinetic energy flux density are obtained for the 2p state of the hydrogen atom. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
03.65.-w Quantum mechanics
02.50.Cw Probability theory
02.30.Jr Partial differential equations

Regular coordinate systems for Schwarzschild and other spherical spacetimes

Karl Martel and Eric Poisson

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 476 | Cited 37 times

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The continuation of the Schwarzschild metric across the event horizon is a well-understood problem discussed in most textbooks on general relativity. Among the most popular coordinate systems that are regular at the horizon are the Kruskal–Szekeres and Eddington–Finkelstein coordinates. Our first objective in this paper is to popularize another set of coordinates, the Painlevé–Gullstrand coordinates. These were first introduced in the 1920s, and have been periodically rediscovered since; they are especially attractive and pedagogically powerful. Our second objective is to provide generalizations of these coordinates, first within the specific context of Schwarzschild spacetime, and then in the context of more general spherical spacetimes. © 2001 American Association of Physics Teachers.
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01.50.My Demonstration experiments and apparatus
04.20.-q Classical general relativity
04.70.-s Physics of black holes

Reinventing the wheel: Hodographic solutions to the Kepler problems

David Derbes

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 481 | Cited 8 times

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There are two Kepler problems: given the inverse-square law, find the trajectories; or, given Kepler’s laws, find the inverse-square law. Traditionally these problems are solved in the classroom via calculus, but the amount of calculus needed may be prohibitively high for a first-year course. Alternative solutions to the Kepler problems have been discovered, forgotten, and rediscovered for centuries. Many of these employ Hamilton’s hodograph, a graphical representation of an object’s velocity. This article demonstrates hodographic solutions to the Kepler problems, including an algorithm for the construction of parabolic trajectories. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
45.05.+x General theory of classical mechanics of discrete systems
95.10.Ce Celestial mechanics (including n-body problems)
45.50.Pk Celestial mechanics
02.30.Vv Operational calculus

Teaching time-series analysis. I. Finite Fourier analysis of ocean waves

Dennis J. Whitford, Mario E. C. Vieira, and Jennifer K. Waters

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 490 | Cited 3 times

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The introduction of students to methods of time-series analysis is a pedagogical challenge, since the availability of easily manipulated computer software presents an attractive alternative to an understanding of the computations, as well as their assumptions and limitations. A two-part pedagogical tutorial exercise is offered as a hands-on laboratory to complement classroom discussions or as a reference for students involved in independent research projects. The exercises are focused on the analysis of ocean waves, specifically wind-generated surface gravity waves. The exercises are cross-disciplinary in nature and can be extended to any other field dealing with random signal analysis. The first exercise introduces the manual arithmetic steps of a finite Fourier analysis of a wave record, develops a spectrum, and compares these results to the results obtained using a fast Fourier transform (FFT). The second part of the exercise, described in the subsequent article, takes a longer wave record and addresses the theoretical and observed wave probability distributions of wave heights and sea surface elevations. These results are then compared to a FFT, thus linking the two pedagogical laboratory exercise parts for a more complete understanding of both exercises. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
02.30.Lt Sequences, series, and summability
02.30.Nw Fourier analysis
02.50.-r Probability theory, stochastic processes, and statistics
92.10.Hm Ocean waves and oscillations

Teaching time-series analysis. II. Wave height and water surface elevation probability distributions

Dennis J. Whitford, Jennifer K. Waters, and Mario E. C. Vieira

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 497 | Cited 3 times

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This paper describes the second of a two-part series of pedagogical exercises to introduce students to methods of time-series analysis. While these exercises are focused on the analysis of wind generated surface gravity waves, they are cross-disciplinary in nature and can be applied to other fields dealing with random signal analysis. Two computer laboratory exercises are presented which enable students to understand many of the facets of random signal analysis with less difficulty and more understanding than standard classroom instruction alone. The first pedagogical exercise, described in the previous article, uses mathematical software on which the students execute the manual arithmetic operations of a finite Fourier analysis on a complex wave record. The results are then compared to those obtained by a fast Fourier transform. This article, the second of this two-part pedagogical series, addresses analysis of a complex sea using observed and theoretical wave height and water surface elevation probability distributions and wave spectra. These results are compared to a fast Fourier transform analysis, thus providing a link back to the first exercise. © 2001 American Association of Physics Teachers.
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01.50.ht Instructional computer use
02.30.Lt Sequences, series, and summability
02.50.-r Probability theory, stochastic processes, and statistics
47.35.-i Hydrodynamic waves
92.60.hh Acoustic gravity waves, tides, and compressional waves
92.60.Gn Winds and their effects

Path integral and the induction law

F. A. Barone and C. Farina

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 505

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We show how the induction law is correctly used in the path integral computation of the free particle propagator. The way this primary path integral example is treated in most textbooks is a little bit misleading. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
07.68.+m Photography, photographic instruments; xerography

Time-development operator method in quantum mechanics

S. Balasubramanian

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 508 | Cited 7 times

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We discuss the time-development operator method in quantum mechanics. The equivalence of this method and the usual method of expansion in terms of energy eigenfunctions discussed in textbooks is pointed out. As examples of cases of time-dependent Hamiltonians, we discuss the time development of a Gaussian wave packet for a charged particle subject to a time-dependent electric field using an operator differential equation. We also consider a spin in a time-dependent magnetic field through a time-development operator. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
02.10.Yn Matrix theory
03.65.-w Quantum mechanics
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Kronig–Penney model with the tail-cancellation method

Subodha Mishra and S. Satpathy

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 512 | Cited 4 times

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The Kronig–Penney model of an electron moving in a periodic potential is solved by the so-called tail-cancellation method. The problem also serves as a simple illustration of the tail-cancellation method itself. © 2001 American Association of Physics Teachers.
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01.50.-i Educational aids
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Comment on “A simple demonstration of the Alford–Gold effect using a diode laser and optical fibers,” by L. Basano and P. Ottonello [Am. J. Phys. 68 (4), 325–328 (2000)]

A. C. de la Torre

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 513

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Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
42.55.Px Semiconductor lasers; laser diodes
42.81.-i Fiber optics

Comment on “Bound states of a uniform spherical charge distribution—revisited!,” by Brian C. Tiburzi and Barry R. Holstein [Am. J. Phys. 68 (7), 640–648 (2000)]

Frank Rioux

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 514

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Abstract Unavailable
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01.50.-i Educational aids
21.10.Ft Charge distribution
36.10.Dr Positronium

Comment on “Charge density on a thin straight wire, revisited,” by J. D. Jackson [Am. J. Phys. 68 (9), 789–799 (2000)]

O. F. de Alcantara Bonfim and David Griffiths

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 515 | Cited 2 times

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Abstract Unavailable
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01.50.-i Educational aids
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
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Improved eddy current driver-detector for elastic vibrations

Alejandro Morales, Luis Gutiérrez, and Jorge Flores

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 517 | Cited 8 times

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Abstract Unavailable
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01.50.Pa Laboratory experiments and apparatus
46.40.-f Vibrations and mechanical waves
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Cosmology: The Science of the Universe, 2nd ed.

Edward Harrison, Author and Laurence A. Marschall, Reviewer

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 523

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Abstract Unavailable
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01.30.mp Textbooks for undergraduates
98.80.-k Cosmology

Quantum Generations: A History of Physics in the Twentieth Century.

Helge Kragh, Author and Stephen G. Brush, Reviewer

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 524

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Abstract Unavailable
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01.30.Vv Book reviews
01.55.+b General physics
01.65.+g History of science
03.65.-w Quantum mechanics
01.50.-i Educational aids

Magnetic Fields: A Comprehensive Theoretical Treatise for Practical Use

Heinz E. Knoepfel, Author and Daniel C. Mattis, Reviewer

American Journal of Physics -- April 2001 -- Volume 69, Issue 4, pp. 525

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Abstract Unavailable
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01.30.Vv Book reviews
01.50.-i Educational aids
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
07.55.Db Generation of magnetic fields; magnets
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