bluuebunny/crossref_metadata_2025 huggingface dataset:
High-frequency magnetic measurements using small inductive probes
Authors: Beiersdorfer Peter , Clothiaux Eugène J.
Published: March 2005

Experiments with small magnetic probes suitable for advanced undergraduates are described. The experiments are designed to show that an inductive probe does not respond to high-frequency signals (1–70 MHz) as might be expected from experience with probes at low frequencies. Pickup of noninductive signals is demonstrated, resonances are observed, and the inductance, capacitance, resistance, and effective area of the probe are measured. In addition, the conductivity of copper and aluminum is found using thin metal foils.
Applying dimensional analysis
Authors: Remillard Wilfred J.
Published: March 2005

The basic concepts of dimensional analysis have been known for over a half century. However, with the advent of hand calculators and the use of matrices these concepts lend themselves to simple manipulations which can assist a researcher in designing experiments, developing equations, and converting units. Matrix methods are developed and examples are given to illustrate these concepts.
Periodic boundary conditions in special relativity
Authors: Peters P. C.
Published: March 2005

The imposition of periodic boundary conditions on the space-time of special relativity is shown to lead to the existence of a preferred frame of reference. One characteristic of the preferred frame is that it is the frame in which the resulting finite universe has the smallest size. In a frame moving with respect to the preferred frame, global synchronization of clocks cannot be carried out and the transit time to traverse the universe depends on the direction of travel. As measured in a moving frame, a person at rest in the preferred frame can be found at two or more different places at the same time, although the age of the person will be different at each of those places. A ‘‘pole in the universe’’ paradox is presented, the resolution of which requires use of some of these bizarre properties of the universe of periodic boundary conditions.
Measurements on the He–Ne laser lines near 633 nm
Authors: Steinhaus David W.
Published: March 2005

The red line from an inexpensive He–Ne laser is made up of several closely spaced lines. To separate these lines very high spectral resolution is required. This apparatus requirement can be met by a simple modification of a student Fabry–Perot interferometer. Laboratory measurements can then be made to verify the expected number, spacing, and polarization of these lines during a single afternoon laboratory session.
Elementary derivation of the wake pattern of a boat
Authors: Crawford Frank S.
Published: March 2005

An elementary derivation is given for the shape of the wake pattern of a boat traveling at constant velocity in deep water. We find essentially the same results as those found in standard treatments, but our mathematics is easier. All results follow from the fact that the group velocity is half the phase velocity.
Remark on the second law of thermodynamics
Authors: Yeh Hsu-Chieh
Published: March 2005

From Planck’s statement of the second law of thermodynamics it is generally inferred that it is impossible to construct an engine which produces work at the expense only of heat taken from the air or the ocean. The experiment described in this paper demonstrates that when the air and the ocean are combined as a nonhomogeneous reservoir of uniform temperature, it is possible to construct an engine which produces work by extracting heat from the said reservoir. This does not constitute a violation of the second law of thermodynamics, rather that the ‘‘reservoir’’ in the Planck’s statement must be clearly stated as being in equilibrium.
Alive throughout: Wilhelm Busch and physics
Authors: Lotze Barbara , Lotze Dieter P.
Published: March 2005

The works of the most popular German humorist, Wilhelm Busch (1832–1908), a favorite of physicists like Einstein and Born, contain various references to physical science. Selected passages from his books may be used to broaden the scope of physics instruction by incorporating a cultural component. On the other hand, they can serve to expose the humanities student to some basic concepts of physics.
Measurement of e/m using Dunnington’s method—An experiment for advanced undergraduates
Authors: Whyte T. D. , Rymills N. P. J. , Willis J. S.
Published: March 2005

In this article we report an experiment to measure e/m0 using a method based on the work of Dunnington. Electrons are accelerated in an alternating electric field and subsequently deflected in a magnetic field. The measurements which are required are the frequency of the alternating accelerating voltage, the magnitude of the magnetic field at the electron orbit, and the angle through which the electrons are deflected. Using a frequency of 30 MHz the experiment yielded a value for e/m0 of (1.738±0.020)1011 C kg−1.
Note on a common virtual image
Authors: Bartlett Albert A. , Lucero Rodger , Johnson Gordon O.
Published: March 2005

An observer above the plane surface of a liquid of index of refraction n, looking at a point object which is a distance Y below the surface, will see a virtual image of the object. For light rays which emerge in air at an angle of refraction θ2=0, the virtual image will be at a distance (Y/n) below the surface. The case where θ2≠0 is rarely discussed in texts. As a result, students may be left with the impression that the location of the virtual image is independent of θ2. The virtual image is astigmatic and the locations of the different components of the astigmatic image depend on the angle of refraction θ2. The location of the various components of the astigmatic image are derived; a laboratory experiment to measure the locations of the components is described. The results of the measurements are in good agreement with the theory.
Resource Letter SR-1: Synchrotron radiation
Authors: Margaritondo G. , Weaver J. H.
Published: March 2005

This Resource Letter provides a guide to the literature on synchrotron radiation. The letter E after an item indicates elementary level or material of general interest to persons becoming informed in the field. The letter I, for intermediate level, indicates material of somewhat more specialized nature; and the letter A indicates rather specialized or advanced material. An asterisk (*) indicates those articles to be included in an accompanying Reprint Book.
Man-made quantum wells: A new perspective on the finite square-well problem
Authors: Kolbas R. M. , Holonyak N.
Published: March 2005

The observation of man-made quantum size effects is now possible due to advances in semiconductor technology. Interest in quantum-well heterostructures and superlattices has added a new dimension to both the application and perspective of the traditional discussion of a particle in a box. This paper addresses these new perspectives and presents in an elementary manner the techniques employed to model single and multiple square wells in semiconductors. A brief overview of semiconductor microlayer devices is followed by a discussion of the physics of quantum-well heterostructures. Since the behavior of these structures is described by the finite square well, a simple iterative technique to solve for the bound states of single or multiple (coupled) square wells is presented. The iterative technique is quite general and powerful, yet the physical ideas and the mathematics are straightforward and simple. Finally, computer simulation is employed to illustrate the interaction between multiple coupled wells; the results are compared with those obtained via the usual Kronig–Penney model.
An oceanographic Lloyd’s mirror experiment
Authors: LaCasce E. O. , Hays Earl E.
Published: March 2005

An acoustic signal from a cw source towed near the sea surface produces a Lloyd’s mirror type of pattern. The signal received on a six-hydrophone moored array gives a record of this three-dimensional pattern. A comparison of the observed data and calculated pattern using the characteristics of the ocean provides some insight into transmission in a region where the velocity is depth dependent.
Sun and lamps
Authors: Zanetti Vittorio
Published: March 2005

A nonstandard method for determining solar temperature has been presented. This method is based on the comparison between the brightness of a commercially available incandescent lamp and the Sun. This comparison is quantitative, due to the well-known properties of tungsten. Planck’s law too has a fundamental role in this comparison. A silicon cell with an interference filter which has a central wavelength of 600 nm is used to examine the two sources of light. A quite satisfactory value of the solar temperature—about 5700 K—has been obtained in this way, and some interesting points are raised in connection with the radiation constant c2 of Planck’s law. The experiment may be considered as an advanced project concerning solar energy teaching or blackbody radiation theory.
Concerning drops
Authors: Bruce Ian
Published: March 2005

Experimental and computational procedures are outlined for establishing the surface tension of a sessile drop of liquid. Measurements of a drop are made from a microphotograph or by using a novel diverging laser beam projection method. The sessile drop differential equation is found from hydrostatic considerations; this is solved numerically using a Runge–Kutta scheme. A best-fit solution to the experimental curve is found by adjusting two parameters: the drop apex radius of curvature and the surface tension. Reasonable agreement with experiment is obtained.
The pair correlation function: A probe of molecular order
Authors: Bishop Marvin , Bruin C.
Published: March 2005

The general properties of the pair correlation function are reviewed. The computer simulation method of molecular dynamics is used to obtain this function for a variety of conditions for a two-dimensional Lennard–Jones model. It is shown that the pair correlation function is an excellent tool for the investigation of molecular order.
Work and heat transfer in the presence of sliding friction
Authors: Sherwood Bruce Arne , Bernard W. H.
Published: March 2005

The work done by frictional forces has usually been calculated incorrectly. The key to a correct treatment lies in making a careful distinction between a purely mechanical integral of Newton’s second law on the one hand and the first law of thermodynamics on the other. These two equations are the same for point particles but differ for deformable systems, which include systems subject to sliding friction. A model-independent calculation is supplemented by applications to current models for friction. Heat transfer is treated in detail for the case of lubricated friction. Rotational friction is analyzed. An invariant form of the energy equation is presented.
Transient behaviors in the Wien bridge oscillator: A laboratory experiment for the undergraduate student
Authors: Hayashi Yoshikazu , Nakagawa Tomoko
Published: March 2005

Transient behaviors near the oscillation threshold are investigated in a Wien bridge oscillator. Undamped relaxation oscillations familiar in masers and lasers are observed. A burst of oscillations occurs after a delay from switching on a power supply for an operational amplifier used for the oscillator. The shape of the burst closely fits to the hyperbolic-secant function. Observed results are analyzed by van der Pol’s equation and analogies to the phenomena that appear in the magnetic resonance and laser-type oscillators are briefly discussed.
Spreading of a relativistic wave packet
Authors: Almeida Carlos , Jabs Arthur
Published: March 2005

We present a simple general proof that the spreading velocity of a relativistic free wave packet of de Broglie waves is limited. For a wide class of packets we confirm that the limit is the velocity of light, and we show how this limit is approached when the width Δp of the wave packet in momentum space tends to infinity and the minimum width σ(t=0) in ordinary space tends to zero.
The evolution of the speed distribution for a two-dimensional ideal gas: A computer simulation
Authors: Bonomo R. P. , Riggi F.
Published: March 2005

A bidimensional model of an ideal gas has been studied to simulate the evolution of the speed distribution. In the model all the molecules are assumed to be hard disks, the collisions between them are assumed to be elastic, and the distribution of the impact parameters is assumed to be a uniform one. By starting from different initial distributions, it is shown that the system always evolves towards the Maxwell–Boltzmann distribution.
Why spontaneous emission?
Authors: Milonni P. W.
Published: March 2005

This paper is a discussion of that perennial question, ‘‘Why does an excited atom radiate?’’ A satisfactory physical picture emerges when proper account is taken of the interplay between radiation reaction and the (quantum-mechanical) zero-point fluctuations of the radiation field. The fluctuation-dissipation connection between these two effects is therefore emphasized.
Measurement of the terminal velocity in air of a Ping-Pong ball using a time-to-amplitude converter in the millisecond range
Authors: Brandan M. E. , Gutiérrez M. , Labbé R. , Menchaca-Rocha A.
Published: March 2005

An economic time-to-amplitude converter has been designed and built, able to measure time intervals of the order of milliseconds. Its main output is a positive signal proportional to the measured time, appropriate for a multichannel-analyzer input. As an application we have measured the transit time Δt of a vertically falling Ping-Pong ball across a small Δx gap, for different heights of release up to 17 m. The dependence of the speed Δx/Δt on the fallen distance is well described by the model of air resistance proportional to the square of the instantaneous velocity. The measured terminal velocity is 9.5 m/s, 98% of which is attained after falling 12.5 m.
Resource Letter: PWI-1 Plasma waves and instabilities
Authors: Grabbe Crockett L.
Published: March 2005

This Resource Letter provides a guide to the literature on plasma waves and instabilities. Approximately 50% of the references are on linear waves, 25% on nonlinear waves, and 25% on applications. After each reference is a two-letter code. The first letter indicates the level of the material. The letter E after an item indicates elementary level or material of general interest to persons becoming informed in the field; the letter I, for intermediate level, indicates material of a somewhat more specialized nature; and the letter A indicates rather specialized or advanced material. The second letter indicates the type of material, and is either T (tutorial), R (review), B (benchmark), or H (historical). An asterisk (*) in front of an item indicates those articles to be included in an accompanying reprint book. These are primarily benchmark papers. Material from in-print books and review series, as well as most review articles, have been excluded because of page limitations.
On the teaching of the multipole expansion
Authors: Grosse Constantino
Published: March 2005

An expansion based on a finite series of nonideal axial multipoles is presented. It is suggested that it constitutes a better introduction to the teaching of the multipole expansion than the usual power series. As an application, the equivalence between a nonideal dipole and an ideal one plus an infinite set of nonideal octupoles is shown.
Lady or tiger?—The Meitner–Hupfeld effect and Heisenberg’s neutron theory
Authors: Brown Laurie M. , Moyer Donald F.
Published: March 2005

Reports in May 1930 of an anomaly in the scattering and absorption of gamma rays, known as the Meitner–Hupfeld effect, presaged the New Physics of the 1930s. Scattering from light elements agreed with theoretical predictions based upon quantum electrodynamics and the relativistic electron theory of Dirac, but results on heavy targets pointed to a new nuclear absorption effect that was a harbinger of new particles and new phenomena. The experimental investigations of this anomalous absorption placed constraints on theories of nuclear structure, leading Heisenberg, for example, to insist upon the presence of electrons within nuclei as light as helium, even after Chadwick’s discovery of the neutron and Heisenberg’s proposed neutron–proton nuclear model. The anomalous γ-ray behavior was eventually ascribed to electron–positron pair production and annihilation.
The mechanics of flycasting: The flyline
Authors: Spolek Graig A.
Published: March 2005

In order to propel a fishing fly through the air toward the distant quarry, a rather massive line, to which the fly is attached, is cast. As the cast line rolls out, the fly actually accelerates horizontally and seems to defy physical law. The phenomenon is modeled simplistically to determine the magnitude of this effect. In the absence of air drag, the fly can accelerate to increase its velocity by an order of magnitude. Air friction dramatically decreases the effect, but some fly acceleration is still predicted. By tapering the flyline in various ways, the fly velocity history can be significantly modified, and some tapers are predicted to perform better than others.
Recruiting physics teachers on a university campus
Authors: Clark Robert Beck
Published: March 2005

This paper reports on the successful efforts of Texas A&M University in recruiting majors in physics, engineering, and other physical sciences to pursue careers in high school physics teaching.
1986 Richtmyer Lecture: Unification, grand unification, and the unity of physics
Authors: Lederman L.
Published: March 2005

The relationships among the many specialized areas of physics are discussed. The historical aspects are briefly covered, and the relevance of the superconducting super collider is emphasized. (AIP)
Exact solvable model for the Stark effect on a hydrogen atom
Authors: Makarewicz Jan
Published: March 2005

An exact solvable, realistic model for the description of the Stark effect on a hydrogen atom is presented. The model Hamiltonian is used to calculate polarizability of the hydrogen atom by means of variational-perturbation theory.
Magnetic forces and circuits
Authors: Benenson R. E. , Raffaele R.
Published: March 2005

The one-dimensional magnetic stress formula is verified by measuring the force needed to separate pole pieces which are part of a magnetic circuit. Field mapping in the air gap region of the same magnetic circuit is used to estimate the permeability of its ferromagnetic materials.
An experimental test of Newton’s celestial mechanics
Authors: Hardorp Johannes
Published: March 2005

Twelve years of pulsar observations afford the first opportunity to see the Sun’s motion around the barycenter of the solar system. Exercises exploring the orbit of the earth around the Sun are being recommended for use in junior physics courses.
Representation of relativistic quantities by trigonometric functions
Authors: Majerník V.
Published: March 2005

A ‘‘space-time angle’’ φ is defined by setting v=c(sin φ). This leads to a form of Lorentz transformations which uses simple real trigonometric functions and yields a graphic correlation of important relativistic quantities for particles and for corresponding de Broglie waves. A number of relativistic relationships is obtained by the use of common trigonometric identities and formulas.
Cooling by immersion in liquid nitrogen
Authors: Listerman Thomas W. , Boshinski Thomas A. , Knese Lynn F.
Published: March 2005

When an object is cooled by immersion in a liquid, there is an unexpected increase in the violence of boiling just before the boiling stops. Most people seem fascinated by this phenomenon yet few are acquainted with its explanation in terms of a change in the heat-transfer mechanism from film boiling to nucleate boiling. We have developed two variations of an intermediate level undergraduate laboratory experiment to measure the heat-transfer rate after a sample is immersed in liquid nitrogen. The temperature of the sample, as measured by a thermocouple, is recorded as a function of time using either a potentiometer strip-chart recorder or a digital voltmeter–microcomputer combination. The heat-transfer rate as a function of sample temperature is computed from these results, and the reason for the effect is clearly seen.
Nonconservation of amplitude in wave division—a compelling example
Authors: Kay L.
Published: March 2005

If the plates of a Fabry–Perot etalon have high reflectivity, then the first plate acting alone will reflect almost all the intensity of a wave incident on the etalon. Nevertheless, the intensity transmitted by the etalon may be almost equal to the incident intensity. The resolution of this apparent paradox constitutes a cogent illustration of the consequences of nonconservation of amplitude in wave division by partially transmitting surfaces.
A combined form of the laws of Ampere and Biot–Savart
Authors: Garretson Craig M.
Published: March 2005

This article gives a combined form of the laws of Ampere and Biot–Savart which allows us to calculate the infinitesimal magnetic circulation around a closed loop ∑δB⋅δl in terms of the current flow i through an infinitesimal current path δs, and the change in the solid angle subtending the closed loop δΩ as the apex of the solid angle traverses δs:∑δB⋅δl=iδΩ×10−7. After giving its derivation from the law of Biot–Savart, the combined form is applied to a variety of magnetostatic problems. The illustrative examples, none of which requires the use of calculus for its solution, include the usual introductory course examples such as determining the magnetic field inside a toroidal coil, and at the center and along the axis of a circular current loop. In addition, the potentialities of the combined law are demonstrated by determining the field anywhere in the plane and along the axis of a rectangular current loop. Appendices include discussions of solid angles and relativistic effects.
The quantum point-mass pendulum
Authors: Cook G. P. , Zaidins Clyde S.
Published: March 2005

The question of how long it takes an inverted point-mass pendulum to fall according to classical, semiclassical, and quantum theories is examined. The semiclassical analysis is based on the uncertainty introduced by measurement.
Correlation of quantum properties and the generalized Heisenberg inequality
Authors: Lévy-Leblond Jean-Marc
Published: March 2005

Attention is drawn to the significance and interest of the covariance and correlation coefficient for two physical properties of a quantum system. The generalized Heisenberg inequality between two such properties, in terms of their commutator and anticommutator, is interpreted as setting an upper bound, of quantum nature, on their correlation coefficient.
Integrable motion of a swinging Atwood’s machine
Authors: Tufillaro Nick
Published: March 2005

The motion of a swinging Atwood’s machine is shown to be integrable when the mass ratio is three. Hamilton–Jacobi theory is used to explicitly exhibit the first integral.
Resolution of a cosmological paradox using concepts from general relativity theory
Authors: Silverman Abraham N.
Published: March 2005

According to the big bang theory, the universe began about 15 billion years ago and has been continually expanding ever since. If certain elementary physical concepts are naively applied to this cosmological theory, it can lead to a paradox in which distant astronomical objects seem to have lain at distances from the Earth larger than the possible size of the universe. The paradox is resolved by using concepts from general relativity theory. These concepts may appear startling to some readers.
Risk analysis of buried wastes from electricity generation
Authors: Cohen Bernard L.
Published: March 2005

There has been a great deal of public concern about the dangers of buried radioactive waste from the nuclear industry. The rational approach to evaluating these concerns is to develop quantitative estimates of the health impacts to be expected from these wastes, and compare them with the health impacts of wastes from alternative technologies. It is our purpose here to outline that process and develop the results.
Untenability of simple ensemble interpretations of quantum measurement probabilities
Authors: Gillespie Daniel T.
Published: March 2005

Some interpretations of quantum mechanics try to describe the probabilistic nature of quantum measurements in a way that allows a system in a pure state to always have precise (if not simultaneously knowable) values for all its observable variables. In what might be called a simple ensemble interpretation, the quantum mechanical state vector is assumed to define a statistical ensemble of identically prepared systems, each of which has precise values for all its observable variables, and the act of measurement is equivalenced to a straightforward sampling of that ensemble. It is shown here, in a manner that should be suitable for a first course in quantum mechanics, that a simple ensemble interpretation is not possible for some quantum systems, and hence is untenable as a general premise. The analysis is essentially a repackaging of the Bell argument against hidden variables, although hidden variables are never invoked here.
Using videotapes to study damped harmonic motion and to measure terminal speeds: A laboratory project
Authors: Greenwood Margaret Stautberg , Fazio Frances , Russotto Marie , Wilkosz Aaron
Published: March 2005

A sphere, attached to the end of a spring, is immersed in glycerin. The motion of the sphere was videotaped as it traveled toward the equilibrium position and we compared the position-versus-time measurements from each frame of the videotape with theoretical calculations to extract the viscosity. Dropping the sphere in glycerin and using videotapes to find the terminal speed also yields the viscosity of glycerin.
Undergraduate experiment: Determination of the band gap in germanium and silicon
Authors: Kirkup L. , Placido F.
Published: March 2005

A method for determining the band gap in germanium and silicon at 0 K based upon the temperature dependence of the electrical conductivity of a p-n junction is described. Results are given for the band gaps that are in good agreement with the accepted values.
Derivation of the potential energy for the inverse square force—Without calculus
Authors: Mallow Jeffry V.
Published: March 2005

A derivation is presented for the potential energy using the assumption of elliptical orbits for a mass under the influence of a 1/r2 force. This eliminates the need for a calculus-based derivation, and is therefore, appropriate for a wide range of nonmajors’ introductory physics courses.
An elementary method for introducing the concept of reciprocal lattice
Authors: Chen Nan-Xian
Published: March 2005

The concept and properties of the reciprocal lattice are naturally and simply deduced from a definition of the indices of lattice planes without any other a priori assumption. The relationship between this definition and conventional Miller indices is demonstrated directly.
Water waves in a ripple tank
Authors: Kuwabara Goro , Hasegawa Toshihiro , Kono Kimitoshi
Published: March 2005

The profiles of water waves in a ripple tank were studied for various water depths. Wave forms with moderately large amplitudes varied with propagation at the depths of 0.5 and 1.0 cm due mainly to the nonlinear effects. The front faces of crests became steep, deviating appreciably from a sinusoidal form, and at 0.5-cm depth new ripples were excited in front of the steep forward face. At depths above 2 cm the waves continued to move with almost permanent sinusoidal forms. Ripple tank experiments are appropriate as laboratory work for an undergraduate course as well as for a demonstration of the nature of waves in an elementary physics course.
Electrostatic problems in nonlinear media
Authors: Brito Pedro , Grosse Constantino , Halloy Christian
Published: March 2005

A straightforward method is presented which permits us to solve electrostatic problems in nonlinear media. It is used to obtain the potentials for the configurations usually encountered in classical books on electromagnetism, but only solved in the linear case. These are nonlinear sphere in a linear medium with applied field, linear sphere with a dipole in its center in a nonlinear medium, and linear sphere in a nonlinear medium with applied field. In all cases, plots of the equipotentials are given.
Compensated Cavendish balance
Authors: Karim Munawar , Toohey William J.
Published: March 2005

Electrical and mechanical modifications are introduced in a Leybold version of the Cavendish balance. An electromagnetic servosystem is described where eddy currents generate a torque to compensate the gravitational torque. Electronic damping reduces the settling time to a few minutes. The apparatus is portable and is immune to the Earth’s magnetic field.
Carl Neumann versus Rudolf Clausius on the propagation of electrodynamic potentials
Authors: Archibald Thomas
Published: March 2005

In the late 1860’s, German electromagnetic theorists employing W. Weber’s velocity-dependent force law were forced to confront the issue of energy conservation. One attempt to formulate a conservation law for such forces was due to Carl Neumann, who introduced a model employing retarded potentials in 1868. Rudolf Clausius quickly pointed out certain problems with the physical interpretation of Neumann’s mathematical formalism. The debate between the two men continued until the 1880’s and illustrates the strictures facing mathematical approaches to physical problems during this prerelativistic, pre-Maxwellian period.
Learning from computers about physics teaching
Authors: Taylor Edwin F.
Published: March 2005

Experience with teaching uses of computers and an analogy between education and nutrition help in reexamining the ways physics is taught, both old and new. The levels of 16 ‘‘educational nutrients’’ for four conventional teaching modes (textbooks, lectures, homework/exams, and standard laboratory) and five uses of computers in education (Tutorial, Demonstration/Simulation, Modeling Toolkit, Laboratory Aid, and Student as Programmer) are estimated. This analysis is used to predict some future developments in college physics teaching.
Determination of Fermi momentum using Compton scattering: An undergraduate experiment
Authors: Manninen S. , Hämäläinen K. , Paakkari T.
Published: March 2005

A method to determine Fermi momentum in simple metals using Compton scattering of low-energy photons from a gamma ray source is described. Measurements can be done in room temperature and no special sample quality requirements are needed. The interpretation of the experiment shows also the close relation of the electronic quantities in position and momentum space.
Displacement measurement by sandwich speckle photography
Authors: Bahuguna R. D. , Lee Sean
Published: March 2005

A simple modification of ordinary double-exposure speckle photography is described. The two exposures are made on two different holographic plates. After processing, the two plates are sandwiched together and illuminated by a direct laser beam. The resulting Young’s fringes can be manipulated by tilting the sandwich specklegram to yield the amount and sign of the displacement of the object.
The normal mode structure on the two-dimensional flame table
Authors: Daw Harold A.
Published: March 2005

The flame structure on a two-dimensional flame table is analyzed in terms of the eigenfunctions of the applicable geometry. The mathematical solutions to the pictures reproduced in an earlier article [H. A. Daw, Am. J. Phys. 55, 733 (1987)] are given. In particular, the flames are found to be strongest at the zeros of the eigenfunctions for the pressure amplitude and therefore follow ‘‘normal operation’’ [G. Ficken and F. C. Stephenson, Phys. Teach. 17, 306 (1979)]. ‘‘Reversal’’ is also clearly observed on the flame table.
Potential energy of interaction for two magnetic pucks
Authors: Shelton D. P. , Kettner M. E.
Published: March 2005

An air table experiment is described in which the interaction force and potential energy for a pair of magnetic pucks are measured as functions of the separation of the pucks. The relation between the force and potential energy is demonstrated by graphical integration. The experiment is also well suited to an air track.
An introductory low-cost magnetic field experiment
Authors: Golden Lawrence B. , Klein James R. , Tongson Luisito
Published: March 2005

This article describes a magnetic field experiment based on the use of Hall effect transducers to measure the axial magnetic field of a real solenoid. The low cost of fabricating the hardware and the need for only an oscilloscope and a low-voltage power supply to make the required measurements allow the smallest physics department to adopt such an experiment.
Low-voltage models of particle accelerator circuits
Authors: Gilgenbach R. M.
Published: March 2005

Low-voltage accelerator models are described that can be used either for classroom demonstrations or for laboratory courses. Two types of circuit models are presented: (1) the Marx generator and (2) the Cockroft–Walton (ladder circuit). These low-voltage circuit models exhibit the basic characteristics of their high-voltage counterparts.
Rocking oscillatory motion and a technique for its measurement
Authors: Klingsporn Paul E.
Published: March 2005

Equations are derived giving the period of rocking oscillatory motion of various bodies when placed on a flat horizontal surface, displaced from equilibrium, and released. The bodies include a sphere and a circular disk with a flat surface, a circular disk with a circular hole, and elliptical disks with circular and elliptical holes. A technique that can be used in an undergraduate mechanics laboratory is described for determining the period of rocking oscillatory motion. The technique consists of measuring the frequency with which electrical continuity is completed when a metallic body instantaneously makes contact with two conducting plates as it undergoes rocking oscillatory motion. The timing is accomplished with digital electronics.
Air track with a distributed infrared detector system
Authors: Gould Laurence I. , Workman Harry
Published: March 2005

A novel air track system is described which contains many permanently mounted emitter–detector pairs. This enables a computer to make quickly a large number of accurate position and time measurements for each run. Because the emitter–detectors employ infrared light, the system is essentially insensitive to normal ambient radiation. (In addition, the system design is simple enough for a student project.) Details of the apparatus will be sketched and a variety of experiments will be discussed.
Walsh functions and the solution of nonlinear differential equations
Authors: Ahner Henry F.
Published: March 2005

The way that Walsh function expansions may be used to solve sets of nonlinear equations with one independent variable is reviewed and extended. The new approach is shown to be equivalent to intrinsic recursive difference equations. The magnitude of errors, which are proportional to the cube of the step size, may be easily estimated at each step. The new approximation is compared to Cromer’s Last Point Approximation. Examples include the solution of the linear harmonic oscillator, which provides the trigonometric expansion of Walsh functions, the solution of the nonlinear damped oscillator with a time-dependent driving function (Duffing’s equation), and an example of a stick-slip model from earth science.
Lagrangian formulation of a transmission line
Authors: Morgan Michael J.
Published: March 2005

A Lagrangian formulation is given for a transmission line, wherein the ‘‘equation of motion’’ for wave propagation on a lossy line (i.e., the telegrapher’s equation) is generated by an appropriate (mathematical) Lagrangian density. However, a more careful examination reveals that this Lagrangian density can also be interpreted as representing the continuum limit of a chain of lossless bandpass filter sections with variable inductance and capacitance. To provide a consistent description of the lossy line, a variational principle, based upon a modification of Hamilton’s principle, is exploited. The resulting Euler–Lagrange equation involves a (physical) Lagrangian density weighted with a time-dependent dissipation factor that explictly describes a nonisolated system losing energy to its surroundings.
Reply to ‘‘Comment on ‘Bell’s theorem and the foundations of quantum physics’ ’’ [Am. J. Phys. 5
6, 567 (1988)]
Authors: Stapp Henry P.
Published: March 2005

EPR locality is discussed from the point of view of determinism. (AIP)
A Newtonian cosmology Newton would understand
Authors: Lemons Don S.
Published: March 2005

Isaac Newton envisioned a static, infinite, and initially uniform, zero field universe that was gravitationally unstable to local condensations of matter. By postulating the existence of such a universe and using it as a boundary condition on Newtonian gravity, a new field equation for gravity is derived, which differs from the classical one by a time-dependent cosmological term proportional to the average mass density of the universe. The new field equation not only makes Jeans’ analysis of the gravitational instability of a Newtonian universe consistent, but also gives rise to a family of Newtonian evolutionary cosmologies parametrized by a time-invariant expansion velocity. This Newtonian cosmology contrasts with both 19th-century ones and with post general relativity Newtonian cosmology.
Another look at the quantum mechanical entropy of mixing
Authors: Dieks Dennis , van Dijk Vincent
Published: March 2005

It is often stated that the Gibbs ‘‘paradox’’ is resolved or at least alleviated in quantum mechanics because the value of the quantum mechanical entropy of mixing continuously approaches zero if the difference between the particles that are being mixed is made to vanish (i.e., if the value of the inproduct of the respective quantum states goes to one). In this article, the justification of that claim is discussed. It is pointed out that, strictly speaking, an entropy of mixing is not defined if the quantum states of the particles are no longer orthogonal. It seems, therefore, that from a fundamental point of view the Gibbs ‘‘paradox’’ is there no less in quantum mechanics than in classical statistical mechanics.
Analytic approximation for the chemical potential of an ideal boson system
Authors: Aguilera-Navarro V. C. , Estévez G. A.
Published: March 2005

The expansion in Dirichlet series for the Bose–Einstein integral function is reverted to find the fugacity of the system. The ensuing result and the Padé approximant technique are judiciously blended for determining a simple and accurate expression for the reduced chemical potential of a boson system, valid for arbitrary values of the Bose–Einstein integral.
Comparison of the Ampère and Biot–Savart magnetostatic force laws in their line-current-element forms
Authors: Christodoulides C.
Published: March 2005

The force laws of Ampère and Biot–Savart in magnetostatics are compared using the geometrical model of a closed curve to represent a current loop. The two laws give identical results when forces between separate current loops are considered and also for the force exerted by a current loop on a rectilinear part of itself. According to both laws, these self-forces diverge wherever the curvature of the curve representing the current loop is not equal to zero. Differences in the predictions of the two laws are shown to appear only as differences in diverging forces when evaluating forces of a current loop on a part of itself and to be entirely due to the oversimplified and unrealistic geometrical model used for the current loop.
Scattering from an attractive delta-function potential
Authors: Van Siclen Clinton DeW.
Published: March 2005

A one−dimensional calculation is carried out to determine the phase shifts for scattering from an attractive delta−function potential. (AIP)
Lambda versus first-order transitions
Authors: Bailyn M.
Published: March 2005

If the lambda transition of, say, helium is regarded as taking place over a temperature region, then an integrated latent heat and latent volume that satisfy a Clausius–Clapeyron equation can be defined. The situation is analogous to what happens in ordinary first-order transitions, which suggests a generalization of the Ehrenfest classification scheme for transitions.
Quantum unbinding in potentials with 1/r P tails
Authors: Zia R. K. P. , Lipowsky R. , Kroll D. M.
Published: March 2005

Potentials with repulsive power behavior at large distances may or may not have a zero-energy bound state, depending only on the power p and, if p=2, the strength. For the case of no zero-energy bound state, we further study how the state unbinds as the attractive, small r part of the potential is tuned to let the binding energy go to zero. Although motivated by the physics of wetting, this problem is well suited for senior or graduate level quantum mechanics courses by giving a novel perspective of solutions to one-dimensional Schroedinger equations.
Does a group velocity larger than c violate relativity?
Authors: Peters P. C.
Published: March 2005

It is often assumed that relativity restricts the group velocity to be less than the speed of light. In this article, this assumption is examined in the context of electromagnetic waves propagating through a dilute plasma. The index of refraction is found from the phase shift in a thin slab of plasma. The response of the same slab to a incident δ-function pulse is also found. After passing through the slab, the pulse acquires a constant tail, in the limit of a thin slab, and the response to an oscillatory wave is recovered by superposition. By considering a material in which the tail has the opposite sign, it is shown that the group velocity can be larger than c without having any signal propagate faster than c.
Equilibrium configurations of parallel repulsive permanent magnets placed inside a circle
Authors: Pescetti D. , Piano E.
Published: March 2005

The equilibrium configurations of a plane system of N equal, parallel, repulsive, permanent magnets constrained inside a circle of radius R are considered. Simple demonstration experiments with permanent magnets gliding on an air table are described. One finds that the magnets can gather in various stable patterns, either symmetrical or nonsymmetrical, the actual configuration being a function of the system’s history. The theoretical analysis has been restricted to a comparison between the energies of the following configurations: (A) All N magnets uniformly distributed around the circumference of radius R; (B) N−1 magnets uniformly distributed around the circumference of radius R plus one magnet at the center. It is shown that the energy of configuration A is lower than that of configuration B only for N smaller than a critical value Nc.
Electromagnetic quantities and units derived from classical relativistic electrodynamics
Authors: Mana Giovanni
Published: March 2005

The present article deals with a procedure for establishing the systems of electromagnetic quantities and units in the framework of the covariant formulation of electrodynamics. The dimensions and units of electromagnetic quantities are obtained from the action for the field and the charged particles interacting with it. Relations are thus established between the quantities used in the covariant formulation of electrodynamics and those used in the nonrelativistic approximation when SI units are employed. It is pointed out that quantities ε0 and μ0 appear explicitly in Maxwell equations written in SI units only to ensure the coherence of this system of units, but that they have no meaning as universal physical constants.
The image of the physicist in modern drama
Authors: Brouwer W.
Published: March 2005

While the role of the scientist in society has been a subject for playwrights from the time of the Renaissance onwards, quite a number of post-World War II plays have focused on the role physics and physicists play in modern society. In this article, the plays of Bertold Brecht, Friedrich Dürrenmatt, William Golding, and Heinar Kipphardt are reviewed, which focus especially on the difficult choices faced by physicists in the modern world in which the consequences of physics-based technology are immense, if not overwhelming. These plays also provide an attractive context for discussion on science and social responsibility.
Resource Letter FR-1: Fractals
Authors: Hurd Alan J.
Published: March 2005

This Resource Letter provides a guide to the literature on fractals. Although ‘‘fractal’’ is a relatively new term in science, unifying many new ideas with established ones, its wide application and general popularity have made it one of the fastest growing fields in statistical physics. The letter E after an item indicates elementary level or material of general interest to persons becoming informed in the field; the letter I, for intermediate level, indicates material of somewhat more specialized nature; and the letter A indicates rather specialized or advanced material. An asterisk (*) indicates those articles to be included in an accompanying Reprint Book.
Relativity and electromagnetism: The force on a magnetic monopole
Authors: Rindler Wolfgang
Published: March 2005

On the occasion of the 100th anniversary of the first publication, by Oliver Heaviside, of what is now known as the Lorentz force law in electromagnetic theory, the analogous force law for magnetic monopoles is examined. Its relevance and limitations in calculating the force and torque on small current loops are discussed, and both its heuristic and practical uses are demonstrated.
Wobbling, toppling, and forces of contact
Authors: McGeer Tad , Palmer Leigh Hunt
Published: March 2005

Analyses and experiments are described for two familiar systems that upon close inspection reveal some surprises. The wobbling domino provides a simple model for some important features in the mechanics of walking. It also makes a sensitive level. The toppling pencil calls for careful treatment of friction.
New graphical methods for linear regression with errors: Unweighted data
Authors: Lichten William
Published: March 2005

This article shows that the usual intuitive method for estimating the error in the slope of a graphical, straight-line fit to a set of data points errs by a factor ∼(N)1/2. For the first time, this article derives from the usual analytical formulas graphical estimates for the errors in the intercept a and slope b for the equation y=a+bx. The result is extended to estimating the error in any derived value y′=a+bx′.
Statistical treatment of effusion of a dilute gas
Authors: Bernardini Carlo
Published: March 2005

The problem of effusion of a low-pressure gas consisting of N molecules through a hole is considered by using simple probability concepts such as Poisson distribution and composition of probabilities. A well-known partial differential equation, accurate up to the order 1/N, the Fokker–Planck equation, is found and solved by standard techniques. Numerical examples are given concerning characteristic times and the rate of leakage.
Nonfrictional hysteresis in a rotating U-tube
Authors: Denardo Bruce , Barber Brad , Folley Chris , Wright William
Published: March 2005

The equilibrium states of a liquid in a rotating U-tube are investigated theoretically for the case where the axis of rotation lies between a vertical arm and the axis of symmetry. Due to the combination of the gravitational, centrifugal, and constraint forces on the liquid, the position can be hysteretic as the angular velocity is varied. Associated with the hysteresis is an instability in which the liquid jumps to a different type of equilibrium state. The behavior is explained qualitatively and derived quantitatively for a square U-tube. The essential results are generalized to tubes with rounded corners. Finally, there is a brief comment on an experiment in which the hysteresis has been observed.
Meissner oscillator
Authors: Ouseph P. J.
Published: March 2005

An apparatus consisting of two Y(1)Ba(2)Cu(3)O(7) superconducting disks and two disk magnets is used to demonstrate Meissner Effect. (AIP)