bluuebunny/crossref_metadata_2025 huggingface dataset:
Personalized introductory courses: A longitudinal study
Authors: Hedges Larry
Published: March 2005

Groups of 139 and 137 undergraduate students took three physics courses taught by either the personalized system of instruction or the lecture-discussion method. Students from these groups were compared in two subsequent chemistry courses and a subsequent biology course. The PSI group achieved significantly higher grades in each case. The junior year major area grades of students who majored in applied mechanics and engineering sciences, biology, chemistry, and physics were also compared. In each case, the PSI group achieved significantly higher grades. For each comparison, the mean high school grade point average, SAT scores, and freshman university grade point average were used to verify that no selective attrition had occurred.
The uniformly accelerated reference frame
Authors: Hamilton J. Dwayne
Published: March 2005

The observations that would be made by a uniformly accelerated observer are considered in detail. These include the observer’s event horizon, the variation of clock rates with position (which implies that the gravitational red shift is not totally dependent on curvature), and the effects to be expected when the motion of a freely falling object is followed. Consideration of the similarities between this reference frame and a real gravitational field is also given. A geometrical method for the construction of the reference frame of the accelerated observer is described in an Appendix.
The formation and optimization of interferometric fringes
Authors: Pernick Benjamin J. , Leib Kenneth G.
Published: March 2005

Expressions to describe fringe contours in the region of interference of two coherent beams are derived for three combinations of plane and spherical wave geometries. Equations for the fringe contours for these basic configurations are given in detail. The fringe contrast ratio is shown to be spatially variable whenever spherical wave fronts are involved and can be controlled by altering the reference- to signal-beam irradiance ratio. These results are important for the fabrication of matched filters, holographic components, and optical interferometric testing.
Electric energy density in a dissipative medium by circuit analog
Authors: Fung P. C. W. , Young K.
Published: March 2005

In a dispersive and dissipative medium, the electric energy density is no longer given by (1/2)E⋅D. When the dielectric function is given, the electric energy density of a monochromatic wave can be calculated by considering the energy stored in an equivalent linear circuit.
Why does the sun shine?
Authors: Nauenberg Michael , Weisskopf Victor F.
Published: March 2005

In order to understand the fundamental properties of a star in radiative equilibrium, a simplified model is introduced which yields relations for physical quantities by elementary methods. In particular, the dependence of these quantities on the parameters of the star and on the fundamental constants of nature is exhibited. Numerical evaluation of these relations is in good agreement with observation and with more elaborate calculations.
A new course: The physical principles of biological instrumentation
Authors: Newrock Richard S.
Published: March 2005

We present the outline of a new course designed to teach the physical principles underlying biological measurements. This course, intended for undergraduate and first-year graduate students who have taken noncalculus introductory physics, is primarily aimed at biological science and biophysics majors interested in research careers in those fields. The course consists of lectures and demonstrations on a series of topics including NMR, ultracentrifugation, electronics, and optical and electron microscopy. Our intent is to teach the student the principles underlying the measurements they perform in their laboratories and the uses and limitations of the various techniques.
UMR, Incorporated: A scenario for roleplaying in an advanced undergraduate physics laboratory
Authors: Sparlin Don M. , Reinisch Louis
Published: March 2005

This paper describes a scenario for an upper-level undergraduate laboratory in which the students take roles as staff members in a contract research company, UMR, Inc. Each student is assigned to a role as Senior Scientist, Researcher, or Technician based on their letter of application, resume, and personal interview. Students are assigned to research groups and participate in a project feasibility study and in writing the resulting proposal. The assembly of apparatus, data taking, and data analysis proceed as in the usual project laboratory. At the end of the semester each student writes a section of the final report and presents a 10-min technical talk. The instructor and the assisting graduate student assume the roles of President/Chief Consultant and Vice President/Associate Consultant/Stockroom Man, respectively.
Anharmonic vibrations of an ’’ideal’’ Hooke’s law oscillator
Authors: Thomchick John , McKelvey J. P.
Published: March 2005

The vibrations of a mass connected to fixed supports by two ’’ideal’’ Hooke’s law springs are considered. Although the longitudinal vibrations of this system are always harmonic, the transverse vibrations are, in general, anharmonic even though both springs obey Hooke’s law. In fact, it is found that as the supports are brought together, allowing the springs to become slack, the purely transverse motion becomes strongly anharmonic even for small displacements of the mass from its equilibrium position. This independent oscillator model seems to possess many of the properties of an ion in a crystal undergoing a soft mode activated transition. We suggest that the model may serve as a useful conceptual starting point in the study of these transitions. Some particular solutions of the dynamical equations for the model system are investigated in detail.
Holographic interferometry for pure rotation
Authors: Tagliaferro William E. , Lee P. L.
Published: March 2005

An experimental arrangement which can be used for double exposure holographic interferometry is described. We have used this setup to measure a series of rotations which range from 4×10−5 to 5×10−4 rad. The result is in excellent agreement with theory.
Philosophy of physics in general physics courses
Authors: Marquit Erwin
Published: March 2005

General physics textbooks usually introduce fundamental concepts on the basis of controversial philosophical outlooks—usually one or another form of philosophical empiricism—without indicating this either to the student or the instructor. The philosophical approaches in a number of currently used textbooks are examined critically from a dialectical materialist viewpoint.
Why is g larger at the poles?
Authors: Iona Mario
Published: March 2005

It is frequently stated that the value of the acceleration due to gravity at the pole is larger than at the equator because the poles are closer to the center of the earth due to the earth’s oblateness. This statement seems misleading in that it attributes significance to the center of mass in such considerations and seems to imply that there is a simple distance dependence. It will be shown that the increase of g due to flattening of a uniform sphere would be only 1/10 as large as would be expected from a 1/r2 relation, and is only about 1/3 of the observed value. The measured value is larger because the earth’s density is not uniform but increases toward the center.
Tuning the ill-tempered clavier
Authors: Bernstein Alan D.
Published: March 2005

The equally tempered scale is modified in piano tuning as a result of the inharmonicity of the partials produced by strings of non-negligible stiffness: An empirical method is described by which tuning may be accomplished satisfactorily by matching measured fundamental frequencies to values determined using a pocket calculator.
Computers as an aid to increasing physical intuition
Authors: Bork Alfred
Published: March 2005

An important aspect of education in the sciences is the development of intuition concerning phenomena predicted by fundamental theories. Science education today is primarily aimed at expounding theories and showing how to apply them. The computer can greatly aid students in building such intuition by providing a rich range of experiences not found in the everyday world or in the laboratory. Examples are given from the work of the Physics Computer Development Project at the University of California, Irvine.
The scattering of particles with spin from targets with spin
Authors: Stewart Noel M.
Published: March 2005

The density matrix is used to obtain an expression for the mean value of any spin operator in the scattering of particles with arbitrary spin. The example of spin-1/2–spin-1 scattering is developed and physical information obtained by establishing connections with the polarization tensor and Wolfenstein observables.
Determination of molecular size and Avogadro’s number: A student experiment
Authors: Alexandrakis George C.
Published: March 2005

In this paper we describe a simple and inexpensive student experiment for the estimation of molecular size and Avogadro’s number. The results are close to the accepted values. We use elementary kinetic theory and two pieces of experimental information. The diffusion length of iodine in air at 100 °C as a function of time is one piece of data used; the other is the change in volume of a given small quantity of carbon dioxide as it goes from the solid to the gaseous state. This experiment is an adaptation of Rogers’ demonstration experiment. For demonstration purposes one uses bromine diffusion in air at room temperature and the volume change upon evaporation of a small quantity of liquid nitrogen.
Integrated circuit stellar magnitude simulator
Authors: Blackburn James A.
Published: March 2005

An electronic circuit is described which can be used to demonstrate the stellar magnitude scale. Six rectangular light-emitting diodes with independently adjustable duty cycles represent stars of magnitudes 1 through 6. The logarithmic response of the eye is experimentally verified.
Lattice vibrations in a linear triatomic chain
Authors: Kesavasamy K. , Krishnamurthy N.
Published: March 2005

The analysis of lattice vibrations of a diatomic chain is extended to a one-dimensional triatomic chain. Dispersion relations have been worked out. Some special cases, such as the vibrations of a monoatomic chain and the vibrations of linear AB2-type ionic and molecular lattices, are discussed using the general results of the triatomic chain. The displacements of atoms in the normal modes and the general solution of the problem have been outlined.
Experiments on magnetic materials
Authors: Schneider C. S. , Ertel John P.
Published: March 2005

The construction and use of a simple apparatus to measure the magnetization density and magnetic susceptibility of ferromagnetic, paramagnetic, and the diamagnetic solids and liquids are described. The apparatus is valuable in demonstrations, student laboratories, and undergraduate research.
The Leidenfrost phenomenon
Authors: Curzon F. L.
Published: March 2005

The paper describes four demonstrations, suitable for a large lecture hall, of the Leidenfrost phenomenon. The demonstrations show the floating of liquid drops on their own vapor above a hot surface, the delayed quenching of red-hot brass by water, the explosion of vessels containing suspended liquid droplets, and the momentary incombustibility of living tissue immersed in boiling oil. The paper also contains some history of the study of phenomenon, and suggests that it should, in fairness to Boerhaave’s prior description, be renamed the Boerhaave-Leidenfrost phenomenon.
Summary and recommendations of the Southeast Asian Regional Conference on University Physics Education
Authors: Singh Chatar , Seward R. J.
Published: March 2005

This paper is primarily a presentation of the recommendations developed by a conference (RCUPE) held in May, 1977 for the express purpose of discussing the special problems of teaching physics in the Southeast Asian region. The Conference was attended by almost 100 participants representing 11 countries of the region. The principal theme that emerged from the Conference was the importance of developing economic and cultural self-reliance in the region, and many of the recommendations concerned ways of achieving such self-reliance in the field of university physics education.
Complete vector spherical harmonic expansion for Maxwell’s equations
Authors: Lambert R. H.
Published: March 2005

Conventional expansions of solutions to Maxwell’s equations in vector spherical harmonics apply only outside the sources. The complete solution, applying both inside and outside the sources, is given here. Harmonic time dependence is assumed.
Simple derivation of the magnetic field inside a long rod of magnetized material
Authors: Dahm A. J.
Published: March 2005

A simple application of Ampere’s law yields the magnetic field inside a long rod of magnetized material. This derivation avoids more difficult mathematical techniques and some of the limitations of other simple approaches.
Verification of Compton collision and Klein-Nishina formulas−an undergraduate laboratory experiment
Authors: Singhal R. P. , Burns A. J.
Published: March 2005

An experiment, which verifies the Compton collision formula and the angular dependence of the Klein-Nishina formula, is described. The angular range studied is from 30° to 120°. The experimental equipment consists of a 1-mCi 137Cs source, 2×2 in. NaI detector with associated electronics and a multichannel analyzer. The normal data collection time is approximately 5 hours and the experiment is suitable for undergraduate laboratories.
Euler vectors and rotations about an arbitrary axis
Authors: Koehler T. R. , Trickey S. B.
Published: March 2005

We consider the relationships between the rotation matrix associated with a rotation through ϑ about an arbitrary axis and the Euler vector ϑ lying along that axis with magnitude ϑ.
Ladder operators for some spherically symmetric potentials in quantum mechanics
Authors: Newmarch J. D. , Golding R. M.
Published: March 2005

The energy levels of the free field, Coulomb potential, and the three-dimensional harmonic oscillator are found using the Dirac operator formalism by the construction of suitable ladder operators. The degeneracy of each level is also discussed.
Computer simulation of statistical plasma mechanics (an example of undergraduate research)
Authors: Theimer O. , Theimer M. M.
Published: March 2005

A plasma containing only a small number N?150 of electrons and ions in a cubical volume V=L3 is studied theoretically. The electrostatic potential energy UαN is computed for a large number 𝒩?20000 of random particle configurations, labeled α. The values UαN are used for determining the density of states GN(UN) and the thermal average ?N of the potential energy. Upper and lower limits for N and 𝒩 as functions of density and temperature are presented which show that the computer simulation is most convenient for high density, low temperature plasmas for which conventional analytical methods become very complicated. The properties of GN(UN) and ?N are discussed and it is demonstrated that ?N approaches the Debye-Hückel value UD in an oscillatory manner if the ratio L/λD increases beyond unity, where λD is the Debye shielding length. Suggestions for future work are made.
A simplified derivation of the Kubo-Greenwood formula
Authors: Moseley L. L. , Lukes T.
Published: March 2005

A simplified derivation of the Kubo-Greenwood-Peierls equation is given using the quantum theory of fluctuations developed by Callen and Welton.
Dynamics and time-averaged behavior of a molecular dissociation model
Authors: Falk H. , Wu Y.
Published: March 2005

The exact dynamics is presented for a two-particle model previously discussed within the framework of classical, equilibrium statistical mechanics. By expressing canonical ensemble averages in terms of time-energy averages a deeper understanding of the dissociation property is achieved.
Group theory of covariant harmonic oscillators
Authors: Kim Y. S. , Noz Marilyn E.
Published: March 2005

A simple and concrete example for illustrating the properties of noncompact groups is presented. This example is based on the covariant harmonic-oscillator formalism in which the relativistic wave functions carry a covariant-probability interpretation. It is shown that the lack of unitarity in a finite-dimensional representation corresponds to a Lorentz contraction of total probability. This paper gives a group-theoretical review of the oscillator formalism which was presented previously as a calculational tool for high-energy physics.
Relativistic harmonic oscillators and hadronic structures in the quantum-mechanics curriculum
Authors: Kim Y. S. , Noz Marilyn E.
Published: March 2005

A relativistic harmonic-oscillator formalism which is as mathematically simple as the nonrelativistic harmonic oscillator is given. The possibility of including this formalism in the first-year quantum-mechanics course is discussed. In view of its effectiveness in describing Lorentz-deformed hadrons, the inclusion of this formalism in a first-year graduate course will make the results of high-energy experiments more understandable to a larger number of physicists. A brief review of the past efforts to construct relativistic wave functions is also given.
Energy from the wind
Authors: Pelka David G. , Park Robert T. , Singh Runbir
Published: March 2005

The large-scale generation of electrical power by wind turbine fields is discussed. It is shown that the maximum power which can be extracted by a wind turbine is 16/27 or 59.3% of the power available in the wind. An estimate is made of the total electrical power which could be generated in the United States by utilizing wind energy. The material in this paper was presented by the authors in a one-semester course on energy science. It could also be used in an introductory physics class as an illustration of elementary fluid mechanics concepts and of the basic principles of energy and momentum conservation.
Matrix theory of small oscillations
Authors: Chavda L. K.
Published: March 2005

We present a complete matrix formulation of the theory of small oscillations. Simple analytic solutions involving matrix functions are found which clearly exhibit the transients, the damping factors, the Breit-Wigner form for resonances, etc.
Momentum autocorrelation functions from classical Green’s functions
Authors: Lottici P. P.
Published: March 2005

An elementary method based on the classical Green’s functions for the calculation of the momentum autocorrelation function for a harmonic oscillator and a damped harmonic oscillator is presented.
Cart wheels
Authors: Peck Edson R.
Published: March 2005

The name ’’cart wheels’’ here denotes two wheels rotating freely about a common axle and rolling on an inclined plane. This nonholonomic system is not new but appears to have been neglected. It makes a striking demonstration, and is useful for applying the methods of simple or advanced mechanics. When spinning, it travels horizontally with a small, superposed, circular motion, suggesting a linear counterpart of the precession and nutation of a gyroscope.
General theorems about homogeneous ellipsoidal inclusions
Authors: Korringa J. , Lin I-H. , Mills R. L.
Published: March 2005

Poisson’s theorem concerning the magnetization of a homogeneous body of ellipsoidal shape is analyzed. The polarization of a dielectric presents a mathematically equivalent problem, and also the transport of heat or electricity through an ellipsoid imbedded in a medium of different material properties is well known to lead to identical equations. The materials inside and outside the ellipsoid may be anisotropic with any orientation of the crystal axis. In all these problems the fields involved can be derived from a scalar potential. An analogous theorem applies to the elastic stress in an ellipsoidal inclusion. In this case the ’’potential’’ is the displacement vector. The proof that this generalizes to inclusions in crystalline media has been given only recently. We make a further generalization to the combined static effects of stress and internal fields and to combinations of linear transport phenomena. The key property in all these cases is that the infinite-space Green’s function for a point inside the ellipsoid, when integrated over the ellipsoid, yields a quadratic function of the coordinates of this point. We give two simple proofs of this property and show how it leads to the generalized Poisson theorem. The history of this problem is traced to Newton’s work on the equilibrium shape of a homogeneous rotating liquid body.
Diffusion of salt in tap water
Authors: Booth C. , Beer Tom , Penrose J. D.
Published: March 2005

We describe a simple experiment to measure the diffusion coefficient of a solute in a fluid. Laboratory-made floats are used to monitor the density changes associated with diffusion behavior. The experiment is ideally suited for undergraduate project work.
Binary elastic collision in velocity space
Authors: Piña E.
Published: March 2005

The binary elastic collision in velocity space is represented by an isosceles trapezoid, formed by the incoming and outgoing velocities of the particles. The relative velocities before and after collision are the diagonals of the trapezoid which intersect in the point corresponding to the velocity of the center of mass. The two parallel sides of the trapezoid have magnitudes which are in the mass ratio. The angles in the center of the mass frame and the laboratory frame are also represented in this trapezoid.
Pulsars in the classroom: Suggested exercises for lab or homework
Authors: Gordon Kurtiss J.
Published: March 2005

Exercises for introductory to intermediate level college students are proposed, in which observations of pulsars can be used to illustrate the phenomena of dispersion and Faraday rotation of radio waves, and to illustrate the differential rotation of the Galaxy. The article contains explanations of the phenomena and references to sources of appropriate observational data.
Monte Carlo simulation of Brownian motion with viscous drag
Authors: Gunther L. , Weaver D. L.
Published: March 2005

A model of Brownian motion which includes viscosity effects is discussed. The model lends itself to Monte Carlo simulation and thus is suitable for an elementary physics laboratory experiment. The more general aspects of the model are also discussed.
Maximizing the range of the shot put
Authors: Lichtenberg D. B. , Wills J. G.
Published: March 2005

We address the problem of the optimum angle at which a putter should release the shot in order to achieve maximum distance.
Pierre Gassendi, a forgotten but important man in the history of physics
Authors: Pancheri Lillian U.
Published: March 2005

Pierre Gassendi asserted, and for the first time successfully defended, the notion of an independently real space and time, thus providing seventeenth century physics with its needed philosophical foundation. His philosophical position allowed Gassendi to make advances in physics, especially with respect to gravity and the principle of inertia. Gassendi’s work was influential upon a number of persons, notably Boyle and Newton. This paper introduces the reader to Gassendi’s work in physics and philosophy and shows some of his relation to Galileo and his influence upon Newton.
Eddy currents: Levitation, metal detectors, and induction heating
Authors: Wouch G. , Lord A. E.
Published: March 2005

A metal object placed in the alternating magnetic field of a current distribution experiences a lifting force (electromagnetic levitation) and heating. These effects are caused by eddy currents induced in the metal. The eddy currents also change the inductance of the current generator. A simple and accessible calculation is given of these effects for a sphere in the field of a single circular loop of alternating current. Hopefully these simple calculations will help towards the inclusion of eddy current effects in the upper undergraduate physics E M syllabus.
Core-plus-branch plan for an introductory course
Authors: Newhall Herbert F.
Published: March 2005

The flexibility of a self-paced instructional format has been exploited to allow students in an introductory physics course to select part of the subject matter of the course. About 2/3 of each term of the course is devoted to the essential subject matter: the ’’core.’’ The format for the core part of the course is conventional. For the remainder of each term, a student pursues a ’’branch’’ topic of his choice. A self-paced format for the branch part of the course allows several branches to proceed simultaneously. The results of the first four years of experience with the core-plus-branch plan are described.
On the Lorentz-Dirac equation for a classical charged particle
Authors: Tirapegui E.
Published: March 2005

We present an elementary and simple derivation of the Lorentz-Dirac equation for a classical charged particle which clearly exhibits the origin of the mass renormalization one needs in this problem.
Figures of merit for energy conversion processes
Authors: Rubin Morton H.
Published: March 2005

In this paper we explore the problem of how to determine standards of performance for energy conversion processes. We briefly review the argument against the use of infintely slow reversible processes as standards, and explore some simple alternatives that take into account the desire to perform useful work in finite time. We illustrate these alternatives using an Atwood machine. In this simple case when the irreversibility is specified we show that the optimal efficiency for lifting a weight can be calculated for given performance goals (constraints).
Report on the use of follow-up orals in undergraduate and graduate physics teaching
Authors: Boedeker Richard R.
Published: March 2005

The use of orals as a follow-up to regular course exams is discussed. Data concerning student performances and attitudes toward the orals are given, along with a discussion of the different approaches that were used.
General treatment to calculate the Thevenin equivalent circuit
Authors: Domingo George
Published: March 2005

The method to calculate the Thevenin (or Norton) equivalent circuit of networks containing controlled current and/or voltage sources is identical to the method used with purely passive circuits if the fundamental concept of equivalence of networks is properly understood. The method is exemplified with passive and active networks including the emitter-follower circuit.
Kirchhoff’s laws of spectral analysis: A set of computer laboratory exercises
Authors: Fillmore James A. , Karp Alan H. , Mook Delo E.
Published: March 2005

A computer program which simulates an interstellar gas and dust cloud has been used to study Kirchhoff’s laws of spectral analysis in introductory astronomy courses. The model parameters can be varied to simulate various effects observed in actual clouds. Students are given exercises to use the program in a manner similar to a lab experiment.
Coherence: A simulation experiment
Authors: Jones Barrie W.
Published: March 2005

A simulation is described, the purpose of which is to elucidate the subject of coherence by a means which complements laboratory experiments. Coherence is linked to the correlation of fields using the specific case of the way the performance of a simple imaging system is sensitive to the coherence of the illumination. This sets the scene for the model on which the simulation is based. This model is described and some results presented.
Inertia demonstration revisited
Authors: Karioris Frank G.
Published: March 2005

The venerable inertia ball demonstration is briefly explained by a qualitative approach suitable for an introductory class. For the more advanced reader, it is shown that the system may be treated as a forced harmonic oscillator and the classical results of the demonstration are verified analytically. In addition, some surprises emerge because of nuances in the early response of the forced harmonic oscillator. Computer-generated graphs show that, paradoxically, the upper suspension cord may break when a rapid pull is applied to the lower cord and that it is theoretically possible for both cords to break simultaneously.
Calculation of the energy-band structure of the Kronig-Penney model using the nearly-free and tightly-bound-electron approximations
Authors: Wetsel Grover C.
Published: March 2005

The energy-band structure of noninteracting electrons in a one-dimensional crystal has been calculated using both exact and approximate methods for the case of a rectangular-well atomic potential. A comparison of the exact with the approximate solutions as a function of potential-well depth and ratio of lattice spacing to well width is presented. The results clearly demonstrate the successes, shortcomings, and range of applicability of the two extreme approximations (tightly-bound and nearly-free electrons). Such calculations form a coherent set of manageable problems which has been found to be an invaluable aid in the study of energy bands in a first-year graduate course in solid-state physics.
Precessional periods of long and short Foucault pendulums
Authors: Soga Michitoshi
Published: March 2005

The precessional period of a Foucault pendulum is derived without the usual assumption of small oscillation amplitudes. The periods for 100-m and 1-m pendulums with amplitudes of 1 m are essentially the same.
Coulomb’s law in a moving medium—a review exercise in advanced undergraduate electromagnetism
Authors: Sastry G. P.
Published: March 2005

The electromagnetic field of a static charge in a moving medium is evaluated using elements of special relativity, residue calculus, and Fourier integration. It is shown that this classical problem formally contains within it the rudiments of the magnetoelectric effect, spatial dispersion, and the angular spectrum of plane waves, which are topics of current research interest. A brief sketch of these topics is also included in this paper.
What the electromagnetic vector potential describes
Authors: Konopinski E. J.
Published: March 2005

An explicit physical interpretation of the electromagnetic vector potential is here pointed out—as field momentum available for exchange with kinetic momenta of charged matter. It is shown that the vector potential can be quite as directly measurable, without recourse to only quantum-mechanical effects, as are scalar potential differences and the force fields E, B. This suggests, in keeping with quantum electrodynamics, that the equations for potentials may be regarded as more ’’basic’’ than the Maxwell equations—but only because the potentials most directly represent interaction energy-momenta through which fields and charges become observable.
A laboratory experiment on the application of Stefan’s law to tungsten filament electric lamps
Authors: Prasad B. S. N. , Mascarenhas Rita
Published: March 2005

Commercially available electric lamps are used in a laboratory experiment for the verification of Stefan’s law. Assuming that the emissivity of tungsten filament remains constant and that all the filament power goes out as radiation, Stefan’s T4 law can be verified from a log-log plot of radiated power P against temperature T of the filament. It is found that correction to filament power due to convection loss is necessary for the gas-filled lamps and not for vacuum lamps. The experimental value of the slope of the graph of log P vs log T for all these lamps is found to be 5, which shows that the emissivity of the filament surface is proportional to the temperature of the filament. A simplified laboratory experiment avoiding temperature calculations and convection loss corrections is described in this study.
Tunneling—how it all started
Authors: Condon E. U.
Published: March 2005

A personal account of the early history of tunneling and the contribution of Ronald W. Gurney.
Can individual elementary particles have individual properties?
Authors: Belinfante Frederik J.
Published: March 2005

Assuming the validity of conventional quantum theory, we may divide the laws of physics into laws of conservation and laws of change. The former, unmodified by quantum theory, are deterministic. The latter, according to quantum theory, are indeterministic for single systems, but curiously are deterministic for probability distributions in ensembles of particles. Elementary particles are characterized by invariant properties which are conserved. The question is discussed whether noninvariant observables, like momentum or spin components, at some chosen time can have definite instantaneous values. For investigating this, we discuss a simplified version of a thought experiment proposed some years ago by Wigner. This provides some answers to two questions: (1) In what sense is it usually insufficient to describe a beam of equally prepared particles as a collection of particles with certain given properties, instead of describing this beam by waves or by a state vector? (2) In case we know what value an observable has for a particle, when may it be useful to describe this individual particle quantum mechanically by ascribing to it the corresponding eigenfunction as its individual state vector?
Surface effects and the density of states of electrons in a semi-infinite array of identical potentials
Authors: Wu S. Y. , Wu D. C.
Published: March 2005

The relationship between the surface effects and the boundary conditions of a semi-infinite array of identical potentials has been studied. It is found that the appearance of the surface states hinges on the appropriate consideration of the possible effects on atoms near the surface due to the presence of the surface. Criteria for the existence of the surface states for two specific models of the surface are obtained.
Relativistic two-body electrodynamics
Authors: Stephas Paul
Published: March 2005

The few known analytic solutions for the special-relativistic two-body electrodynamic problem are presented. The point particles interact by relativistic action-at-a-distance forces without radiation reaction, for both time-symmetric and time-asymmetric interactions. For ease of understanding by those not specialists in relativity, standard vector notation is used, avoiding metrics. Recipes are given for obtaining the conserved quantities, four-momentum, angular momentum tensor, and dilation, directly from the equations of motion and without recourse to action principles.
Basic properties of certain types of operators: A unified treatment
Authors: Roy C. L.
Published: March 2005

Using normal operators as a common footing, the basic properties of Hermitian operators, unitary operators, and anti-Hermitian operators are treated from a unified viewpoint. The interlinks among the eigenvalues of these operators are elucidated with the help of suitable prescriptions for mapping in the plane of complex eigenvalues. Further, we show that some of the characteristics of Hermitian operators hold good under a perspective which is broader than the defining criterion for Hermitian operators.
On the high-temperature expansion of the density matrix
Authors: Onofri Enrico
Published: March 2005

The high-temperature expansion of the density matrix e−βH is derived in an elementary way, which avoids use of the Feynman-Kac formula. The expansion provides an elementary introduction to such topics as the interaction representation, Wick’s theorem, and the functional representation of the Green’s function.
Can the effect precede its cause in classical electrodynamics?
Authors: Grünbaum Adolf , Janis Allen I.
Published: March 2005

In classical electrodynamics, the imposition of Dirac’s asymptotic boundary condition on the differential equation of motion for a charged particle leads to the prediction of preacceleration; that is, the particle’s acceleration at time t depends on external forces acting at times later than t. Since force is usually considered to be the cause of acceleration rather than vice versa, the existence of this preacceleration has been taken to show that an effect can precede its cause. In this paper it is argued that such a retrocausal interpretation of preacceleration is either unfounded or false.
Derivation of Maxwell’s equations from the local gauge invariance of quantum mechanics
Authors: Kobe Donald H.
Published: March 2005

Maxwell’s equations are derived from the principle of form invariance of quantum mechanics under multiplication of the wave function by a space- and time-dependent phase factor (local gauge transformations of the first kind). The principle leads to the introduction of the vector and scalar potentials, which are shown to transform under the usual gauge transformations of electromagnetism (gauge transformations of the second kind). The electric and magnetic fields are introduced in the usual way to obtain observable fields which are gauge independent. Faraday’s law and the condition of no magnetic monopoles are obtained from the gauge transformations of the potentials. Conservation of energy and the linearity of the field equations are assumed to obtain Gauss’ law and the Ampere-Maxwell law.
Electrostatic potential energy leading to an inertial mass change for a system of two point charges
Authors: Boyer Timothy H.
Published: March 2005

The system of two charged point particles traveling side by side at arbitrary velocity less than the speed of light and accelerating slowly is analyzed within classical electromagnetism as to the connection between the electrostatic potential energy of the system and the inertial mass. The total external force necessary to accelerate the system is calculated, and it is found that the change of system mass associated with the electrostatic potential energy of the two particles is accounted for exactly by the electromagnetic force of one charged particle on the other during the acceleration. The example provides a striking illustration and detailed mechanism for understanding the mass-energy idea associated with special relativity.
Simple derivation of the diffusion equation from the Fokker-Planck equation using perturbation methods
Authors: D’Arruda José , Larsen Edward W.
Published: March 2005

In the paper, we develop an alternate formulation of the diffusion or Smoluchowski equation in the framework of asymptotic perturbation analysis. With the Fokker-Planck equation as our starting point, and with the assumption of small mean free paths, an explicit scaling of the time coordinate makes this derivation especially suited for classroom use.
Esoteric elementary particle phenomena in undergraduate physics—spontaneous symmetry breaking and scale invariance
Authors: Greenberger Daniel M.
Published: March 2005

We take two rather abstract concepts from elementary particle physics, and show that there actually exist analogs to both of them in undergraduate physics. In the case of spontaneous symmetry breaking, we provide an example where the most symmetrical state of a simple system suddenly becomes unstable, while a less symmetrical state develops lower energy and becomes stable. In the case of scale invariance, we consider an example with no natural scale determined, and show that a straightforward dimensional analysis of the problem leads to incorrect results, because of the occurrence of infinities, even though they would appear to be irrelevant infinities that might not be expected to affect the dimensions of the answer. We then show how a simple use of the scale invariance of the problem leads to the correct answer.
Measurement of thermoelectric effects at low temperature
Authors: Guénault A. M. , Lawson N. S. , Veazey S. D.
Published: March 2005

A method, suitable for an advanced undergraduate project laboratory, is described whereby the existence of the Seebeck, Peltier, and Thomson effects may be demonstrated in a single experimental setup using a Cu–0.01%Fe sample. Experimental results for the Peltier and Thomson coefficients are obtained which are consistent with the Kelvin relations. The experiment provides the student with a convenient introduction to the use of liquid helium as well as to the procedural and measuring techniques employed at low temperatures.
Multipole radiation theory in an upper-level undergraduate physics course
Authors: Haskins J. Richard
Published: March 2005

Aspects of multipole radiation theory are presented at a level suitable for a senior course in nuclear physics. Selection rules, dependence on photon energy, polarizations, and radiation patterns are treated for E1, M1, and E2 multipoles.
Particles falling in a rotating fluid
Authors: Wick Gerald L.
Published: March 2005

Particles falling in a fluid rotating about a horizontal axis can go into quasistable orbits. An analytical solution of the particle’s motion is derived. This model may be applicable to suspension of diatoms and other particles in the ocean.
Pendulum on a massive cord
Authors: Montgomery C. G.
Published: March 2005

The oscillation frequency of a pendulum supported by a massive string, discussed previously by Armstrong, is analyzed both analytically and using a variational method. The variational approach displays its characteristic benefits in providing both an efficient computational procedure and also useful insight into the physical behavior of the system.
Bouncing ball experiment
Authors: Maurone Philip A. , Wunderlich Francis J.
Published: March 2005

The results of an analysis of two target surfaces used in a bouncing ball experiment are presented. It is shown that if a ball is dropped onto a flat surface with an initial spin, or component of velocity horizontal to the surface, the ball will travel horizontally in ’’one direction’’ while it executes multiple bounces. Because of this phenomenon, the ball will eventually fall off any reasonably sized flat target surface. To overcome this, we consider a surface with a conical depression in it so as to ’’focus’’ or localize the bouncing ball. Equations that describe the motion on such a surface are presented.
Force field inside a magnet
Authors: Wolff Peter A.
Published: March 2005

In the vacuum the magnetic field is defined by the force law f=qv×B=qv×μ0H. Within material media, however, the fields are usually defined by Maxwell’s equations, and it is an experimental question whether B or μ0H is the force field. If the macroscopic fields are assumed to be averages of microscopic fields whose sources are dipoles, it is shown that these averages depend strongly on the nature of the microscopic dipoles. For dipoles consisting of current loops, B is the force field; for dipoles consisting of pairs of monopoles μ0H is the force field.
Sublimation of moth balls
Authors: Tennakone K. , Peiris M. G. C.
Published: March 2005

The study of the decay of a moth ball due to sublimation is an instructive exercise in physics which demonstrates diffusion phenomena. The rate at which a moth ball exposed to the atmosphere wears away due to sublimation is calculated. Experiments are given to demonstrate the validity of the calculation.
A simple derivation of the bandwidth of a laser oscillator
Authors: Anderson L. W. , Lawler J. E.
Published: March 2005

A simple derivation of the minimum possible bandwidth for a laser oscillator is given. This derivation stresses the role of spontaneous emission in limiting the bandwidth of the oscillator.
Hard-core potentials in quantum mechanics
Authors: Downs B. W. , Ram Budh
Published: March 2005

The treatment of hard-core potentials in quantum mechanics is described. Known techniques and results are collected and discussed here so that they may be readily available. Two-body bound-state and scattering problems are considered in some detail. The use of hard-core potentials in analyses of more complicated systems is indicated.
Multipole expansions of electromagnetic fields using Debye potentials
Authors: Gray C. G.
Published: March 2005

The Debye potentials are introduced by giving new derivations of the multipole expansions of the magnetostatic and electrostatic fields. Simplified derivations of the multipole expansions of the electrodynamic fields are then given. The radiated energy, momentum, and angular momentum are all calculated in the same manner, i.e., using the proper transport equations. The questions of uniqueness and completeness of the Debye potential representations of the fields are discussed. In the Appendices are collected together some useful vector field theorems and operator identities involving the angular momentum operator, and also simplified derivations of the spherical harmonic expansions of the static and dynamic Green functions.
The positivity of an integral connected with the helium atom problem
Authors: Morgan John D.
Published: March 2005

A simple proof of the positivity of an integral which arose in J. H. Bartlett, Jr.’s treatment of the helium atom problem is presented. It is suggested that the technique used may have applications to similar complicated integrals.
Graphical method for antiferromagnetic susceptibility
Authors: Whitaker M. A. B.
Published: March 2005

A graphical method is developed for studying the parallel susceptibility of an antiferromagnetic material. The graphical result conveys information more readily than the algebraic formulas, and the treatment brings out both the similarities between ferromagnetism and antiferromagnetism as well as their important differences.
The Mathematical Association of America
Authors: Alder Henry L.
Published: March 2005

The activities and publications of the Mathematical Association of America, especially those of interest to physicists, are described by its president for his colleagues in physics.
Hawthorne effect and quality teaching: Training graduate teaching assistants to teach
Authors: Armenti Angelo , Wheeler Gerald F.
Published: March 2005

In this paper we describe our experience with a course entitled ’’Practicum in the Teaching of Physics’’ which was designed to improve the teaching of physics by lab instructors (TA’s) in undergraduate laboratory classes. Although revised and refined over the last six years, the basic concept of the course involving the ’’videotape experience’’ has been retained with tremendous sucess. The possible connection between the success of this course and the famous ’’Hawthorne experiment’’ of Elton Mayo is explored. If valid, this connection has deep and far-ranging consequences for the teaching profession in general and physics teaching in particular.
On the mathematical theory of clock escapements
Authors: Kesteven M.
Published: March 2005

A novel solution is presented to the problem of evaluating the influences of a clock escapement on the pendulum’s period. The conclusions are in general agreement with those of previous authors.
Photoelectric effect revisited (or an inexpensive device to determine h/e)
Authors: Boys Donald W. , Cox Mary E. , Mykolajenko William
Published: March 2005

A novel and inexpensive device for introductory students to measure Planck’s constant using the photoelectric effect has been developed. Quasimonochromatic light illuminates the photocathode. An inexpensive voltage follower circuit with high impedance and low capacitance is used to determine the stopping potential, which is read on a standard voltmeter. The results agree to within ±5% of the currently accepted value. The experimental results are highly reproducible.
A simplified version of Carathéodory thermodynamics
Authors: Marshall T. W.
Published: March 2005

Starting from the existence of adiabiatic surfaces for a thermodynamic system, we show, by coupling it to a perfect gas, that the absolute temperature is an integrating factor of the reversible heat input. The proof makes no use of the general theory of Pfaffians.