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Dec 2005

Volume 73, Issue 12, pp. 1093-1198

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John S. Rigden Citation Robert A. Millikan Award for 2005

Jim Nelson, Past-President AAPT

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1093

Online Publication Date: Nov 2005

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Abstract Unavailable
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01.40.-d Education
01.10.Cr Announcements, news, and awards

The mystique of physics: Relumine the Enlightenment

John S. Rigden

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1094 | Cited 3 times

Online Publication Date: Nov 2005

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There is a mystique to physics because people are inherently receptive to the qualities that make physics special. It is this receptivity and the resulting mystique that makes Einstein the standard of greatness. However, neither the mystique nor the receptivity can be taken for granted. The near-reverent confidence that people have afforded physics is currently being challenged. What does this suggest for the physics classroom?
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01.40.-d Education
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Visualization of induced electric fields

A. P. J. van Deursen

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1099 | Cited 1 time

Online Publication Date: Nov 2005

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A cylindrical electrolytic tank between a set of Helmholtz coils provides a classroom demonstration of induced, nonconservative electric fields. The field strength is measured by a sensor consisting of a pair of tiny spheres immersed in the liquid. The sensor signal depends on position, frequency, and orientation. A low resistance copper ring strongly modifies the magnetic field inside and increases the field outside; the electric field changes accordingly. A metallic ring with a small gap can be used to measure the behavior of the electric field in the vicinity of windings around a transformer core. The measured results are consistent with simple models.
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01.50.My Demonstration experiments and apparatus
41.20.-q Applied classical electromagnetism
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Fun with stacking blocks

John F. Hall

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1107 | Cited 1 time

Online Publication Date: Nov 2005

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How can a given number of rigid, rectangular blocks be stacked in a planar arrangement to produce the maximum overhang over a support edge? To answer this question, three cases of increasing complexity are considered: single-wide stacks, multiwide stacks that do not rely on friction, and multiwide stacks that do rely on friction. The solution to the first case has existed for more than 150 years; the answer to the second case is attempted in this paper; and the considerable complexity of the third is demonstrated. Many mathematical aspects of block stacking are discussed, and a new challenge is posed. The analysis uses the principles of static equilibrium and stability and free body diagrams, key concepts in classical mechanics.
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01.50.-i Educational aids
45.05.+x General theory of classical mechanics of discrete systems

The Minkowski metric in non-inertial observer radar coordinates

E. Minguzzi

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1117 | Cited 1 time

Online Publication Date: Nov 2005

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We give a closed expression for the Minkowski (1+1)-dimensional metric in the radar coordinates of an arbitrary non-inertial observer O in terms of O’s proper acceleration. Knowledge of the metric allows the non-inertial observer to perform experiments in spacetime without making reference to inertial frames. To clarify the relation between inertial and non-inertial observers the coordinate transformation between radar and inertial coordinates also is given. We show that every conformally flat coordinate system can be regarded as the radar coordinate system of a suitable observer for a suitable parametrization of the observer worldline. Therefore, the coordinate transformation between arbitrarily moving observers is a conformal transformation and conformally invariant (1+1)-dimensional theories lead to the same physics for all observers, independently of their relative motion.
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01.50.-i Educational aids
03.30.+p Special relativity

A damped pendulum forced with a constant torque

P. Coullet, J. M. Gilli, M. Monticelli, and N. Vandenberghe

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1122 | Cited 5 times

Online Publication Date: Nov 2005

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The dynamics of a damped pendulum driven by a constant torque is studied experimentally and theoretically. We use this simple device to demonstrate some generic dynamical behavior including the loss of equilibrium or saddle node bifurcation with or without hysteresis and the homoclinic bifurcation. A qualitative analysis is developed to emphasize the role of two dimensionless parameters corresponding to damping and forcing.
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01.50.-i Educational aids
46.40.Ff Resonance, damping, and dynamic stability
07.10.-h Mechanical instruments and equipment
05.45.-a Nonlinear dynamics and chaos

Fluctuation correlation spectroscopy for the advanced physics laboratory

Robert Rieger, Carlheinz Röcker, and G. Ulrich Nienhaus

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1129 | Cited 7 times

Online Publication Date: Nov 2005

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A fluorescence correlation spectrometer is developed that is suitable for use in advanced laboratory courses. The instrument is simple to build and understand and can be constructed at a small fraction of the cost of a commercial or research-grade instrument. We demonstrate its surprisingly high performance with a simple biophysics application, the study of the binding of two complementary DNA strands. The instrument will be useful in areas of physics where precise measurements of the dynamics of fluorescent (or fluorescently labeled) molecules or nanoparticles in solution are of interest.
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01.50.Pa Laboratory experiments and apparatus
01.50.Qb Laboratory course design, organization, and evaluation
87.15.M- Spectra of biomolecules
07.60.Rd Visible and ultraviolet spectrometers

Construction and calibration of a low cost Fabry-Perot interferometer for spectroscopy experiments

Colin D. Fletcher and Chad Orzel

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1135

Online Publication Date: Nov 2005

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We describe the construction and calibration of a low cost confocal scanning Fabry-Perot interferometer with a free spectral range of 382.3±1.1 MHz, which is suitable for use as a frequency reference in laser locking and for spectroscopy experiments. The calibration of the free spectral range is performed using the longitudinal modes of a commercial helium–neon laser.
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01.50.Pa Laboratory experiments and apparatus
07.60.Ly Interferometers
42.79.Bh Lenses, prisms and mirrors

Thermodynamic derivations of the mechanical equilibrium conditions for fluid surfaces: Young’s and Laplace’s equations

P. Roura

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1139 | Cited 10 times

Online Publication Date: Nov 2005

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The fundamental laws governing the mechanical equilibrium of solid-fluid systems were formulated in 1805 and 1806. They are Laplace’s law, which describes the pressure drop across an interface, and Young’s equation for the contact angle. At that time, these laws were justified on purely mechanical grounds. In 1880 Gibbs used thermodynamics to show that these laws were necessary conditions for the equilibrium of heterogeneous systems. We revisit Gibbs’ derivation and simplify it for possible use at the undergraduate level. In addition, we present derivations of Young’s and Laplace’s equations, which involve energy balance on a volume element located at the surface. In particular, it is shown that the derivations are simpler, allow the analysis of nonequilibrium situations, and give a natural identification of the surface energy with the surface tension of the liquid-vapor interface.
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01.50.-i Educational aids
68.03.Cd Surface tension and related phenomena

Simple analytical models of gravitational collapse

R. J. Adler, J. D. Bjorken, P. Chen, and J. S. Liu

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1148 | Cited 11 times

Online Publication Date: Nov 2005

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Most general relativity textbooks devote considerable attention to the simplest example of a black hole containing a singularity, the Schwarzschild geometry. Only a few discuss the dynamical process of gravitational collapse by which black holes and singularities form. We present two simple analytical models that describe this process. The first involves collapsing spherical shells of light and is analyzed mainly in Eddington-Finkelstein coordinates; the second involves collapsing spheres filled with a perfect fluid and is analyzed mainly in Painleve-Gullstrand coordinates. Our main goal is simplicity and algebraic completeness, but we also present a few more sophisticated results such as the collapse of a light shell in Kruskal-Szekeres coordinates.
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01.50.-i Educational aids
95.30.Sf Relativity and gravitation
04.20.Ha Asymptotic structure
04.70.Dy Quantum aspects of black holes, evaporation, thermodynamics
97.60.Lf Black holes

Simple derivation of general Fierz-type identities

C. C. Nishi

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1160 | Cited 9 times

Online Publication Date: Nov 2005

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General Fierz-type identities are examined and their well-known connection with completeness relations in matrix vector spaces is shown. In particular, I derive the chiral Fierz identities in a simple and systematic way by using a chiral basis for the complex 4×4 matrices. Other completeness relations for the fundamental representations of SU(N) algebras can be extracted using the same reasoning.
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01.40.-d Education
02.20.Qs General properties, structure, and representation of Lie groups
02.10.Yn Matrix theory
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Student understanding of induced current: Using tutorials in introductory physics to teach electricity and magnetism

Heidi V. Mauk and Dan Hingley

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1164

Online Publication Date: Nov 2005

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Previous research indicates significant improvement in student conceptual understanding of physics topics after instruction with Tutorials in Introductory Physics at the University of Washington, Seattle, Washington. However, assessment of the effectiveness of tutorials at other institutions is crucial. We conducted such a field test at the United States Air Force Academy, Colorado. Students using the tutorials were compared to students using the standard curriculum, students using tutorial pretests only, and students in the honors program. Assessment was based on conceptual questions involving induced current and force. Our results show that students using the tutorials in a modified setting outperformed the control group and rose to the level of performance of the honors students. Our analysis of student reasoning indicates areas where further development of the tutorials is warranted.
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01.50.Kw Techniques of testing

Interpreting FCI scores: Normalized gain, preinstruction scores, and scientific reasoning ability

Vincent P. Coletta and Jeffrey A. Phillips

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1172 | Cited 23 times

Online Publication Date: Nov 2005

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We examined normalized gains and preinstruction scores on the force concept inventory (FCI) for students in interactive engagement courses in introductory mechanics at four universities and found a significant, positive correlation for three of them. We also examined class average FCI scores of 2948 students in 38 interactive engagement classes, 31 of which were from the same four universities and 7 of which came from 3 other schools. We found a significant, positive correlation between class average normalized FCI gains and class average preinstruction scores. To probe this correlation, we administered Lawson’s classroom test of scientific reasoning to 65 students and found a significant, positive correlation between these students’ normalized FCI gains and their Lawson test scores. This correlation is even stronger than the correlation between FCI gains and preinstruction FCI scores. Our study demonstrates that differences in student populations are important when comparing normalized gains in different interactive engagement classes. We suggest using the Lawson test along with the FCI to measure the effectiveness of alternative interactive engagement strategies.
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01.50.-i Educational aids
45.05.+x General theory of classical mechanics of discrete systems
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Sequential measurements and the commutator

P. B. Siegel

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1183

Online Publication Date: Nov 2005

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Abstract Unavailable
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01.50.-i Educational aids
03.65.-w Quantum mechanics

Relativity, energy flow, and hidden momentum

Timothy H. Boyer

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1184 | Cited 1 time

Online Publication Date: Nov 2005

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Abstract Unavailable
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01.40.-d Education
03.30.+p Special relativity
45.05.+x General theory of classical mechanics of discrete systems
03.50.De Classical electromagnetism, Maxwell equations
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Protein gel electrophoresis in the undergraduate physics laboratory

Danny G. Miles, Jr., David W. Bushman, and Zhong-Ying Chen

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1186

Online Publication Date: Nov 2005

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We describe an undergraduate laboratory experiment in protein gel electrophoresis that uses readily available apparatus and materials. The separation of a mixture of stained proteins by gel electrophoresis was videotaped. Position–time data for the proteins generated from analysis of digitized videotape images allowed for calculation of protein terminal velocities. The dependence of protein terminal velocity on molar mass was determined and found to agree with predictions made by current theory. We also introduce a model that draws on simple physical concepts to help students place the experimental results in context.
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01.50.Pa Laboratory experiments and apparatus
87.15.Tt Electrophoresis
82.70.Gg Gels and sols

Correlation detection of fluorescent lamp flicker using a sound card

Guang-Hui Tang and Jiang-Cheng Wang

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1189 | Cited 1 time

Online Publication Date: Nov 2005

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Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
42.72.Bj Visible and ultraviolet sources
85.60.Dw Photodiodes; phototransistors; photoresistors

Spontaneous magnetization of ferromagnets

Yaakov Kraftmakher

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1191

Online Publication Date: Nov 2005

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Computer-controlled experiments are described for observing hysteresis loops of a ferromagnet over a wide temperature range, including its Curie point, and for determining the temperature dependence of the spontaneous magnetization. A nickel-based alloy, Monel 400, is used as the sample.
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01.50.Pa Laboratory experiments and apparatus
01.50.Lc Laboratory computer use
75.50.Cc Other ferromagnetic metals and alloys
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

What does the voltmeter read?

Howard W. Nicholson

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1194

Online Publication Date: Nov 2005

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A relatively simple experimental apparatus that uses an ac voltmeter to demonstrate the undefined nature of voltage when ∲E⋅dl≠0 is described. This apparatus is suitable for a lecture demonstration in introductory physics courses. Voltmeter readings obtained in different experimental circumstances are also briefly discussed.
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01.50.My Demonstration experiments and apparatus
01.40.G- Curricula and evaluation
07.68.+m Photography, photographic instruments; xerography
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Introductory Quantum Optics.

Christopher C. Gerry, Author, Peter L. Knight, Author, and Mark Beck, Reviewer

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1197

Online Publication Date: Nov 2005

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Abstract Unavailable
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01.30.Vv Book reviews
01.40.-d Education

BOOKS RECEIVED

American Journal of Physics -- December 2005 -- Volume 73, Issue 12, pp. 1198

Online Publication Date: Nov 2005

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Abstract Unavailable
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01.30.Vv Book reviews
01.40.-d Education
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