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Carl Mungan, United States Naval Academy
On page 293 of the May 2017 issue of The Physics Teacher (http://aapt.scitation.org/journal/pte) a trio of Japanese educators propose an improved motor design consisting of coiled copper wire suspended on clips above a permanent magnet. Rather than the conventional design which uses a single coil and thus requires a commutator (by stripping the insulation off only one side of the copper wire) and priming (by giving the coil an initial twist to start it), the new design uses a figure-8 pair of coils to avoid those two issues and to increase the energy conversion efficiency. The September 2017 issue has a large number of thought-provoking articles about the issue of racial diversity in physics education.
Pantaleone analyzes the wondrous chain foundation on page 414 of the June 2017 issue of the American Journal of Physics (http://aapt.scitation.org/journal/ajp). His key idea is that as a link is pulled up at an angle from the pile, there is an upward reaction force from the pile on that link. Digilov uses the Lambert W function to analyze the time-dependent weight of a vessel from which liquid is draining out through a capillary tube on page 510 of the July issue. On page 522 of the same issue, three Brazilian physicists present an undergraduate experiment to measure thermal lensing of a Gaussian laser beam in soy sauce. A group at Smith College notes on page 663 in the September issue that the gravitational self-interaction of earth’s tidal and terrestial bulges produce a substantial correction to the conventional values; a helpful analogy is drawn to the solution of Laplace’s equation for a charged shell.
Article 043004 in the July 2017 issue of Physics Education uses a unipolar motor to demonstrate angular momentum conservation; article 043006 emphasizes that the stopping potential in the photoelectric effect determines the work function of the collector and not of the emitter; and article 045021 discusses the theoretical upper limit on the possible mass of stars. Article 045402 in the July 2017 issue of the European Journal of Physics revisits the issue of the difference between the standard expressions for the phase velocity of a free matter wave in the relativistic and classical limits, and why both disagree with the particle velocity. Article 055202 in the September issue discusses the problem of determining the static charge distribution along a finite straight wire; I was surprised to learn this simple configuration is unsolved and possibly indeterminate. Both journals can be found online starting at http://iopscience.iop.org/journalList.
The June 2017 issue of Resonance has an article about radio-frequency identification tags and another about orbital precession due to the general theory of relativity. The July issue has a paper about using interferometry to measure the diameter of stars, as first performed by Michelson. The August issue has a historical review of density functional theory. Finally the September issue discusses some experiments with antibubbles, which are spherical shells of air floating in a soap solution. These articles can be freely accessed at http://www.ias.ac.in/listing/issues/reso.
A Python program to solve Schrödinger’s equation is presented on page 813 of the June 2017 issue of the Journal of Chemical Education. An editorial on page 825 of the July issue discusses two recent studies which show no evidence that instruction tailored to particular student learning styles results in improved achievement; an article on page 976 of the same issue explains how to construct the periodic table step by step based on atomic orbitals. Synthesis and characterization of carbon and of perovskite quantum dots are respectively discussed on pages 1143 and 1150 of the August issue. The journal archives are at http://pubs.acs.org/loi/jceda8.
Article 010130 in Physical Review Physics Education Research at https://journals.aps.org/prper/pdf/10.1103/PhysRevPhysEducRes.13.010130 discusses the pedagogical implications of the distinction between the gravitational definition of weight (as the net gravitational force acting on an object) and the operational defintion (as the contact force measured by a scale). Article 020110 at https://journals.aps.org/prper/pdf/10.1103/PhysRevPhysEducRes.13.020110 considers student views about the nature and process of experimental physics compared to those of practicing physicists.
An article published online on 14 September 2017 in the Journal of Modern Optics at http://www.tandfonline.com/doi/full/10.1080/09500340.2017.1374482 shows that the Doppler shift in the emission frequency of a moving atom gives rise to a velocity-dependent frictional force, in apparent contradiction to relativity. (The velocity of the atom and hence the force depends on the motion of the observer.) This paradox is explained by the change in momentum due to the relativistic loss in mass of the atom when it radiates away a photon, making for an alternative method of deducing Einstein’s mass-energy relation.
Disclaimer – The articles and opinion pieces found in this issue of the APS Forum on Education Newsletter are not peer refereed and represent solely the views of the authors and not necessarily the views of the APS.