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Sep 2007

Volume 45, Issue 6, pp. 326-399

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No-Shock Alternative

Dick Heckathorn

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 326

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.Pa Laboratory experiments and apparatus
01.40.J- Teacher training

Physics First, Chemistry and Biology

Leon Lederman, Resident Scholar

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 326

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.40.ek Secondary school
01.40.Di Course design and evaluation
01.75.+m Science and society

European-Type Physics Plan

Bill Franklin

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 326

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.40.ek Secondary school
01.40.gb Teaching methods and strategies
01.75.+m Science and society

The Elastic Constant

Kenneth A. Pestka, II

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 327

Online Publication Date: Aug 2007

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01.40.gb Teaching methods and strategies
01.40.J- Teacher training
01.50.Pa Laboratory experiments and apparatus

Tacoma Narrows Bridge

J. Terrence Klopcic, Director of Laboratories

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 327

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.85.+f Careers in physics and science
01.40.gb Teaching methods and strategies
01.50.-i Educational aids

The Real Story

Raymond H. Hahn

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 328 | Cited 2 times

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.40.J- Teacher training
01.50.F- Audio and visual aids
01.55.+b General physics

Physics Respresentations

Bob Baker

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 328

Online Publication Date: Aug 2007

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01.40.J- Teacher training
01.40.gb Teaching methods and strategies

Lorentz Transformation and Charge Conservation

Elisha Huggins and Drew Milsom

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 328 | Cited 3 times

Online Publication Date: Aug 2007

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01.40.Ha Learning theory and science teaching
01.40.Fk Research in physics education
01.40.J- Teacher training
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Remembering Dick Crane

E. Leonard Jossem

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 330

Online Publication Date: Aug 2007

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Physicist, polymath, educator, leader, Horace Richard Crane died on April 19, 2007, a few months short of his 100th birthday. Those of us who were fortunate enough to have had him as a friend mourn his loss, but for all of us he leaves a rich and varied legacy of published works that invite reading and rereading.
Dick's work as a physicist was recognized in 1966 by his election to the National Academy of Sciences and in 1986 by the award of the President's National Medal of Science: “For the first measurement of the magnetic moment and spin of free electrons and positrons.”
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01.60.+q Biographies, tributes, personal notes, and obituaries
01.40.J- Teacher training
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BALANCED BROOM

Paul Hewitt

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 332

Online Publication Date: Aug 2007

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01.50.-i Educational aids
01.55.+b General physics
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Aerodynamics of a Party Balloon

Rod Cross

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 334 | Cited 4 times

Online Publication Date: Aug 2007

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It is well-known that a party balloon can be made to fly erratically across a room, but it can also be used for quantitative measurements of other aspects of aerodynamics. Since a balloon is light and has a large surface area, even relatively weak aerodynamic forces can be readily demonstrated or measured in the classroom. Accurate measurements can be made of drag and buoyant forces, and reasonable estimates can also be made of the Magnus force on a spinning balloon.
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01.50.My Demonstration experiments and apparatus
47.00.00 Fluid dynamics

Caught in the Draft

Ron Edge

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 338 | Cited 1 time

Online Publication Date: Aug 2007

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We've all seen (in movies, newscasts, or perhaps in person) the violent effect of the downwash that occurs when a helicopter hovers over the ground. Leaves, grass, and debris are dramatically blown about. We've also sat in front of circulating room fans and felt a large draft, whereas there seems to be very little air movement behind the fan. The cause of this is a delightful manifestation of Bernoulli's principle. The fan blades, or helicopter rotor blades, produce a pressure differential as air passes through them—let us say p1 before and p2 after, as shown in Fig. 1, with p2 greater than p1. If p0 is the ambient pressure, Bernoulli's equation gives
math
where v1 is the velocity of the air entering the fan. Continuity requires that v2 leaving the fan must equal v1 entering the fan for an incompressible fluid, approximately true here (Av1 = Av2, where A is the area swept out by the blades, the “rotor disk area”). However, some distance below the rotor (or in front of the fan) the velocity is vd (vdowndraft in the figure) and the pressure again p0, so Bernoulli gives us
math
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01.40.J- Teacher training
01.50.-i Educational aids
47.00.00 Fluid dynamics
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Inquiry with Laser Printer Diffraction Gratings

Stephen J. Van Hook

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 340 | Cited 1 time

Online Publication Date: Aug 2007

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The pages of The Physics Teacher have featured several clever designs for homemade diffraction gratings using a variety of materials—cloth,1 lithographic film,2 wire,3 compact discs,4 parts of aerosol spray cans,5 and pseudoliquids and pseudosolids.6 A different and inexpensive method I use to make low-resolution diffraction gratings takes advantage of specialty transparency film designed for use with laser printers. A standard laser printer can print black lines (separated by a white line) at 60 black lines∕cm (about 150 lines∕in), which is a small enough spacing to produce a crude diffraction grating [see Fig. 1(a)] that is sufficient for the physics inquiry activities described in this paper.
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01.50.My Demonstration experiments and apparatus
01.50.Pa Laboratory experiments and apparatus
42.00.00 Optics

Squiggle Ball Capture: A Simple, Visual Kinetic Theory Experiment

Tim Gfroerer and Ken Rathbun

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 344

Online Publication Date: Aug 2007

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When particles move about randomly in the presence of traps, how long does it take for them to be captured? Well, it depends on the average speed of the particles and the dimensions and distribution of the traps. For example, when neutrons are generated in nuclear fission reactions, they must be captured by other fissionable nuclei in order to sustain a chain reaction. But we learn in introductory physics that these energetic neutrons are traveling at enormous speeds and must be slowed to increase the time that they spend in the vicinity of the nuclei. While the capture of “thermal” particles into lower energy states is an important physical process, it is difficult to simulate macroscopically. For example, where do you get a collection of macroscopic objects that have the means to sustain random motion? Enter Squiggle Balls™—inexpensive spherical cat toys that use a battery-powered motor and asymmetric rotor to roll and tumble happily about.1 Put a few on a bounded, elevated platform with several circular holes, and you have an ideal macroscopic system for exploring the world of capture.
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01.50.Pa Laboratory experiments and apparatus
05.00.00 Statistical physics, thermodynamics, and nonlinear dynamical systems
47.00.00 Fluid dynamics

Measuring the Forces Between Magnetic Dipoles

Lisa E. Gayetsky and Craig L. Caylor

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 348 | Cited 3 times

Online Publication Date: Aug 2007

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We describe a simple undergraduate lab in which students determine how the force between two magnetic dipoles depends on their separation. We consider the case where both dipoles are permanent and the case where one of the dipoles is induced by the field of the other (permanent) dipole. Agreement with theoretically expected results is quite good.
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01.50.Pa Laboratory experiments and apparatus
40.00.00 ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
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Strong Little Magnets

Michael J. Moloney

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 352 | Cited 5 times

Online Publication Date: Aug 2007

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Did you know that some strong little cylindrical magnets available in local hardware stores1 can have an effective circumferential current of 2500 A? This intriguing information can be obtained by hanging a pair of magnets at the center of a coil, as shown in Fig. 1, and measuring the oscillation frequency as a function of coil current.
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01.50.Pa Laboratory experiments and apparatus
40.00.00 ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

Noise Doppler-Shift Measurement of Airplane Speed

Ivan F. Costa and Alexandra Mocellin

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 356

Online Publication Date: Aug 2007

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See Also: Editorial Note

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This paper illustrates a new and practical experimental technique for studying the Doppler effect1–3 where the pitch variation4 of noise from a passing aircraft is used to calculate its speed.
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07.05.-t Computers in experimental physics
01.50.Pa Laboratory experiments and apparatus
01.40.J- Teacher training

Where Is the Center of Mass of Florida?

Thomas B. Greenslade, Jr.

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 359

Online Publication Date: Aug 2007

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An attention-grabbing center-of-mass demonstration uses the map of a state mounted on a sheet of heavy cardboard and cut out along the boundaries.1 The two-dimensional object is hung from a hole punched into a city near the edge, and a string with a pendulum bob attached to it passes through the center of mass. The process is repeated with a different city, and the center of mass is determined uniquely. I did this regularly with a map of the state of Ohio, and the geographic center of the state reliably came out to be the nearby village of Centerburg.
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01.50.My Demonstration experiments and apparatus
47.00.00 Fluid dynamics

Pulling a Door Open by Pushing on It

Willem H. van den Berg

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 361 | Cited 1 time

Online Publication Date: Aug 2007

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Ordinarily, opening a door by pulling on the knob or handle causes a net torque on the door, and hence an angular acceleration, about a vertical axis. However, it may be that the top or bottom of the door sticks to the door frame; this horizontal force perpendicular to the plane of the door causes a torque on the door about a horizontal axis. This latter torque is countered by an opposite torque caused by horizontal forces exerted by the hinges; the result is that the door is deformed but does not readily open. The horizontal forces between the door and the hinges can potentially tear loose the hinges. When the sticking is released, the elastic potential energy stored in the deformation of the door becomes the alternating kinetic and potential energy of an annoying oscillation.
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01.55.+b General physics
47.00.00 Fluid dynamics

Introduction to Fourier Optics

Elisha Huggins

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 364

Online Publication Date: Aug 2007

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Much like a physical prism, which displays the frequency components of a light wave, Fourier analysis can be thought of as a mathematical prism that can tell us what harmonics or frequency components are contained in a recording of a sound wave. We wrote the MacScope II program1 so that the user could not only see a plot of the harmonic amplitudes but also see the harmonic waves and how these waves add together to recreate the original sound curve.
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01.55.+b General physics
42.00.00 Optics

March of the Planets

Bruce Thompson

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 369 | Cited 1 time

Online Publication Date: Aug 2007

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The motion of the planets in their orbits can be demonstrated to students by using planetarium software programs.1 These allow time to be sped up so that the relative motions are readily observed. However, it is also valuable to have the students understand the real speed of the planets in their orbits. This paper describes an exercise that gives students a good understanding of real-time motions and then allows other questions to be asked to encourage further understanding of planetary geometry and motion.
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01.50.My Demonstration experiments and apparatus
95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations

Why Do Calculators Have Rubber Feet?

Richard M. Heavers

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 373

Online Publication Date: Aug 2007

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Our students like using the covers of their TI graphing calculators in an inquiry-based extension of a traditional exercise1 that challenges their preconceived ideas about friction. Biology major Fiona McGraw (Fig. 1) is obviously excited about the large coefficient of static friction (μs = 1.3) for the four little rubber feet on her TI calculator cover. The angle of repose of 53° is three times the value she just obtained for a wood block on the same plane. That block fits nicely inside her calculator cover. By using the string already attached to the block, the cover with the block inside can be pulled along the board at a constant speed to obtain the coefficient of kinetic friction μk for rubber on wood (Fig. 2). Results vary with the age and condition of the rubber feet. Observations with only three rubber feet on some covers help to reinforce the idea that the friction force is independent of the area of the surface in contact. (Students first study the effect of area by working with the wood block on its wide side and then on its narrow side.)
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01.40.gb Teaching methods and strategies

arXiv.org and Physics Education

Susan Ramlo

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 374

Online Publication Date: Aug 2007

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The website arXiv.org (pronounced archive) is a free online resource for full-text articles in the fields of physics, mathematics, computer science, nonlinear science, and quantitative biology that has existed for about 15 years. Available directly at http:∕∕www.arXiv.org, this e-print archive is searchable. As of Jan. 3, 2007, arXiv had open access to 401,226 e-prints in the topic areas.1 Those who sign up for an ID and password can also sign up for daily submission abstract emails for specific subject classes of arXiv, including physics education, physics and society, and history of physics. Founded and developed by Paul Ginsparg when he was at Los Alamos National Laboratory, arXiv's original name was the LANL preprint archive or xxx.lanl.gov. The location and name changed after Ginsparg moved to the physics department at Cornell University. Today, arXiv is hosted and operated by Cornell University library. Mirror sites for arXiv exist worldwide.2
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01.30.-y Physics literature and publications
01.40.Fk Research in physics education
01.75.+m Science and society

A Simple Experiment to Demonstrate the Effects of Greenhouse Gases

C. F. Keating

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 376 | Cited 2 times

Online Publication Date: Aug 2007

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The role of greenhouse gases in our atmosphere is the subject of considerable discussion and debate. Global warming is well-documented, as is the continually increasing amount of greenhouse gases that human activity puts in the air. Is there a relationship between the two? The simple experiment described in this paper provides a good demonstration of the effect of greenhouse gases in the atmosphere. This experiment lends itself well to astronomy, physics, and Earth science classes at the high school and college levels.
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01.50.Pa Laboratory experiments and apparatus
96.00.00 Solar system; planetology
82.00.00 Physical chemistry and chemical physics
32.00.00 Atomic properties and interactions with photons

Thinking About Bernoulli

Martin Kamela

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 379 | Cited 4 times

Online Publication Date: Aug 2007

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One of the most fun demonstrations in a freshman mechanics class is the levitation of a ball in a steady air stream even when the jet is directed at an angle. This and other demonstrations1 are often used to argue for the validity of Bernoulli's principle. As cautioned by some authors,2–4 however, it is important to avoid making sweeping statements such as “high speed implies lower pressure” with respect to interpreting the popular demonstrations. In this paper I present a demonstration that can be used in conjunction with the discussion of Bernoulli's principle to encourage students to consider assumptions carefully. Specifically, it shows that a correlation of high speed with lower fluid pressure is not true in general.
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01.55.+b General physics
47.00.00 Fluid dynamics

A Simple Classroom Simulation of Heat Energy Diffusing Through a Metal Bar

Mark Kinsler and Evelyn Kinzel

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 382

Online Publication Date: Aug 2007

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We present an iterative procedure that does not rely on calculus to model heat flow through a uniform bar of metal and thus avoids the use of the partial differential equation typically needed to describe heat diffusion. The procedure is based on first principles and can be done with students at the blackboard. It results in a plot that illustrates several principles of thermodynamics and can be easily implemented with a spreadsheet program on the computer.
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01.50.-i Educational aids
01.55.+b General physics
01.40.J- Teacher training
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Determining the Curie Temperature of Iron and Nickel

S. Velasco and F. L. Román

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 387

Online Publication Date: Aug 2007

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The phenomenon of ferromagnetism is well-known to high school and undergraduate students, and its physical basis is explained in most general physics textbooks.1–2 There are some elegant undergraduate experiments that investigate the ferromagnetic-paramagnetic phase transition by means of the analysis of the magnetic properties and the electrical resistance of the material above and below the transition point.3–6 However, most of the simple classroom demonstrations of this phenomenon are designed essentially for demonstrating the existence of the Curie point. In this paper we describe a rather simple demonstration experiment for determining quantitatively the Curie temperature of a ferromagnetic material.
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01.50.Pa Laboratory experiments and apparatus
05.00.00 Statistical physics, thermodynamics, and nonlinear dynamical systems
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Fermi Questions

Larry Weinstein

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 390

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.Rt Physics tournaments and contests
01.50.Kw Techniques of testing
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Paper Beats Rock

Boris Korsunsky

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 391

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.Rt Physics tournaments and contests
01.40.J- Teacher training
01.55.+b General physics
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Capacitors Made by Drawing with Graphite on Paper or Plastic

Marcos Alfredo Salami, João Bernardes da Rocha Filho, Cláudio Galli, and Rita de Cássia da Costa

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 392

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.40.J- Teacher training
01.50.My Demonstration experiments and apparatus
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Increasing the Electric Field by Squeezing Charges

Gorazd Planinšič

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 393

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
01.40.J- Teacher training
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Strategies for Adopting Interactive Engagement Methods

Mario Belloni and Anne J. Cox

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 395

Online Publication Date: Aug 2007

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Editor's note: It's very likely that interactive teaching methods may not be something you have seen modeled in your educational experiences thus far. Perhaps as you have read about effective teaching strategies, you found evidence that thoughtful interactions are essential and effective in moving students from being passive learners to actively engaged constructors of their own knowledge. To provide you with some ideas on establishing interactive engagement opportunities in your classroom, Mario Belloni and Anne Cox share suggestions from their years of experience designing quality instructional settings to foster these interactions.
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01.40.gb Teaching methods and strategies
01.40.J- Teacher training
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The Internet Physicist at http:∕∕www.vts.intute.ac.uk∕acl∕tutorial?sid=1053487&op=preview&manifestid=207&itemid=

Pat Viele

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 398

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.H- Computers in education
01.40.J- Teacher training

Online Distance Education Graduate Courses in Physics Especially for High School Physics Teachers

Dan MacIsaac

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 398

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.H- Computers in education
01.40.J- Teacher training

Online Distance Education Graduate Courses in Physics Especially for High School Physics Teachers

Dan MacIsaac

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 398

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.H- Computers in education
01.40.J- Teacher training

Online Distance Education Graduate Courses in Physics Especially for High School Physics Teachers

Dan MacIsaac

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 398

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.50.H- Computers in education
01.40.J- Teacher training
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Some Hits; Many Misses—The CBC Presentation: “Everyday Einstein”

David P. Maroun

The Physics Teacher -- September 2007 -- Volume 45, Issue 6, pp. 399

Online Publication Date: Aug 2007

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Abstract Unavailable
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01.30.Vv Book reviews
01.65.+g History of science
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