Table of contents

Volume 46

Number 4, July 2011

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News

365

Conference: Serbia hosts teachers' seminar Resources: Teachers TV website closes for business Festival: Science takes to the stage in Denmark Research: How noise affects learning in secondary schools CERN: CERN visit inspires new teaching ideas Education: PLS aims to improve perception of science for school students Conference: Scientix conference discusses challenges in science education

Frontline

Corrigendum

Features

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In this article we describe an experimental learning path about electromagnetic induction which uses an Atwood machine where one of the two hanging bodies is a cylindrical magnet falling through a plexiglass guide, surrounded either by a coil or by a copper pipe. The first configuration (magnet falling across a coil) allows students to quantitatively study the Faraday–Neumann–Lenz law, while the second configuration (falling through a copper pipe) permits learners to investigate the complex phenomena of induction by quantifying the amount of electric power dissipated through the pipe as a result of Foucault eddy currents, when the magnet travels through the pipe. The magnet's fall acceleration can be set by adjusting the counterweight of the Atwood machine so that both the kinematic quantities associated with it and the electromotive force induced within the coil are continuously and quantitatively monitored (respectively, by a common personal computer (PC) equipped with a webcam and by freely available software that makes it possible to use the audio card to convert the PC into an oscilloscope). Measurements carried out when the various experimental parameters are changed provide a useful framework for a thorough understanding and clarification of the conceptual nodes related to electromagnetic induction. The proposed learning path is under evaluation in various high schools participating in the project 'Lauree Scientifiche' promoted by the Italian Department of Education.

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To diversify the measurement techniques of Avogadro's number in physics teaching, I propose a simple acoustic method for the experimental determination of Avogadro's number based only on the measurement of the speed of sound in metals, provided that their Debye temperatures are known.

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In this article we make some significant remarks on the experimental study of the absorption of gamma radiation passing through matter. These remarks have to do with the seemingly unexpected trend of the measured intensity of radiation versus the thickness of the absorber, which puzzles students and its explanation eludes many laboratory assistants.

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The field of extrasolar planets is still, in comparison with other astrophysical topics, in its infancy. There have been about 300 or so extrasolar planets detected and their detection has been accomplished by various different techniques. Here we present a simple laboratory experiment to show how planets are detected using the transit technique. Following the simple analysis procedure describe we are able to determine the planetary radius to be 1.27 ± 0.20RJ which, within errors, agrees with the established value of 1.32 ± 0.25RJ.

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Imaging of three-dimensional objects by lenses and mirrors is sometimes poorly indicated in textbooks and can be incorrectly drawn. We stress a need to clarify the concept of longitudinal magnification, with simulated images illustrating distortions introduced along the optical axis. We consider all possible positions of the object for both a convergent and a divergent lens, producing real and virtual images. We also discuss spherical mirrors, elementary telescopes and microscopes.

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The following article is Free article

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Misconceptions of siphon action include assumptions that intermolecular attractions play a key role and that siphons will operate in a vacuum. These are belied by the siphoning of gaseous carbon dioxide and behaviour of siphons under reduced pressure. These procedures are suitable for classroom demonstrations. The principles of siphon action are summarized.

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Physics is essential for students who want to succeed in science and engineering. Excitement and interest in the content matter contribute to enhancing this success. We have developed a laboratory experiment that takes advantage of microwave ovens to demonstrate important physical concepts and increase interest in physics. This experiment investigates leaked electromagnetic radiation from microwave ovens. We compare the data that are obtained to national standards in order to relate the fields of physics, health and engineering. The experiment is designed to provide for added enquiry and stimulation of thought-provoking questions.

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A key question in physics education is the effectiveness of the teaching methods. A curriculum that has been investigated at the University of Central Florida (UCF) over the last two years is the use of particular elements of The Physics Suite. Select sections of the introductory physics classes at UCF have made use of Interactive Lecture Demonstrations as part of the lecture component of the class. The laboratory component of the class has implemented the RealTime Physics curriculum, again in select sections. The remaining sections have continued with the teaching methods traditionally used. Using pre- and post-semester concept inventory tests, a student survey, student interviews, and a standard for successful completion of the course, the preliminary data indicate improved student learning.

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A very low-cost, easy-to-make stopwatch is presented to support various experiments in mechanics. The high-resolution stopwatch is based on two photodetectors connected directly to the microphone input of a sound card. Dedicated free open-source software has been developed and made available to download. The efficiency is demonstrated by a free fall experiment.

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Sir Nevil Maskelyne is remembered by many as the main rival to clockmaker John Harrison in the famous Longitude affair of the 18th century. However, his contributions to science go well beyond this often misreported drama; three of his many observations and developments are considered here in the year marking the 200th anniversary of his death.

437

What follows is an alternative to the standard tuning fork and quarter-wave tube speed of sound experiment. Rather than adjusting the water level in a glass or plastic tube to vary the length of an air column, a set of resonance tubes of different lengths is used. The experiment still demonstrates the principles of standing waves in air columns and can also be used to study end-correction as well as determining the speed of sound in air.

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An experiment to verify the Doppler effect of sound waves is described. An ultrasonic source is mounted at the end of a simple pendulum. As the pendulum swings, the rapid change of frequency can be recorded by a stationary receiver using a simple frequency-to-voltage converter. The experimental results are in close agreement with the Doppler formula.

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Mainly used in the 1960s, bubble chambers played a major role in particle physics. Now replaced with modern electronic detectors, we believe they remain an important didactic tool to introduce particle physics as they provide visual, appealing and insightful pictures. Sadly, this rare type of detector is mostly accessible through open-door events only. To overcome this drawback, we have developed a realistic computer-based simulator to replicate the actual equipment. Using this software, students and instructors are able to obtain randomly created computer-simulated images comparable to real-life ones. We have successfully used this software in our mechanics, electromagnetism and modern physics courses to illustrate the effect of a magnetic field on charged particles, to exemplify relativistic mechanics and to discuss the conservation of energy, momentum and quantum numbers in particle collisions. It also provides original examples for students to practise their ability to identify the particles involved, thereby gaining a better understanding of the underlying physical laws. The software is available as a free download.

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We propose a new format of scientific entertainment in which customers of a restaurant can order small experiments in place of entrées and drinks.

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This article describes a few simple experiments that are worthwhile for slow motion recording and analysis either because of interesting phenomena that can be seen only when slowed down significantly or because of the ability to do precise time measurements. The experiments described in this article are quite commonly done in Czech schools.

All high-speed videos were taken using a Casio Exilim EX-F1 camera that can produce slow motion videos recorded at a rate of 1200 FPS (frames per second). When played back at the standard rate of 30 FPS, the motion is slowed down 40 times. The videos described in this article are accessible via http://bit.ly/slow-motion-physics.

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With the development of LabVIEW™ Education Edition schools can now provide experience of using this widely used software. Here, a few of the many applications that students aged around 11 years and over could develop are outlined in the resulting front panel screen displays and block diagrams showing the associated graphical programmes, plus a couple which are more complex provided for direct use.

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Articulated bodies with an internal energy source require to be coupled to an external mass in order to accelerate themselves but the typical text book assertion that the net force is provided by the external mass is not correct. Arguments are presented demonstrating that the assertion is incorrect and reasons are suggested for the persistence of this mistake.

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A selection of hands-on experiments from different fields of physics, which happen too fast for the eye or video cameras to properly observe and analyse the phenomena, is presented. They are recorded and analysed using modern high speed cameras. Two types of cameras were used: the first were rather inexpensive consumer products such as Casio Exilim cameras operating at frame rates of up to 1200 Hz for reduced image sizes and the second were higher quality research cameras, which allow much higher frame rates at larger image sizes. In this first article, examples are presented from exploding balloons demonstrating retardation in mechanics, karate hits, deformations associated with the bouncing of balls, strange trajectories of 'superballs' as well as the breaking of spaghetti.

Reviews

487

WE RECOMMEND

Fun Fly Stick Science Kit Fun fly stick introduces electrostatics to youngsters

Special Relativity Text makes a useful addition to the study of relativity as an undergraduate

LabVIEWTM 2009 Education Edition LabVIEW sets industry standard for gathering and analysing data, signal processing, instrumentation design and control, and automation and robotics

Edison and Ford Winter Estates Thomas Edison's home is open to the public

The Computer History Museum Take a walk through technology history at this computer museum

WORTH A LOOK

Fast Car Physics Book races through physics

Beautiful Invisible The main subject of this book is theoretical physics

Quantum Theory Cannot Hurt You A guide to physics on the large and small scale

Chaos: The Science of Predictable Random Motion Book explores the mathematics behind chaotic behaviour

Seven Wonders of the Universe A textual trip through the wonderful universe

HANDLE WITH CARE

Marie Curie: A Biography Book fails to capture Curie's science

WEB WATCH Web clips to liven up science lessons

Letters

End Results

501

What Happens Next?: Effect of plasticine on falling rodsDavid Featonby

Insights and Conundrums: de Broglie's wavelength has many applications in the study of gasesRick Marshall

Signing Off: The life and work of Marie CurieDavid Smith