Highlights of 2016

In this paper we present a novel way to demonstrate the Hall effect and study some of its main properties using basic materials and easily obtainable measuring devices.

Under certain conditions a body of hot liquid may cool faster and freeze before a body of colder liquid, a phenomenon known as the Mpemba Effect. An initial difference in temperature of 3.2 °C enabled warmer water to reach 0 °C in 14% less time than colder water. Convection currents in the liquid generate a temperature gradient that causes more rapid heat loss by surface radiation and evaporation than obtains for uniform temperature. This more rapid cooling enables the initially warmer liquid to overtake the cooler liquid, reaching 0 °C earlier and freezing first.

Liquid cooling under natural convection follows a five-fourths power law (temperature of liquid $T$, temperature of surroundings ${{T}_{a}}$, cooling constant $k$): $\frac{\text{d}T}{\text{d}t}=k{{\left(T-{{T}_{a}}\right)}^{\frac{5}{4}}}$. In this investigation we found that with evaporation this becomes a four-thirds power law:

$$\begin{eqnarray}&&\frac{\text{d}T}{\text{d}t}=k{{\left(T-{{T}_{a}}\right)}^{\frac{4}{3}}}\end{eqnarray}$$

In 1974, the British physicist Stephen Hawking discovered that black holes have a characteristic temperature and are therefore capable of emitting radiation. Given the scientific importance of this discovery, there is a profuse literature on the subject. Nevertheless, the available literature ends up being either too simple, which does not convey the true physical significance of the issue, or too technical, which excludes an ample segment of the audience interested in science, such as physics teachers and their students. The present article seeks to remedy this shortcoming. It develops a simple and plausible argument that provides insight into the fundamental aspects of Hawking's discovery, which leads to an approximate equation for the so-called Hawking temperature. The exposition is mainly intended for physics teachers and their students, and it only requires elementary algebra, as well as basic notions of Newtonian mechanics and quantum theory.

If a compact disc (CD) is placed in front of a plane mirror, its image displays different colours from the ones observed in the real CD. This fact occurs because a CD surface is a diffraction grating which disperses the incident wavelengths. As the object and its image are seen from different viewing angles, the observed colours are not the same, so the image cannot be considered symmetrical to the object. A theoretical discussion on the topic and a simple experimental activity, adequate to secondary school, are presented.

Gravity racing can be studied using numerical solutions to the equations of motion derived from Newton's second law. This allows students to explore the physics of gravity racing and to understand how design and course selection influences vehicle speed. Using Euler's method, we have developed a spreadsheet application that can be used to predict the speed of a gravity powered vehicle. The application includes the effects of air and rolling resistance. Examples of the use of the application for designing a gravity racer are presented and discussed. Predicted speeds are compared to the results of an official world record attempt.

The thought experiment 'Schrödinger's cat' exposes fundamental dilemmas in how we interpret quantum physics, and has a potential for deepening students' understanding of this part of modern physics, including its philosophical consequences. In this paper we report results from the project ReleQuant on how Norwegian physics students in upper secondary schools interpret the thought experiment. The analysis resulted in nine categories, and we discuss how these relate to interpretations made by physicists, in particular the concept of superposition. Even if students' responses in many cases can be related to interpretations that make sense in physics, we conclude that lack of knowledge about the purpose and the historical context of the thought experiment limits students understanding of the physics content. Exploring the thought experiment from a historical perspective might deepen student understanding of key concepts in quantum physics as well as of how physics develops.

Modern skyscrapers are not built using traditional bricks, despite the fact that they would be strong enough to withstand very large compressive forces.

A new simple arrangement how to demonstrate diamagnetic levitation is presented. It uses pencil lead levitating in a track built from neodymium magnets. This arrangement can also be used as a classroom experiment.

The ability to categorize problems based upon underlying principles, rather than contexts, is considered a hallmark of expertise in physics problem solving. With inspiration from a classic study by Chi, Feltovich, and Glaser, we compared the categorization of 25 introductory mechanics problems based upon similarity of solution by students in large calculus-based introductory courses with physics faculty and PhD students. Here, we summarize the study and suggest that a categorization task, especially when conducted with students working with peers in small groups, can be an effective pedagogical tool to help students in introductory physics courses learn to discern the underlying similarity between problems with diverse contexts but the same underlying physics principles.

The original paper

The papers 'Randomness at the root of all things', 1 (Ogborn et al 2003 Phys. Educ. 38 391) and 2 (Ogborn et al 2003 Phys. Educ. 38 398) were written by Jon Ogborn, Mick Brown and Simon Collins in 2003.

1 in 12 males suffer from some form of colour vision deficiency (CVD) which in the present colour dominated world of education presentation can be a severe disadvantage. Although aware of 'colourblindness' most teachers make little or no adjustment for these pupils for whom tasks may be more difficult. This article examines colour vision deficiency and looks at ways in which we can help the many students who have this problem.

The paper 'Computer simulation of electric field lines' (Kirkup 1985 Phys. Educ. 20 142) appeared in 1985 and contains details of a BBC computer program that does exactly what the title says.

A cordless mouse with an added reed switch is used as a wireless data logger to record every time the wheel of a trolley completes a revolution. The limitations of the system in terms of maximum clicking rate and spatial resolution are considered and data obtained from the descent of a trolley down a ramp at various different angles is analysed in different ways. The data is analysed to obtain initial accelerations (down the ramp) and subsequent decelerations (on the flat), as well as maximum velocities, and these results are used to compare the actual performance of the trolley (with friction) with the theoretical expectation. An agreement of better than 2% on the value of gravity is obtained. Encouraging agreement on frictional forces (and accelerations) is also obtained by considering the maximum kinetic energies reached at the bottom of the ramp. This paper includes the free provision of custom software to record the time history of the clicking of a mouse.

The clear introduction of basic concepts and definitions is crucial for teaching any topic in physics. I have always found it difficult to teach fields. While searching for better explanations I hit on an approach of reading foundational texts and electromagnetic textbooks in ten year lots, ranging from 1840 to the present. By combining this with modern techniques of textual interpretation I attempt to clarify three introductory concepts: how the field is defined; the principle of superposition and the role of the electrostatic field in a circuit.

In this paper we examine the phenomena that arise around an electrically charged sharp metal spike and present numerous experiments that can be used in the teaching of electrostatics. The experiments are quite spectacular and attention-grabbing while being relatively simple and easy to perform in any decently supplied physics education laboratory that is equipped with an electrostatic machine (like a Wimshurst machine).

Rotating swing rides can be found in many amusement parks, in many different versions. The 'wave swinger' ride, which introduces a wave motion by tilting the roof, is among the classical amusement rides that are found in many different parks, in different sizes, from a number of different makes and names, and varying thematization. The 'StarFlyer' is a more recent version, adding the thrill of lifting the riders 60 m or more over the ground. These rotating swing rides involve beautiful physics, often surprising, but easily observed, when brought to attention. The rides can be used for student worksheet tasks and assignments of different degrees of difficulty, across many math and physics topics. This paper presents a number of variations of student tasks relating to the theme of rotating swing rides.

In the context of the recent re-start of CERN's Large Hadron Collider (LHC) and the challenge presented by unidentified falling objects (UFOs), we seek to facilitate the introduction of high energy physics in the classroom. Therefore, this paper provides an overview of the LHC and its operation, highlighting existing education resources, and linking principal components of the LHC to topics in physics curricula.

The concept of reactance in AC electrical circuits is often non-intuitive and difficult for students to grasp. In order to address this lack of conceptual understanding, classroom exercises compare the predicted resistance of a power tool, based on electrical specifications, to measured resistance. Once students discover that measured resistance is smaller than expected, they are asked to explain these observations using previously studied principles of magnetic induction. Exercises also introduce the notion of inductive reactance and impedance in AC circuits and, ultimately, determine self-inductance of the motor windings within the power tool.

In this paper, I take a sociological approach to understanding the under-representation of gender and physics. I argue that gender is something we do not something that we are. Thus, every aspect of our behaviour, including our engagement (or not) with physics becomes part of our performance of gender. I then use a brief historical analysis and an example from popular culture to show how physics is culturally aligned with masculinity. The impact is that the subject feels more 'natural' for men than for women. I end with some of the implications of this for those who want to make physics more accessible to girls and women.

(EDITORS NOTE: This paper was given at the Improving Gender Balance (IGB) conference in Cambridge, UK, in March 2015, organised by the Institute of Physics. This conference was for schools and their supporters who were part of the IGB strand of the Stimulating Physics Network, funded by the Department for Education. It aimed to summarise some of the sociological perspectives on girls and physics for the benefit of the teachers attending the conference. We feel that it may be a useful summary for those teachers of physics who are unfamiliar with sociological approaches to gender and the classroom.)