This paper presents a comparative study of the thermal efficiencies of mechanical heat engines by using a graphical approach based on the pressure-volume ("P-V") diagram. Three types of idealized thermodynamic cycles--the Otto, the Diesel and the Brayton--are compared in pairs. Given the same temperature range within which the engines…

In this paper, an in-class activity concerned with real image formation by a converging lens in the context of accommodation in human eyes is described. In the first part of the activity, students are encouraged to experience the accommodation of their eyes in a prescribed way using simple materials. In the second part, the accommodation function…

Here is a way to show a sound wave travelling through air in real time. The method employs a set of low-cost microphone--LED units and demonstrates the movement of a pulse of sound as it lights up LEDs along a long (100-200 m) distance across a field. (Contains 4 figures.)

The phenomenon of interference has great importance in understanding the wave properties of light. Here, we demonstrate the effect of a moving reference frame on an interference pattern by building a simple Sagnac interferometer, without the burden of using optical fibres. A generalized theoretical derivation for an arbitrarily shaped…

The maximum power theorem is a useful extension to work on EMF and internal resistance at school level. Furthermore, a very simple physical collision model can be used to show equivalent mathematical patterns to those found with the maximum power theorem and to emphasize fundamental links to ideas of impedance matching. (Contains 2 tables and 6…

We describe recent experiments at CERN in which antihydrogen, an atom made entirely of antimatter, has been held in a magnetic minimum neutral atom trap and subjected to microwave radiation to induce a resonant quantum transition in the anti-atom. We discuss how this, the first experiment to observe an interaction between an antihydrogen atom and…

Assuming a constant mass decrease per unit surface and unit time we provide a very simplistic model for the dissolution process of spherical candies. The aim is to investigate the quantitative behaviour of the dissolution process throughout the act of eating the candy. In our model we do not take any microscopic mechanism of the dissolution…

Studies have shown that standard lectures and instructional laboratory experiments are not effective at teaching interference and diffraction. In response, the author created an interactive computer program that simulates interference and diffraction effects using the finite difference time domain method. The software allows students to easily…

This experimental activity aims to visualize the variations in the tension force on a rope with a mass attached to it in horizontal and vertical circular motion. The results facilitate comprehension of the effect of the direction of the radial force in changing the magnitude of the tension force. (Contains 10 figures.)

We use the context of astroparticle physics to introduce several fundamental concepts in physics and astrophysics. An activity has been developed using inexpensive materials that allows the reconstruction of the impact point and arrival direction of a cosmic ray particle measured by the Pierre Auger Observatory. The activity includes the…

The familiar bell-jar demonstration, commonly used to show that sound cannot travel in a vacuum, is revisited in this study. It is suggested that by emphasizing the different media present in this set-up, sound propagation in near-vacuum conditions can be made possible. In this way, the concept of sound propagation in this set-up can be examined…

We present a number of simple demonstration experiments recorded with high-speed cameras in the fields of gas dynamics and thermal physics. The experiments feature relatively slow combustion processes of pure hydrogen as well as fast reactions involving oxy-hydrogen in a stoichiometric mixture. (Contains 4 figures.)

An active learning sequence based on the predict-observe-explain teaching strategy is applied to a lesson on buoyant force. The results obtained clearly justify the use of this teaching method and suggest devising a series of activities to enable more effective removal of students' commonly held alternative conceptions regarding floating and…

Research has shown that students have difficulty understanding the underlying process of the photoelectric effect. Thus, this study sought to utilize an inductively situated lesson for teaching the photoelectric effect, hypothesizing that this type of enquiry would help learners delve deeper into the principles of the phenomenon and provide a…

We have developed an exciting non-traditional experiment for our introductory physics laboratories to help students to understand the principle of conservation of angular momentum. We used electric toy cars moving along a long rotating rod. As the cars move towards the centre of the rod, the angular velocity of this system increases.…