The study of electricity and magnetism is fundamental to all first-year physics courses. Developing simple electricity laboratory experiences that are open ended and inquiry based can be difficult. We wished to create a lab experiment where the students have some control over the experimental design, data analysis is required, and students…

Edwin Herbert Hall (1855-1938), discoverer of the Hall effect, was one of the first winners of the AAPT Oersted Medal for his contributions to the teaching of physics. While Hall's role in establishing laboratory work in high schools is widely acknowledged, his position as chair of the physics section of the Committee on College Entrance…

In the popular press, diagrams showing the evolution of the universe begin with a great jump in size labeled "inflation." Can we explain the basic ideas behind inflation to our students who have taken our introductory physics course? Probably not. In our standard introductory physics courses, even those with special relativity, something…

The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…

A major consequence of special relativity, expressed in the relation E[subscript 0] = mc[superscript 2], is that the total energy content of an object at rest, including its thermal motion and binding energy among its constituents, is a measure of its inertia, i.e., its mass. This relation was first stated by Einstein. He showed that, in order to…

A goldfish isn't always visible inside its fishbowl. If the fish gets sufficiently close to the bowl glass, it will disappear for certain angles of observation. In a recent paper in this journal, Zhu and Shi explained the effect in terms of total internal reflection. We show in what follows that the phenomenon involves some richer optics: a…

While on a vacation flight from Hawaii to California, I observed sunset occurring on clouds far below. The view triggered a vague memory about a fun article 1 published more than three decades earlier on the topic of "Doubling Your Sunsets." Simple observations from my flight made it possible to compute the Earth's radius.

This is the fourth paper in a series of four. The first paper in the series, "Vacuum Energy and Inflation: 1. A Liter of Vacuum Energy" [EJ1024183] discusses an example of vacuum energy. Vacuum energy is explained as an energy with a negative pressure whose energy density remains constant in an expanding space. Paper 2, "Vacuum…

The atmospheric recycling of water is a very important phenomenon on the globe because it not only refreshes the water but it also redistributes it over land and oceans/rivers/lakes throughout the globe. This is made possible by the solar energy intercepted by the Earth. The half of the globe facing the Sun, on the average, intercepts 1.74 ×…

A rattleback is a well-known physics toy that has a preferred direction of rotation. If it is spun about a vertical axis in the "wrong" direction, it will slow down, start rocking from end to end, and then spin in the opposite (i.e. preferred) direction. Many articles have been written about rattlebacks. Some are highly mathematical and…

The leaf electroscope is a common piece of demonstration equipment found in many high school and introductory college physics laboratories. Its simplicity allows a compelling demonstration of electrostatic forces, and its versatility makes it useful in the demonstration of a number of physical phenomena. The electroscope has a long history; a…

Enrollments in physics courses at two-year colleges About 176,000 students were enrolled in various physics courses on two-year college (TYC) campuses during the 2011-12 academic year. This represents a 60% increase in enrollments since the 1995-96 academic year. Enrollments in conceptual physics courses more than doubled during this period, going…

I have used many ploys to start a course in introductory physics, but one of the more interesting ones was to spend 20 minutes describing some of the curves and shapes that we would encounter in our year together. The students saw parabolas, catenaries, hyperbolas, cycloids, circles, ellipses, and helices, and were shown examples, either live or…

The ordinary 12-oz beverage cans in the figures below are not held up with any props or glue. The bottom of such cans is stepped at its circumference for better stacking. When this kind of can is tilted, as shown in Fig. 1, the outside corners of the step touch the surface beneath, providing an effective contact about 1 cm wide. Because the…

The equation describing the magnetic field due to a single, nonrelativistic charged particle moving at constant velocity is often referred to as the "Biot-Savart law for a point charge." Introductory calculus-based physics books usually state this law without proof. Advanced texts often present it either without proof or as a special…