What if energy flowed from cold to hot regions? How would thermodynamics be different? We examine such an imagined cold-to-hot world, abbreviated here as a C2H world, and show that the unfamiliar direction of energy flow implies that two thermally interacting objects at different temperatures will not equilibrate. We find that there is no…

Breathing is something we all do, usually without thinking about it. But when viewed through the lens of physics, respiration becomes an example of elementary thermodynamics. As shown here, the lungs can be modeled as a two-stroke heat engine. Breathing thereby provides a novel physics application for life science students, demonstrating the…

An attempt to calibrate a conventional oven led to making a measurement of a thermophysical property of water using items found in the author's home. Specifically, the ratio of the energy required to heat water from the melting point to boiling to the energy required to completely boil away the water is found to be 5.7. This may be compared to the…

Project-based learning has been shown to be an effective pedagogical strategy that motivates students and thus promotes learning. In this article we describe a project-based unit centered on the physics of solar cookers (Fig. 1 and 3). Our goal was to elevate the solar cooker from a summer camp activity to a college-level project that could be…

The possibility of negative temperatures on the Kelvin scale is intriguing and confusing simultaneously. This is because students are used to thinking of temperature as a measure of the internal energy of a system. While this concept is good for many systems, it does not work for all systems. Nuclear and electron spin systems, along with lasers…

While entropy is often described as "disorder," it is better thought of as a measure of how spread out energy is within a system. To illustrate this interpretation of entropy to introductory college or high school students, several activities have been created. Students first study the relationship between microstates and macrostates to…

The ability of our society to make informed energy-usage decisions in the future depends partly on current science and engineering students retaining a deep understanding of the thermodynamics of heat engines. Teacher imaginations and equipment budgets can both be taxed in the effort to engage students in hands-on heat engine activities. The…

MAUVE (magnitude, answer, units, variables, and equations) is a framework and rubric to help students and teachers through the process of clearly solving and assessing solutions to introductory physics problems. Success in introductory physics often derives from an understanding of units, a command over dimensional analysis, and good bookkeeping.…

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…

The literature has revealed that many students encounter substantial difficulties in applying the first law of thermodynamics. For example, university students sometimes fail to recognize that heat and work are independent means of energy transfer. When discussing adiabatic processes for an ideal gas, few students can correctly refer to the…

Energy is a critical concept that is used in analyzing physical phenomena and is often an essential starting point in physics problem-solving. It is a global concept that appears throughout the physics curriculum in mechanics, thermodynamics, electromagnetism, and modern physics. Energy is also at the heart of descriptions of processes in biology,…

Briefly mentions pre-19th century ideas and discusses the contributions of Mohr, Seguin, Mayer, Grove, Colding, Joule and Helmholtz and the controversies regarding priority including Tyndall's involvement in one of them. Mentions the tension between philosophical and practical modes of thought in 19th century science. Includes portraits. (GH)

Describes the working of the Adiabatic Gas Law Apparatus, a useful tool for measuring the pressure, temperature, and volume of a variety of gases undergoing compressions and expansions. Describes the adaptation of this apparatus to perform isothermal measurements and discusses the theory behind the adiabatic and isothermal processes. (JRH)

Studies the practicality of water-filled flat-plate solar collectors. An estimate of solar energy gathering abilities and applications in heating of homes are considered. (CP)

Demonstrates misconceptions of the meaning of temperature based on classical kinetic energy. Discusses some misconceptions about negative temperatures and the effect of compression. (YP)