Rhett Herman

An introduction to electrical resistivity in geophysics

Physicists are finding that the skills they have learned in their training may be applied to areas beyond traditional physics topics. One such field is that of geophysics. This paper presents the electrical resistivity component of an undergraduate geophysics course at Radford University. It is taught from a physics perspective, yet the application of the theory to the real world is the overriding goal. The concepts involved in electrical resistivity studies are first discussed in a general sense, and then they are studied through the application of the relevant electromagnetic theory. Since geology majors comprise the bulk of the students in this class, the math used is only that which is typically required of geology majors. The final results are given in a form that practicing geophysicists may use in the field. A method is presented for constructing an inexpensive apparatus for measuring electrical resistivity in both a tabletop laboratory setting and in the field. This apparatus is truly “plug and pl...

As simple as possible

An extremely simple method for building a basic loudspeaker is presented. This loudspeaker may be built in just a few minutes from a bare minimum of materials.

Renormalization of the charged scalar field in curved space.

The DeWitt-Schwinger proper time point-splitting procedure is applied to a massive complex scalar field with an arbitrary curvature coupling interacting with a classical electromagnetic field in a general curved spacetime. The scalar field current is found to have a linear divergence. The presence of the external background gauge field is found to modify the stress-energy tensor results of Christensen for the neutral scalar field by adding terms of the form ({ital eF}){sup 2} to the logarithmic counterterms. These results are shown to be expected from an analysis of the degree of divergence of scalar quantum electrodynamics. {copyright} {ital 1996 The American Physical Society.}

Spreadsheet physics: Examples in meteorology and planetary science

By utilizing the iterative capabilities of spreadsheets, students who do not have a programming background may obtain numerical solutions to complex equations. This paper discusses two examples of spreadsheet programming. One models the structure of a planet using a set of ordinary differential equations depending on the radius of the planet. The other involves coupled partial differential equations in a model of a planetary atmosphere. The results of the planetary models are compared to the values for Earth and Neptune. The results of the atmospheric model are compared to values for Earth’s atmosphere.

Let’s Catch a (Heat) Wave

Two students in a recent thermodynamics/statistical mechanics course needed to complete a course-related project to receive honors credit for the class. Such courses are typically theoretical, without an accompanying laboratory, although there are existing related hands-on exercises. The choice of the project was influenced by one student’s desire to become a mechanical engineer after graduating while the other wanted a project that was “fun” without “just doing more calculations.” The choice of this particular project was further refined by the future engineer’s interest in the thermodynamics of car engines.

Simple Ways to Make Real Capacitors

Many of us have grabbed two pieces of aluminum foil and a paper towel, quickly sandwiched them together, and exclaimed in lecture, “Look! Its easy to make a capacitor!” Then we move on from there, calculating things such as capacitances with various dielectrics or plate sizes, the capacitance of capacitor networks, RC circuits, etc. We typically do these calculations with capacitance values that are far removed from what we just created in our quick demonstration of a capacitor. Students might justifiably question whether the capacitor that we blithely made has any relation to the values that we are using in our calculations. It may be useful to investigate the quality of such handmade capacitors so that our students get a more intuitive feel for these ubiquitous electrical components.