Robert A. Morse

Electrostatics with Computer-Interfaced Charge Sensors

Computer interfaced electrostatic charge sensors1,2 allow both qualitative and quantitative measurements of electrostatic charge but are quite sensitive to charges accumulating on modern synthetic materials. They need to be used with care so that students can correctly interpret their measurements. This paper describes the operation of the sensors, precautions for using them, and suggestions for experiments with sample readings.3

Fan Unit Physics

A lightweight motor-driven propeller mounted on a low-friction cart provides a nearly constant thrust over a moderate range of velocities and can be a powerful pedagogical tool for investigating force and motion. A variety of homemade and commercial versions are now available. This article revisits and extends the topic of fan unit use described earlier.1 It looks at the rationale for use of fan units, gives examples of teaching ideas, and describes construction of two homemade versions of fan units.

Inexpensive Dramatic Pneumatic Lift

Various experiments and demonstrations relate air pressure and air pressure difference to force and area. Carpenter and Minnix describe a large-scale pneumatic lift in which a person sitting on a board atop a plastic garbage bag is lifted when the bag is connected to the exhaustport of a vacuum cleaner, which easily lifts the person. This article describes the construction and use of an inexpensive hand-held pneumatic lift to demonstrate the same principle.

Simple Pencil-and-Paper Notation for Representing Electrical Charge States

In Benjamin Franklin’s one fluid theory of electrification, ordinary unelectrified matter consisted of a matrix of matter suffused with a certain amount of “electrical fluid.” Electrical effects were due to an excess or deficit of electrical fluid, hence the terms positive and negative. Before the development of a modern view of the atom, diagrams showing charged objects would simply have “+” or “–” signs to indicate the charged state. As physicists we know how to interpret these diagrams and understand what they are telling us about the underlying atomic model of charging. However, novice students may not readily make the connection between the atomic model, in which a charged solid object either gains or loses electrons but does not gain or lose positive charges. Furthermore, when isolated objects become charged, the total number of electrons must be accounted for as charge is a conserved quantity. To really understand the changes that occur in charging by contact, conduction, or induction, it is useful...

Get Real! — Physically Reasonable Values for Teaching Electrostatics

Students get a sense of realistic values for physical situations from texts, but more importantly from solving problems. Therefore, problems should use realistic values for quantities to provide needed practice. Unfortunately, some problems on tests and in textbooks do not use realistic values. Physical situations in electrostatics seem to be particularly problematic.

Commedia Dell'Arte as a Metaphor for the Art of Teaching.

With my background in acting, stagecraft, and some knowledge of theatre history from high school and college, it was natural for me as a novice teacher to think about theatre as a metaphor for teaching. In this article I will discuss how over my career I conceived of teaching in terms of theatrical metaphors, and make a comparison with a common metaphor of teaching as coaching.

Galvanize Your Class! Build a Battery of Students

An inexpensive and simple class participation demonstration uses students, short lengths of metal pipe, and an inexpensive digital voltmeter to make a battery of students. Data taken illustrate the combination of emfs in series and parallel. This apparatus was awarded second place and a low‐cost award in the 2007 AAPT Apparatus Competition.

Different Representations of Physics or Hail Poetry! — Thou heaven-born maid, thou gildest e'en the physics teacher's trade! (stolen from W. S. Gilbert)

Robert Morse, physics teacher at St. Albans School in Washington, D.C., has taught physics in public and private schools for 37 years. His website on Ben Franklin and Electrostatics was recently reviewed in the June 2006 issue of Natural History Magazine. A previous foray into poetry, “The Pool Table Physics Lab Rap,” is one of the pieces on the Physics Pholk Songs CD, part of the Activity-Based Physics project.