At 11:55 AM 3/7/2002 -0500, James R. Frysinger wrote: > I cannot sufficiently express how frustratingly difficult it is to >teach students that the concept of power crosses into many areas: >electrical, mechanical, thermal, etc. For American students, an obvious >source of confusion is the plethora of units that are commonly used, as >you have put it above, Duncan. Indeed, they sometimes try to tell me >that "these powers are different" on the basis of the differing units. I >wonder how my experience compares to that of instructors in physics >classrooms in metricated countries.
My experience teaching people, including some who do not even have high school diplomas, isn't quite this bad. I use two different methods that seem to help. First, to teach the difference between power and energy, at the start of a class I put out two sets of four AA batteries, one running a small penlight (wired in parallel), the other running a larger spotlight (wired in series). By the end of class the spotlight is dead, while the penlight goes for several hours. Everyone inherently understands that the two sets of batteries contain the same energy, so it is relatively easy to grasp the power being different. As to the different types of power (and energy), I give them (rounded) conversion factors for a variety of units, and have them figure out how long a Twinkie will "power" a car, or how long a battery would "feed" a human, or how much the natural gas a house uses in a month would if it were peanut butter. Using such crazy comparisons helps them grasp that energy is energy in whatever form. Jim Elwell
