A solid understanding of the difference in the electric properties of conductors and insulators is key to making sense of the rest of the material in introductory electricity and magnetism. When asked “What is a conductor (or insulator)?” many introductory physics students can easily tell you: “A metal is a conductor,” and/ or they recite the definition. However, when asked “How do you know or how do you convince a friend in your physics class that electric charges can move freely in a (electrical) conductor?” most students have great difficulty answering the question.1 Don't be surprised if they just tell you that is what the textbook or physics professor says. This paper will illustrate a simple demonstration using an aluminum pie pan and foam board that helps students develop a solid understanding of the fundamental difference between a conductor and insulator. Table I shows detailed information on how to prepare the demonstration. Like any other electrostatics experiment, this demonstration requires low humidity in air. As a matter of fact, it is very difficult to perform the experiment successfully when a classroom is full of students.2 To help teachers do this, a QuickTime movie of the demonstration is made and can be downloaded from http://www.csuchico.edu/~xzou.

Topics
Electrical properties and parameters, Electrostatics, Chemical elements, Educational aids, Teaching
1.
X. Zou, K. Harper, E. Etkina, and A. Van Heuvelen, “The epistemological beliefs and thinking patterns of students in the investigative science learning environment,” AAPT Summer Meeting, Boise, ID, Aug. 2002.
2.
To help perform this demonstration successfully in a classroom, the instructor may use a dehumidifier to dry the room.
3.
R. W. Chabay and B. A. Sherwood, Matter & Interactions, Vol. II (Wiley, New York, 2002), pp. 461–466.
4.
A.4E. Lawson, Science Teaching and the Development of Thinking (Wadsworth Publishing Co., Belmont, CA, 1995), pp. 134–139.
5.
E. Etkina and A. Van Heuvelen, “Investigative science learning environment: Using the processes of science and cognitive strategies to learn physics,” in Proceedings of the Physics Education Research Conference (Rochester, NY, 2001), pp. 17–21.
6.
X. Zou, “Experimental designs in the introductory physics laboratory,” Northern California/Nevada Section AAPT Meeting, San Francisco, CA, Nov. 2002.
7.
X. Zou, “How students justify their knowledge in the investigative science learning environment,” in Proceedings of the National Conference of Physics Education Research Conference (Madison, WI, 2003), pp. 105–108.
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© 2005 American Association of Physics Teachers.
2005
American Association of Physics Teachers
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