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Main Curriculum Tie:
Background For Teachers:
There are several kinds of electrostatic generators, including an electrophorus, which is the simplest to set up and use in a classroom. Rubbing the Styrofoam™ plate with the woolen cloth causes the Styrofoam™ to become charged with electrons (- charge) at the surface. Since Styrofoam™ is an insulator, it cannot transfer its electrons to another material. When the aluminum pie pan is placed on the Styrofoam™, a charge is produced in the pie pan. Since aluminum is a good conductor, the negative charge at the surface of the Styrofoam™ plate causes the electrons in the pie pan to move away from the Styrofoam™ up to the edge of the pie pan. As your finger comes close to the edge of the pie pan as it sits on the Styrofoam™, you will see a charge jump the space between the pie pan and your finger as the electrons are repelled toward Earth, or grounded. When the pie pan is lifted off the Styrofoam™ using the insulating handle (Styrofoam™ cup) and your finger is once again brought near the pie pan edge, a second charge may be seen as the electrons return through the air from your finger to the aluminum pie pan. This can be repeated over and over again without much electrical charge loss from the Styrofoam™ plate. Students may think that materials that lose electrons have lost them permanently. The electrophorus demonstrates how electrons are not lost, but are transferred from one conductor to another.
After students have experimented with the discharge of electrons from and to the pie pan, they are asked to attach a sewing needle to the edge of the pie pan, pointed side out. The needle acts as a lightning rod. Sharp-pointed conductors, such as lightning rods, when attached to a building’s highest point, allow electrons to escape from the building’s outer surfaces to the sky, instead of through the building. The needle on the pie pan keeps the pie pan from building up an observable charge.
Intended Learning Outcomes:
Begin the activity by giving each student a Static Starter Kit (salt and pepper mixed, a plastic spoon and a piece of woolen fabric). Ask the students to carefully dump the salt and pepper mixture onto their desk top. Without mentioning the word “static,” give them the challenge to use the other items in the kit to separate the salt from the pepper. They CANNOT touch the salt or the pepper with anything to accomplish this task. (Teacher hint: By quickly rubbing the bowl of the spoon with the woolen fabric and then passing the spoon just above the salt/pepper mixture, the static created will cause the pepper to jump onto the bowl of the spoon.)
Burns, Marilyn. (2005). Looking at how students reason. Educational leadership, Volume 63.3, pp. 26-35.
All students need to learn scientific skills, such as observation and analysis. Active, student-centered inquiry, in which students learn to apply scientific problem solving, should be at the core of science education. Learning through well-planned activities and experiences promotes cause and effect thinking and the questioning of observed events and resulting data.
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