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Sorting Trash with Static Electricity


Bruce C. Palmquist
Department of Physics / Department of Science Education
Central Washington University


Recycling plastic is an effective way to reduce waste in landfills. However, in order to effectively reuse recycled plastic, different types of plastics must be separated from one another. This is a time intensive task. Engineers in Japan have tested a way to separate plastics using static electricity. In this interrupted case, students will design a method to separate plastics using static electricity, make hypotheses based on what the Japanese engineers did, and analyze their actual data with a focus on bar graphs. The case can be used as a course transition from electric charge to electric fields. Students should have prior knowledge about the triboelectric series and Coulomb's Law; they should also be familiar with the basic kinematic equations for objects moving with constant acceleration. Although originally developed for an introductory calculus-based physics class, calculus is not required, and so the case can easily be used in an algebra-based college physics class or even a high school physics class that covers static electricity concepts.

  • Use the triboelectric series to predict the relative strength of a charge.
  • Apply the definition of electric field and basic kinematic equations to determine the relationship between charge and displacement.
  • Design an experiment, specifically describing the basic procedure, number of trials, equipment needed, and method of analysis.
  • Given an experimental set-up, sketch a graph of a hypothetical outcome.
  • Given a description of the axes of a graph, develop and defend a conclusion based on the graph.
Keywords: Static electricity; electricity; electric field; charge; triboelectric; recycling; plastics; experimental design
Topical Area: N/A
Educational Level: High school, Undergraduate lower division
Formats: PDF
Type/Method: Interrupted
Language: English
Subject Headings: Physics   Electrical Engineering   Engineering (General)  
Date Posted: 3/20/2014
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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