Many Physics courses include a unit on Static Electricity. A ommon objective for such units includes explaining how two objects become charged as they are rubbed together. This charging procedure is often referred to as triboelectric charging. Charging by friction is another name used to describe the process, though the term itself is misleading as friction has little to do with the process.The process of charging two objects by rubbing them together is explained by the transfer of electrons from the least-electron-loving material to the most-electron-loving material. The object that loses the electrons becomes positively changed and the object that gains the electrons becomes negatively charged. This Concept Builder addresses this topic.

This Concept Builder consists of three different activities. Those three activities are described as follows:
 

• What's the Charge: Question Groups 1-4. Information about the relative affinity that two objects have for electrons is given; learners must predict the charge that each object would have when rubbed together. They must also indicate the direction of particle transfer (electrons, protons or both) during the charging process.
• Triboelectric Series: Question Groups 5-10. A triboelectric series consisting of 15 different materials is given. Information about the charge acquired by an unknown material when rubbed against two or three of the listed materials is also given. Learners must indicate what area on the series that the unknown material should be placed.
• Rank the Material: Question Groups 11-16. Information about the charge acquired when three or four unknown materials are rubbed together is given. Learners must indicate how the three or four materials should be arranged in a triboelectric series. 

Before using the Concept Builder with your classes, we recommend that teachers attempt each of the activities in order to determine which are most appropriate for your classes and what pre-requisite understanding a student must have in order to complete it. Alternatively, the questions are provided in a separate file for preview purposes.

In order to complete an activity, a student must correctly analyze each question in that activity. If a student's analysis is incorrect, then the student will have to correctly analyze the same or very similar question twice in order to successfully complete the activity. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through an activity, a system of stars and other indicators are used to indicate progress on the level. A star is an indicator of correctly analyzing the question. Once a star is earned, that question is removed from the queue of questions to be analyzed. Each situation is color-coded with either a yellow or a red box. A red box indicates that the student has incorrectly analyzed the question and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the question must be correctly analyzed one time in order to earn a star. Once every question in an activity has been analyzed, the student earns a Trophy which is displayed on the Main Menu. This system of stars and trophies allows a teacher to easily check-off student progress or offer credit for completing assigned activities.

The most valuable (and most overlooked) aspect of this Concept Builder is the Help Me! feature. Each question group is accompanied by a Help page that discusses the specifics of the question. This Help feature transforms the activity from a question-answering activity into a concept-building activity. The student who takes the time to use the Help pages can be transformed from a guesser to a learner and from an unsure student to a confident student. The "meat and potatoes" of the Help pages are in the sections titled "How to Think About This Situation:" Students need to be encouraged by teachers to use the Help Me! button and to read this section of the page. A student that takes time to reflect upon how they are answering the question and how an expert would think about the situation can transform their naivete into expertise. 

 

 

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Triboelectric Charging Concept Builder. These include:
 

 

 

Additional resources and ideas for incorporating this Triboelectric Charging Concept Builder into an instructional unit on Static Electricity can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.