Notes

Many Physics courses include a unit on Static Electricity. For such courses, one central concept is the distinction between conductors and insulators and the effect that these types of materials have upon electron flow. Another key concept is the manner in which objects can be charged by contact or conduction and the vital role that conductors have in this process. And finally, the concept of grounding is a typical topic in such course. This Concept Builder targets all three ideas - conductors versus insulators, charging by conduction, and grounding. We recommend its use near the end of a learning cycle on charging and grounding, following lab work and class discussion.

This Concept Builder consists of three Difficulty Levels. Those three levels are described as follows:

• Apprentice Difficulty Level: Question Groups 1-4. Each question describes the initial charge state and the material type (conductor or insulator) of an object. Students must determine the final charge state of the object after it is touched to a charged object or the ground.
• Master Difficulty Level: Question Groups 5-12. Each question describes the initial charge state and the material type (conductor or insulator) of two connected objects. Students must determine the final charge state of the two objects after one of them is touched to a charged object or the ground.
• Wizard Difficulty Level Question Groups 13-20. Each question describes the initial charge state and the material type (conductor or insulator) of three connected objects. Students must determine the final charge state of the three objects after one of them is touched to a charged object or the ground.

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. We believe that all three levels are do-able and profitable exercises. We recommend starting at the Apprentice Level and continuing through the Wizard Level.

We gave considerable thought to how we represent the charge on conductors and insulators in this exercise. Charge on conductors is spread over the surface but charge on insulators tends to be localized to the location of chargie acquisition. As such we represented the charge on conductors by + and - signs positioned on both ens of the rectangles. In contrast we represented the charge on insulators by smaller + and - signs positioned on a single end or corner of the rectangle. We also assume in this exercise that all charging occurs (when it occurs) by the process of conduction. Put another way, we assumed that air acts as a perfect insulator and does not allow for the movement of electrons from one object to another object, a process that we have referred to at various locations on our website as charging by lightning.

In order to complete a difficulty level, a student must correctly analyze each question in that level. 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 level. 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 a level 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 Conductors and Insulators Concept Builder. These include:
 

Additional resources and ideas for incorporating this Conductors and Insulators 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.