### Notes:

The Electric Field Intensity Concept Builder is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. The size of the Concept Builder can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.

### Teaching Ideas and Suggestions:

Electric Fields are a common topic in first-year Physics courses. The topic is both conceptual and mathematical. This exercise takes a mathematical approach, but not the more typical plug-and-chug approach. Rather, this Concept Builder puts an emphasis on understanding the relationships of the electric field equation. There are three activities in all. Eah activity is indepenent of the other. Each question in every acivity involves the analysis of a diagram that contains information about the quantity of charge (Q) on the source charge and the separation distance (R) between the source charge (it's center) and a location surrounding it.

In the first activity (perhaps the hardest of the three), students must rank three locations according to their electric field strength. Relative values of source charge and separation distance are given. The values are expressed symbolically - Q, 2•Q, 3•Q, etc. - and not numerical values. So plug-and-chug is not possible. The equation E = k•Q/R2 must be used as a guide to thinking. Proportional reasoning skills must be applied to make the rankings.

In the second activity - Case Studies - students must analyze two different cases and determine which case has the greatest E value and by what factor. Once more, the values of charge and separation distance are are expressed symbolically - Q, 2•Q, 3•Q, etc. - and not as numbers. And once more students must use the electric field equation as a guide to thinking about how variations in distance and charge affect the electric field value.

The final activity is all about the inverse square relationship between E and R.  The value of E is given for a location X and students must calculate the value of E at location Y. The two locations are marked and labeled on a diagram with concentric circles to mark the 2R, 3R, and 4R distances from the center of the source charge. Students must use the inverse square relationship to calculate the value of E at location Y.

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 que 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.

### Related Resources

There are numerous resources at The Physics Classroom website that serve as very complementary supports for this Electric Field Concept Builder. These include:
• Minds On Physics Internet Modules:
The Minds On Physics Internet Modules include a collection of interactive questioning modules that help learners assess their understanding of physics concepts and solidify those understandings by answering questions that require higher-order thinking. Missions SE10, and SE11 of the Static Electricity module provide great complements to this Concept Builder. They are best used in the middle to later stages of the learning cycle. Visit the Minds On Physics Internet Modules.

Users may find that the App version of Minds On Physics works best on their devices. The App Version can be found at the Minds On Physics the App section of our website. The aforementioned assignments can be found on App #4 of the six-part app series. Visit Minds On Physics the App.

• Physics Interactives: Our Physics Interactives section includes a collection of interactive simulations that help students visualize concepts by interacting and observing the relationships between variables. There are three simulations in the Static Electricity section of the Physics Interactives that will coordinate with this Concept Builder. The links are provided below. The Coulomb's Law interactives serves as a suitable pre-cursor to this Concept Builder. The Electric Field Lines and Electric Field Hockey activities are good follow-ups for those courses that emphasize the mathematics of projectiles and its use in solving problems. These include the following:

Electric Field Lines

Electric Field Hockey

• Curriculum/Practice: Several Concept Development worksheets at the Curriculum Corner will be very useful in assisting students in cultivating their understanding, most notably ...

Electric Field

Electric Field Lines

Visit the Curriculum Corner - Electrostatics.

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