### Notes:

The Ohm's Law 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:

This Concept Builder is intended for use near the early stages of a learning cycle on voltage-current-resistance relationship. Most physics courses spend considerable time using physics formulas to solve numerical word problems. Algebraic manipulation and substitution of known values into the formula is a typical activity. But we think that physics formulas are much more than recipes for solving problems for an unknown quantitiy. Physics formulas are tools to guide our thinking about how a variation in one quantity might affect another quantity in the formula. And that is what this activity is all about. Students think proportionally about the equation, I = ∆V / R. In the prrocess of completing this Concept Builder, students must ponder how an alteration in voltage would affect the crcuit's current. And they must ponder how an alteration in the resistance of the circuit would affect the current. This task is much different than manipulation of a formula and substitution of known values. This task will help students gain a better intuition for the relationship between curent, voltage, and resistance. The activity can be used at about any time during a learning cycle on Ohm's law. But we recommend that it be used quite early and prior to the use of the formula as a tool for algebraically solving physics word problems.

This Concept Builder was intended as an in-class activity. After some early lab work, some discussion of the voltage-current-resistance relationship, and some discussion of the directly proportional and inversely proportional relationships between current and voltage and resistance, allow students an opportunity to interact with the questions. The Concept Builder includes three levels of difficulty. Teachers using the Concept Builder with their classes should preview the activity (or view the Questions in the separate file) in order to judge which levels would be most appropriate for their students. There is some redundancy from one level to another level with each level including questions from the easier levels along with four more questions. Our summary of the three levels is as follows:

• Apprentice Level: Question Groups 1-4. Includes a doubling or tripling of either the voltage or the resistance.
• Master Level: Question Groups 1-8.  One variable is varied at a time. Variations in voltage and resistance can include doubling, tripling, halving, and "one-thirding."
• Wizard Level: Question Groups 1-12. Includes the first eight Question Groups plus four additional groups in which two variables are altered.

We can imagine it being profitable to allow students to make judgements as to what level to begin with and to progress from easier to more difficult levels.

In order to complete a level, a student must correctly analyze each question at 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 a level, 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 cue 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 at 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 levels.

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 the Ohm's Law 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. Assignments EC4, EC5, and EC6 of the Electric Circuits 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 Electric Circuits module can be found on Part 4 of the six-part App series. Visit Minds On Physics the App.

• The Calculator Pad: The Calculator Pad section of our website focuses on the use of mathematical formulas in solving Physics word problems. Each topic includes a set of 25 to 35 problems of varying difficulty level. All problems are accompanied by an audio file that describes how to go about the solution to the problem. Additionally, each problem has a link that hides and shows the answer and each problem set has a page devoted to a discussion of the fundamental formulas and their use.

Visit the Calculator Pad - Electric Circuits.

Additional resources and ideas for incorporating Ohm's Law into an instructional unit on Electric Circuits can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.