As we return from a two-week Winter Break, students need a transitional day between their pre-break investigation activity and their in-class presentations. Those presentations are scheduled for the next two class periods. In addition, midterm exams are next week, so I want to provide students with the resources to be successful on the Physics exam, without taking too much time away from presentations.
Today's lesson allows me to set the stage for the next three class meetings: two reserved for presentations and the third day for the exam. Because I value the process of science as much as the content, I am counting the presentations as 50% of the midterm exam grade, with the actual exam itself accounting for the other 50%.
As a way of harkening back to the work we did just before our winter break, I present a warmup problem that underscores some of the key ideas with which each team wrestled. In this three-part warmup, I can accomplish several important goals.
In the first part, students need to find the relationship between power, voltage, and current in order to come up with the correct answer. This is a low-order task but will help to dust off any mental cobwebs that have set in during the break.
In the second question, students need to connect the ideas of power and energy. I can help stimulate that thinking as I circulate around the room and ask students to think carefully about the units we've been using for power (watts, naturally, but also joules per second). If students can think of power as a rate of energy being delivered (or received), this second question becomes simple.
The final question requires a multi-step approach. Students need to recognize that the voltage across the 8-ohm resistor and the current that runs through it will both be necessary to calculate power. There are several solutions though each has its own level of higher-order thinking associated with it. One such solution is provided.
Finally, the overall structure of the circuit in this problem allows me to remind students about the general problem all students face; how to record the electric energy provided by a power supply and how to measure the energy was ultimately transformed into their "black box" device (light bulb, buzzer, etc.). This warmup allows us to revisit the idea of measuring the output power from the supply and the dissipated power by their station's device.
I give students a few minutes to get started on these, working in their notebooks either individually or in small groups, before I begin to address questions and stimulate conversations. Much formative assessment occurs during this time. After ten minutes or so, I show solutions and discuss strategies for tackling these problems.
Students are given time to meet with their teammates to add to their presentation documents and, by the end of class, identify "final tasks" need to be taken before next class. These final tasks become the students' homework.
Here a team takes a few moments to share their work with two students who have just joined us after a semester abroad:
Generally, given the fact that the presentation scores will count as half of the midterm exam grade, students groups are very highly motivated. Here is a quick view of the activity in the room.
My role throughout this time is to address any lingering questions that students have about either the content (conversions between units, ways to present data, etc.) or the process. We continue in this mode for at least 30 minutes, though I am willing to extend the time as long as a) students are being productive and focused and b) the need to complete the presentation persists. Should either of these factors not be present, I ask students to move into a more individualized preparation - reviewing problems in advance of the midterm exam.
Before the class is over, students contribute their final tasks to the document that is available at my computer and projected onto the Smartboard. Here are the final tasks as identified by my students:
As we do not use a textbook, I think it is incumbent on me to provide students an extremely clear sense of the breadth of coverage for any major test, like our upcoming midterm exam. In other words, I can't just say "Chapters 1 through 5." Furthermore, I think it's good practice to be transparent about expectations. To those ends, I provide my students with a set of midterm preview questions.
I tell my students that the word "preview" is intentional as it signals a perfect alignment between those questions and the exam questions. I will use fewer questions and change the numbers but the style and content of the questions will not be different. To further stimulate a deep investment in these questions, I also supply a set of solutions to preview questions which will be electronically posted to our course management system. In principle, any student should be able to use the questions and solutions to fully prepare for the exam. No problem on the exam should look unfamiliar to the well-prepared student.
During the tail end of this class, students are allowed time for their individualized preparation for the exam. Students are encouraged to collaborate and discuss approaches to the questions. I circulate to jog memories, scaffold problems, and generally help students think through these problems.
This is the only time set aside for exam review in class; all other review efforts must happen outside of class. Students leave knowing that our next two classes are dedicated to presentaions.