Writing to Learn: A Circuits Laboratory Report Without Numbers
As a new instructor trying to put together physics courses for a residential high school of motivated students, I was scrambling late into the night almost every day. Inspiration at 2 o'clock in the morning would lead to a class activity performed only a few hours later. Much of the time, there was not enough proper equipment for the experiment so we would improvise with whatever was in the room to make things work. Students actually commented that they enjoyed these "MacGyver" experiments which seemed to be put together with bubblegum and paper clips! Out of these inspired nights came a few experiments that I continue to use ten years later in a well equipped lab.
One late night while trying to prepare an experiment with resistance, I was reading an American Journal of Physics article about student understanding of simple electric circuits . The set of circuit questions used by the authors for their study was provided in the text and I had enough equipment for my classes to construct these circuits in the laboratory. To turn this into an experiment requiring a report, I needed something more than having students simply choose the answer to the multiple choice questions. In addition, I did not have time to perform almost fifty one-on-one interviews with students each semester like those documented in the article. After some more thought, I realized that students could write a paragraph about the physics of each of the circuits and thus began what they affectionately came to call "The Essay Lab."
The design of "The Essay Lab" is this: After completing the introductory material about circuits and Kirchhoff's rules, students are given a set of multiple choice questions related to simple circuits (batteries, light bulbs, wires, and switches) that they answer in their lab groups. A sample question with the data table of the required measurements students need to make from the activity is provided in Fig. 1. Each of the questions is written so that there is a change in the circuit (a switch opens or closes, a light bulb is unscrewed from its socket, and so on) and the answers are related to how quantities associated with the circuit (current, voltage, bulb brightness, power) do or do not change. After debating all of the questions, lab groups construct each of the circuits, record a set of prescribed voltage and current measurements, and then record the same set of measurements after making the required change in the circuit. Once data is collected, the groups debate the questions again. Based on casual observation of responses, the groups answer only 20–30% of the questions correctly before conducting experiments. When there is not enough time for groups to make all of the required measurements (during a 2-hour class), data is provided to them.
Now that they have data for each circuit, students write fully-formed essays explaining the physics of the circuit… but the data cannot be used in the essays! The data provide a "safety net" to check arguments before they are committed to paper. If someone reasons that the current in the circuit increases, the data allow for a determination of whether or not that statement is true; in the essay, it cannot be argued that the current increased because "we measured that." For each essay, there must be correct physical reasoning not only justifying the correct choice, but also explaining why the other choices are incorrect. In this way, students need to make qualitative arguments describing the physics of all aspects of the circuits. A sample essay is provided to classes as a way to help students understand what is expected in the write-up.
Typically, the activity consists of 8 - 10 circuits with the essays due in stages over the course of five weeks. This allows me time to provide feedback to students about their work before the next set of essays is due. Especially after the first essays are returned (and grades are not that great!) there is an increase in attendance at office hours before the next set of essays. This actually reduces the amount of time spent grading because after several revisions, many essays need no corrections and receive full marks. Also, as students recognize their own misconceptions and address them, the quality of writing improves over the course of the five weeks.
Grading a large number of essays can be time-intensive, but having students write about physics gives me insight into how they think through problems. This information allows me to adjust classroom presentations and activities in order to address misconceptions that appear commonly in their writings. Over the past 7 years while teaching at Delta College, more than 200 students have completed "The Essay Lab" from sections of my calculus-based E&M course. As a check of their understanding, the DIRECT exam on basic circuits is given during the final week of the class . The average score by my sections on this assessment is 68% (52% is the national average for university students). These results show that even though there is extra effort to read many essays, it is worth the extra time since misconceptions are being dealt with directly. Though I cannot compare scores on DIRECT from students that have not written essays (because all of my classes do so), students have told me that they felt this was a worthwhile experiment because they learned a lot. Also, when students return to visit after taking subsequent courses in electricity or circuits at other colleges, they tell me that they were extremely well prepared for these courses.
To increase student understanding and to learn what they are thinking, essays are a great pedagogical tool. While it is more work to read and grade multiple essays from a single experiment report over the course of several weeks, what is gained from the experience makes it worthwhile for both the student and their instructor. At least it does for me!
- The ammeter reading increases.
- The potential difference between B and C stays the same.
- Bulb #3 lights up more brightly.
- The potential difference between E and F decreases.
- The power supplied by the battery stays the same.
|Before Change||After Change|
|Current through ammeter||Current through ammeter|
|Voltage from B to C||Voltage from B to C|
|Voltage from E to F||Voltage from E to F|
|Voltage from F to G||Voltage from F to G|
 R. Cohen, B. Eylon, and U. Ganiel, "Potential difference and current in simple electric circuits: A study of students' concepts," Am. J. Phys. 51, 407–412 (1983).
 P.V. Engelhardt and R.J. Beichner, "Students' understanding of direct current resistive electrical circuits," Am. J. Phys. 72, 98–115 (2004).
Michael Faleski is an Associate Professor of Physics at Delta College in University Center, MI.
Disclaimer - The articles and opinion pieces found in this issue of the APS Forum on Education Newsletter are not peer refereed and represent solely the views of the authors and not necessarily the views of the APS.