Case of two electrostatics problems: Can providing a diagram adversely impact introductory physics students’ problem solving performance?

Drawing appropriate diagrams is a useful problem solving heuristic that can transform a problem into a representation that is easier to exploit for solving it. One major focus while helping introductory physics students learn effective problem solving is to help them understand that drawing diagrams can facilitate problem solution. We conducted an investigation in which two different interventions were implemented during recitation quizzes in a large enrollment algebra-based introductory physics course. Students were either (i) asked to solve problems in which the diagrams were drawn for them or (ii) explicitly told to draw a diagram. A comparison group was not given any instruction regarding diagrams. We developed rubrics to score the problem solving performance of students in different intervention groups and investigated ten problems. We found that students who were provided diagrams never performed better and actually performed worse than the other students on three problems, one involving standing sound waves in a tube (discussed elsewhere) and two problems in electricity which we focus on here. These two problems were the only problems in electricity that involved considerations of initial and final conditions, which may partly account for why students provided with diagrams performed significantly worse than students who were not provided with diagrams. In order to explore potential reasons for this finding, we conducted interviews with students and found that some students provided with diagrams may have spent less time on the conceptual analysis and planning stage of the problem solving process. In particular, those provided with the diagram were more likely to jump into the implementation stage of problem solving early without fully analyzing and understanding the problem, which can increase the likelihood of mistakes in solutions.

Figure 1

Diagram for problem 1 provided to students in the DO group.

Figure 2

Diagram for problem 2 provided to students in the DO group.

Figure 3

Percentages of students from each intervention group (PO, DO, and NS) who earned a score of 4 or less, earned a score of 5, 6, or 7, or earned a score above 8.

Figure 4

Suzana’s solution to the additional problem (left) on which she worked first and problem 2 (right), on which she worked last.

Figure 5

Calvin’s work to problem 2 (second problem solved in interview).

Figure 6

Calvin’s work to the additional problem (last problem solved in interview).

Figure 7

Worked out solutions for problems 1 (left) and 2 (right) along with how many points were assigned to each part of the solution. Both problems can be solved using two equivalent methods and both methods are shown.