Investigating introductory student difficulties reading equipotential diagrams

Abstract

This study investigated student difficulties reading equipotential diagrams and the effect a visual change to these diagrams had on students' ability to interpret these diagrams. Equipotential diagrams are often drawn with a uniform line thickness and color. We modified the equipotential diagrams to use color variation and line thickness to indicate the sign and strength of the potential. These changes, which are consistent with theories of visual attention and grounded cognition, exploit students' innate ability to perceive color and line thickness variations to communicate the electric potential. Students compared electric potentials between indicated points on given traditional or modified diagrams. Results show that these students, even after instruction, responded with a distance only electric potential rule. In addition, we found that the modified diagrams did not have the predicted positive effect on students' ability to rank electric potentials; we suspect this is because students' rule for electric potential did not account for charge sign.

Changes to equipotential diagrams to improve student ranking of electric potential

“…A 2018 study in the same course [5] on the effects of modified vs. traditionally drawn equipotential diagrams found that, combining data from both conditions, the mean correctness rates were 59% correct on the traditional diagrams and 63% correct on the modified diagrams, and were 61% correct on the first set of questions and 63% correct on the second set. Students presented with traditional diagrams first, followed by modified diagrams did 9% better on the second set of diagrams.…”

“…The predominant findings of the prior study were that modification to the equipotential diagrams resulted in increased gaze time, and that the increased gaze times did not result in increased correctness rates. Students neglected the sign of the charge in their responses and followed a "closer is higher electric potential" rule 78% of the time regardless of the sign of the charge [5].…”

“…A prior study with modified equipotential diagrams found that students pay increased attention to the enhanced features of the diagram, but do not have an improved correctness rate of ranking the electric potential, partly because they do not take into account the charge sign [5]. The study used colors in the diagrams (blue for positive, red for negative), changes in color intensity, and variations in equipotential line thickness, in addition to conventional proximity to sources of charge to indicate charge sign and electric potential.…”

“…These issues have been well explored and include issues with electrical potential energy, relating the electric potential to the electric field, and connecting electric potential and current flow [1][2][3]. Other common difficulties involve assigning electric potential for conductors, the choice of the zero point [4], and the importance of charge sign in determining the electric potential [5].…”

“…There has been extensive research on student difficulties with interpreting and applying data from pictorial and graphical sources such as free-body diagrams and motion maps [6,7], however, there has been relatively little research on student issues with equipotential diagrams. Two such studies on equipotential diagrams were reported in the 2013 and 2018 PERC Proceedings [5,8].…”