Toward instructional design principles: Inducing Faraday’s law with contrasting cases

Although physics education research (PER) has improved instructional practices, there are not agreed upon principles for designing effective instructional materials. Here, we illustrate how close comparison of instructional materials could support the development of such principles. Specifically, in discussion sections of a large, introductory physics course, a pair of studies compare two instructional strategies for teaching a physics concept: having students (i) explain a set of contrasting cases or (ii) apply and build on previously learned concepts. We compare these strategies for the teaching of Faraday’s law, showing that explaining a set of related contrasting cases not only improves student performance on Faraday’s law questions over building on a previously learned concept (i.e., Lorentz force), but also prepares students to better learn subsequent topics, such as Lenz’s law. These differences persist to the final exam. We argue that early exposure to contrasting cases better focuses student attention on a key feature related to both concepts: change in magnetic flux. Importantly, the benefits of contrasting cases for both learning and enjoyment are enhanced for students who did not first attend a Faraday’s law lecture, consistent with previous research suggesting that being told a solution can circumvent the benefits of its discovery. These studies illustrate an experimental approach for understanding how the structure of activities affects learning and performance outcomes, a first step toward design principles for effective instructional materials.

Figure 1

A set of contrasting cases of wire loops in magnetic fields (adapted from the University of Washington Tutorials in Introductory Physics [8]).

Figure 2

An excerpt from the BPC materials. Students are asked to use the Lorentz force to predict whether there is an induced current.

Figure 3

The examples provided in the CC materials.

Figure 4

Experimental timeline for study 1.

Figure 5

Mean post-test score, split by instructional materials and preactivity lecture attendance. There is no performance difference by instructional materials, but there is an advantage for attending lecture. All error bars denote one standard error.

Figure 6

Diagram of a metal ring in an external magnetic field, along with a graph of external magnetic field vs time.

Figure 7

The distribution of scores on the delayed post test for CC and BPC. The difference between the distributions is reflected in the low tail for BPC and the greater ceiling effect for CC at scores of 14 and 15.

Figure 8

Experimental timeline for study 2.

Figure 9

Qualitative Faraday’s law post-test scores, controlling for previous midterm score, broken out by instructional materials and lecture attendance. All error bars denote one standard error.

Figure 10

Subsequent topics post-test scores, controlling for previous midterm score, broken out by instructional materials and lecture attendance. All error bars denote one standard error.

Figure 11

Mean enjoyment ratings of the discussion section activities, split by materials and preactivity lecture attendance. All error bars denote one standard error.