Conceptual and procedural items In the Introduction, we argued that a proper conceptual understanding enables students to reason about potential differences and the flow
and the intensity of current . Therefore, the conceptual items on the test required participants to reason about
the behavior of current and potential difference in various DC circuits, including series,
parallel, and mixed connections. (At this stage, the curriculum and the textbook treated resistance as a constant.) In some conceptual items, participants were given two circuits
(e.g., one circuit with two light bulbs in a series connection and another with two light
bulbs in parallel), and then they had to reason about how a specific variable (e.g., current)
would behave in the different circuits. In other conceptual items, participants were given a
circuit in which a certain change took place (e.g., turning a switch on or off). Then they
had to reason about how this change in one parameter would affect other parameters. An
example of a conceptual item is shown in Figure 2.