These textbook-based lessons are often supplemented with practical lessons in which
students can build electrical circuits and carry out measurements. These practical lessons
are essential for developing skills and experience with working with real equipment and,
through experimentation, a conceptual understanding of the domain. However, practical
lessons also have limitations that in general keep students from developing a proper conceptual understanding. For example, in practical lessons students tend to focus on making
their circuits work rather than on trying to understand the causal relations between variables and outcomes . Furthermore, when working
with real circuits, students must deal with many unexpected circumstances and deviations
from what they have learned in the textbook-based lessons. For example, in reality, equip-
ment (circuits, resistors, wires, batteries) is not ideal, and consequently the measurements
in the circuits will show different outcomes than expected purely on the basis of formulas.
Finally, students often do not engage in systematic experimentation, and they rarely if ever
link their hands-on activities with what they have learned in the textbook lessons.