  Classroom response systems (CRSs) can be potent tools for teaching physics.
Their efficacy, however, depends strongly on the quality of the questions used.
Creating effective questions is difficult, and differs from creating exam and
homework problems. Every CRS question should have an explicit pedagogic purpose
consisting of a content goal, a process goal, and a metacognitive goal.
Questions can be engineered to fulfil their purpose through four complementary
mechanisms: directing students' attention, stimulating specific cognitive
processes, communicating information to instructor and students via
CRS-tabulated answer counts, and facilitating the articulation and
confrontation of ideas. We identify several tactics that help in the design of
potent questions, and present four "makeovers" showing how these tactics can be
used to convert traditional physics questions into more powerful CRS questions.
