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Using a fast-pulsing laser, physicists have recorded the first moments of electrical resistance, the friction that generates heat as electricity travels through circuits.

Physicists knew electrical resistance didn’t kick in the moment a voltage was applied. Electrons experience some freedom before slowing to a crawl and scattering. What wasn’t certain was how quickly they make that transition (illustrated in the animation above, with electrons in blue, “electron holes” left by departing electrons in red, and voltage signified by the green arrow).

I explained that we were building the model we’d be using to predict the behaviour of circuits for the  next two years, and that on tests, I would be evaluating whether they used their model in a well-reasoned way (“You’re going to grade us based on what we say??”  They were astounded).  I cautioned them against rejecting things too quickly, since they would need as much structure as they could get. 

After each presentation, we discuss it and voted on it.  For voting, they used the feedback flashcards I’d made in September.  Green means accept; red means reject; yellow means “I have a question or want something clarified”. 

The lecture backlash signals an evolving vision of college as participatory exercise. Gone are the days when the professor could recite a textbook in class. The watchword of today is “active learning.” Students are working experiments, solving problems, answering questions — or at least registering an opinion on an interactive “smartboard” with an electronic clicker.

The lecture backlash signals an evolving vision of college as participatory exercise. Gone are the days when the professor could recite a textbook in class. The watchword of today is “active learning.” Students are working experiments, solving problems, answering questions — or at least registering an opinion on an interactive “smartboard” with an electronic clicker.

A new biology course had 22 freshmen fan out across campus last fall for dirt samples, from which each student culled a new and heretofore unknown virus. Now, the class has picked one virus for genetic mapping.

Not all the ideas are new. At the University of Maryland College Park, engineering professors eliminated introductory lecture courses in 1991. Since then, students have spent the crucial first year engaged in actual engineering, building swing sets, helicopters and hovercrafts.