May 10, 2006

Alex Doonesbury is <i>so</i> going to Cornell

It's probably only a tease. In cartoonist Garry Trudeau's May 10 strip, Alex Doonesbury announced that she wanted to go to Cornell. On May 11 she vacillated, considering CalTech. And the logical expectation is that she will end up at Trudeau's mythical, free-thinking Walden College. But at least we're on the short list.

Her positive reaction to Cornell was based on a technical question she has been asking professors from other schools yearning for her: You have two black boxes, each hiding an internal circuit. Using workbench tools, how do you tell which is the current source and which is voltage?

The answer is to hold the boxes in your hand. Since the current source has current flowing through a resistor, it would be warmer.

MIT, according to a previous strip, didn't come up with the correct answer. When admonished that it was a trick question, Alex responded, "But they're faculty!"

On Wednesday morning, a Cornell "professor" got it right, and Alex said to her father, "I'm so going to Cornell!"

We haven't found out which Cornell professor it might have been, but Clif Pollock, the Ilda and Charles Lee Professor of Electrical and Computer Engineering and director of the School of Electrical and Computer Engineering, commented, "It had to be either me or the dean."

"I ask that question in my class when I teach ECE 210 [Introduction to Circuits]," he said, chiding Trudeau a bit for having an MIT professor get it wrong, which he doubted would happen. He echoed the unnamed Cornell professor in the strip by saying, "It's a fun question." He added that Cornell also would be a good choice for Alex Doonesbury because the university has a strong program in micro-optics, in which she had expressed interest in earlier strips.

Then again, a Cornell professor (requesting anonymity) insisted, "It had to be Lois Pollack." Pollack is Cornell assistant professor of applied and engineering physics and director of undergraduate programs in engineering physics. Since Cornell is working hard to increase the number of women applicants to the College of Engineering, it would have been appropriate for Alex to deal with one of the women faculty members in the college. "I handle all the admissions requests for this department, and I do get quite a few calls referred from the admissions office," Poillack said.

"I do teach that topic in honors freshman physics, but I don't use that question in class," she said.

By noon on the day the strip appeared, it had already generated several positive comments on the Slate magazine "Blowback" page, mostly from Cornell grads. Liz Cowles '82 wrote, "Cornell wins!? What a pleasant surprise! Good choice, considering Cornell has the best ice cream in the Ivy League."

For those who are wondering, the Cornell professor in the strip refers to Thévenin and Norton equivalent circuits. A Thévenin equivalent circuit consists of an "ideal" power source (one that doesn't vary under load) in series with a resistor. A Norton equivalent circuit has the same ideal source in parallel with a resistor. In the latter, current is constantly flowing through the resistor and would heat it up. However, Pollock noted, current flowing in a loop in the Norton circuit also generates a magnetic field, which provides another way to distinguish current source from voltage.