The Genecon-capacitor conundrum

I'm a big fan of Genecons. They're simple, versatile, and fairly rugged. They were designed for classroom use, and I use them in many classroom activities. Even jaded high school students love cranking the handle to light a bulb. A number of Genecon activities can be found in the circuits and magnetism sections of The Book of Phyz.

The high-tech one farad capacitors are also well-suited for classroom use. A Genecon and a 1 F cap? Two great tastes that taste great together!

One engaging activity is to connect Genecon to capacitor, crank, and release. The cranking charges the capacitor. Upon releasing the handle, the capacitor powers the Genecon as a motor. See the video below.

But there's something strange here. The handle rotates in the same direction is was being cranked.

We expect the handle to turn back from whence it came, as if our cranking had wound up a rubberband motor. Upon release, it should go back the other way! Nevertheless, the capacitor-powered Genecon motor turns the same way we cranked it to charge the capacitor.

Why?

I make my attempt to explain the conundrum in this interactive QuickTime presentation. It's a 24 MB download (it took about a minute to download on my DSL). I'm sure it needs polishing and further clarification. Your comments will help determine what's needed to improve it.

Linsey Marr: RA alum and VT prof*

Rio Americano and Virginia Tech had the same "first day of school" this academic year. I had barely returned from a trip to Yellowstone in time to start the school year. My friend and former student, Linsey Marr cut her summer travel even closer to opening day. Air travel complications conspired to delay her return to Blacksburg and forced her to call ahead to cancel her classes at Virginia Tech. But a shooting rampage on campus early on August 21, 2006 resulted in all classes being cancelled that day.

Linsey was an academic superstar at Rio in the early '90s. She was a well-balanced student with performing arts and athletic skills as well, but there wasn't a class on campus that truly challenged her academic/intellectual abilities. My AP Physics class certainly didn't. She smoked every class she took without appearing to break a sweat. Linsey and her Science Olympiad Cell Biology teammate scored the first national competition-level gold medal for Rio Americano.

From Rio, Linsey went on to MIT but transferred to Harvard and majored in environmental engineering. While there, she designed (and built) a fluorescent version of the then-ubiquitous torchiere lamp. It scored notice as one of Popular Science's "Best of What's New." Serious challenge, though, continued to elude her: she graduated summa cum laude... from Harvard! It's not that challenges didn't come her way, it's just that she dispatched them in ways most of us could not.

Linsey returned to California to earn a Ph.D. at Berkeley. And when it came time to choose among the tenure-track positions at leading environmental engineering schools, she chose Virginia Tech. She continues to distinguish herself there.

When the reports began coming in about the shootings at VT last Monday, I became concerned. Initially, it was "just" a shooting at a dorm: two dead. I thought to myself, "this is strike two, Linsey." But when the subsequent reports told of more than 20 dead in a massacre in an engineering building, I began to feel sick.

While trying to maintain a calm appearance for my students (who weren't aware of the news and likely had no direct connection to VT)), I searched the 'net to determine which building was involved, which building Linsey's office was in, and what their proximity was. The reports only got worse throughout the day. "More than 20" became "more than 30." Names of the victims were not being released.

I was anxious to know how she was, but I knew there were many others who deserved more immediate responses, so I held off trying to contact her. Phone lines into Blacksburg were overwhelmed. Linsey was able to tell me she was not harmed in the shooting when I emailed her late Monday night. The language is tricky here. Better to say she was not struck by a bullet; everyone in the Blacksburg/Virginia Tech community was harmed. She was two buildings away during the shootings and saw the swarm of ambulances descending onto campus.

My thoughts remained with her as I heard the horrific accounts of the shootings. She knew several of the victims personally, and conveyed remembrances of her fallen colleague and several of her students. Difficult to read, but I imagine even harder to write.

This has no doubt been the longest week of Linsey's life. I know she has an exceptionally strong character that will help her through this difficult process. And I imagine that soon enough (if it's not happening already), Linsey will be helping those around her cope with the aftermath of this tragedy. I wish--as we all wish--a full recovery for her and for her community.

Click her pic to get her page.

*Technically, she's an Assistant Professor, but that "Assistant" modifier will probably last as long as a baby porcupine's toy balloon.

ExploratoRio 2007

This year's ExploratoRio was visited by low temperatures and rain. But it was also visited by parents, teachers, and administrators. More importantly, it was visited by elementary school students from Del Dayo, Gold River Discovery Center, Sierra Oaks, and Billy Mitchell.

It was not visited by Channel 31's Good Day Sacramento. Apparently co-host Mark S. Allen made an on-air comment that he would come see us (so as to secure extra credit for a physics student who wrote in to the show). ExploratoRio came and went, but not so much as a cameraperson from KMAX showed up. Wait--a TV personality made an on-air promise that he didn't keep? Color me astonished!

Nevertheless, it was--as always--the grooviest destination during Open House. The hard work of our physics students paid off handsomely. The elementary teachers reported that the rest of the day back in their classroom was essentially lost to enthusiastic tales and questions surrounding the science they saw at Rio.

And in a few years, those students will be enrolled in our course and have the chance to build their own exhibits and thrill "the next generation."

This year, I left all photography to selected students. Here is their work.
http://phyz.smugmug.com/gallery/2746132.

The AAPT PhysicsBowl: strikes and gutterballs

The American Association of Physics Teachers hosts an annual high school competition exam called PhysicsBowl. It's a forty-question test to be completed in 45 minutes by examinees. High schools pay a per-test entrance fee to obtain exams and enter into the competition. The exam is administered at school-site classrooms throughout the country in early April. Schools send the Scantron-type student answer sheets to a national office where they are scored and ranked.

Schools compete within about 16 regions. Rio Americano typically competes in a region that includes California, Hawaii, and US Protectorates. (The winning schools and scores in this region often come from top-shelf schools in Hawaii!). The competition is also partitioned by level: first-year physics students in one division and second-year/AP Physics students in another. A school's score is determined by the four best scores returned by that school--known only after scoring at the national office.

At Rio, we have competed every year since 1991. We have won our region and division two times and come in second place twice. We have also had individual student score recognition. All noted in our PhysicsBowl Hall of Fame. There are prizes for winning schools and top-scoring students.

I order tests and administer PhysicsBowl to my AP Physics 2 students, so we compete with the best and brightest in our region. I give my students practice tests to study and offer them extra credit based on their Physics Bowl performance. And when we win our region/division, I waive the second semester final exam for the whole class.

Generally speaking, I like the PhysicsBowl. The questions are difficult: the mean is low and the distribution is unsettlingly normal (a bell curve you wouldn't want on a criterion-referenced test taken by high-achievers).

What I don't like about PhysicsBowl is the inclusion of college topics. Developing the operational form for a difficult, nationwide competition exam is no mean feat. But the content should truly be limited to what you can find in a high school physics book and/or listed in state documents of high school physics standards. So questions about charge distribution or electric field strengths in concentric conducting shells don't need to be there.

When opened to college physics content, some truly wild questions can be brought in. But what's the point? If securing a well-distributed bell curve is the justification, why not add Lagrangians, Hamiltonians, and Bessel functions?

Clearly, it would be unfair to expect high school students to possess mastery of upper-division physics topics. I would argue that high school students should not be expected to have mastered college physics, either. High school physics they should know, and know well. But not college physics. And trust me, it's far from impossible to generate low-mean questions for all audiences in the content areas of high school physics.

Coach VerDuin to many, Uncle Jack to me

My uncle passed away in my hometown of Grand Rapids, Michigan on April 9th. He was my mother's brother, husband of my Aunt Glo, father of my cousins, Miki, Mike, and Jami, and grandfather to my nieces Whitney, Briana, and Kaylee, and nephews Brandon and Jordan. All of us in the extended family will miss Jack VerDuin.

He was an excellent athlete, teacher, and coach, too. He crafted a long and successful career as Wyoming Park High School's varsity football coach, so he touched hundreds upon hundreds of lives. Countless of his charges were eager to share with others what Coach VerDuin meant to them.

His football program was successful by the pedestrian measure of wins and losses, to be sure. His teams won over 240 games, many conference championships and a state championship. But he enjoyed another kind of success as well. He had the rare gift that true coaches have. They call him a coach's coach. He practiced the alchemy that turned boys into men on the football field. Many who coach do not have this magic.

And many who do risk being under-appreciated because if their ratio of W's to L's isn't high enough. It's been a long time since my own school's football team has had a "winning" season, but I wouldn't trade our coach for any in the area. Rio's Coach Smith has the magic that my uncle possessed, too.

Growing up in Grand Rapids, Friday night football was a strong tradition. The Baird clan would join the VerDuin clan in the stands at Wyoming Park's home and away games. We'd scream and throw confetti (anyone remember confetti?) and we were nearly always on the winning side. In later years, we'd reconvene at Florentines (a local Italian restaurant) for pizza and pop.

The good vibe was so strong that I considered abandoning my own attendance area school track to attend Wyoming Park. Greener grass, some might say. In the end, I stuck with my Riverside roots through to Creston Senior High. But I'll add that episode to the many accounts of what a "larger-than-life" figure my uncle was. He created an attraction to his school for someone who was in no danger of donning helmet or pads.

Here's a note from the Grand Rapids Press. And some kind words from a local sportswriter.

Spring Break Arizona

UPDATE: The best photos can be found here.

The build-up to this year's ExploratoRio was interrupted at its peak. Spring Break inserted itself between the final preparations and the event. With nine days of forced vacation, what to do? Oh: how about a trip to Arizona to once again get red rock dirt on my hiking boots?

The plan is to fly to Phoenix and rent a car. Then drive to Meteor Crater and Painted Desert (Petrified Forest). Next a drive/hike in Petrified Forest and up to Chinle for a recon pass through Canyon de Chelly. Then up to Monument Valley. From there, to Page and the Antelope Canyon slots (canyons, not casinos). Then down to Grand Canyon for a few days. Lastly, a night in Sedona in search of a healing energy vortex. Or not! Then fly back to Sactown in time for school.

Anyway, photos will trickle in here:
http://phyz.smugmug.com/gallery/2660838.

Enjoy!