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27 November 2013

Summer 2014 schedule -- AP Institutes, and perhaps a FREE seminar at Woodberry Forest

James Winterer asks:

Will you be presenting at any AP institutes this summer for the new AP Physics 1-2 courses?
I have three official AP Summer Institutes on the schedule right now:

* Walton High School in Marietta, Georgia June 23-26
* Mahopac High School in New York June 30-July 3
* Manhattan College, August 4-8

I might pick up one more if I get a good offer.  

For those who have attended my institutes in the past, know that my general approach to AP Physics will not change because of the new exams!  The same features of your course that I recommend and model -- quantitative demonstrations; regular, focused experimentation; quizzes, tests, and problem sets based on and graded in AP style -- will produce success on the new AP exams.  In fact, the new exams practically demand some of these features.  So expect much of the same material.  I will certainly bring in some rotation demonstrations, and I'll work with you to recognize how the new exams are different.  But at its heart, the new exams require that we teach thorough physics understanding, which is the same goal we've had for decades.

Would you be interested in an "Open Lab" at Woodberry Forest?  I've been considering offering a free two or three day seminar in my own classroom here at Woodberry.  We would discuss good physics teaching at ALL levels, from conceptual to general algebra-based to college-level to calculus-based.  We'll do some of the same kinds of things I do in my institutes, but with materials that I've developed independently over the years.  Now, I wouldn't be able to offer any official CEUs or whatever.*  But I think we'd have a good and useful time.

*Unless someone else is willing to figure out how to do the paperwork... Dammit, Jim, I'm a physics teacher, not a bureaucrat.

If you might want to attend an Open Lab, let me know in the comment section or by email; suggest a time in July that might work for you.  (Although I'm volunteering my time, you'd need to get yourself here on your own dime, and you'd need to put yourself up in the local hotel.)  If I get enough interest, I'll talk to my school to arrange the details here; I'd rely on crowdsourcing for advertising, so spread the word.


19 November 2013

Exam review: 9th grade conceptual physics optics, waves, and circuits exam

Trimester exam time here at Woodberry.  Yes, trimester -- we give exams before Thanksgiving, the first week of March, and the last week of May.  It's wonderful to have so many opportunities to give long exams, because students prepare diligently for these, and take them very seriously.  An exam is the best teaching tool I can think of.

A colleague in the history department this morning noted how the freshmen seemed low-key and not stressed.  Great!  That's exactly the attitude that Alex (the other 9th grade teacher) and I were consciously attempting to instill.  

I believe in predictable yet challenging exams.  The exam is not a place for cuteness, tricks, or extra-hard "let's see if anyone can get this" questions.  But then, I believe the same way about regularly scheduled class tests.  Conceptual physics test and exam questions always consist of questions adapted from New York State Regents Exams.  I don't throw in an AP question to challenge the top students; nor do I put a section of gimmee recall questions in.  Problem sets and regular quizzes use exam-style questions, too.  Thus, the students know exactly the style and level of difficulty to expect.

We have given three tests this year so far.  All were cumulative -- no, Johnny, you may not just forget everything about lenses and mirrors after the first test.  If you could, why should I bother teaching to begin with?  Two tests were heavy on the multiple choice; the third was just open-response.  Students were required to correct everything they missed on each of the first three tests.    So when I described the exam format -- two hours in which to complete 20 open-response and 40 multiple choice questions -- no one panicked.  They themselves commented, "it's just like a long test, then."

So how to "review" for the exam?  Freshmen especially can be crazy-anal about exam review, trying to cram way too much information from a textbook, or trying to game the test by memorizing the problems they think might appear.  That's unhelpful.  It's my job to guide them to doing the right sorts of things to review.

I start by posting all of the facts we've covered this trimester.  Click the link to see the file I posted.  I don't encourage anyone to read the textbook.  Instead, all year I've handed out fact sheets consisting of subsets of the posted file.  In the runup to the exam, I encourage students to work until they can recall every one of these facts with ease.  That's productive studying.

Then, I hand out a review sheet consisting of test-style problems.  I give enormous incentive* for students to not only complete the sheet, not only to correct their mistakes, but to get their corrections RIGHT.  It's one thing to memorize pages of facts... it's another to practice applying those facts to test questions.  The review sheet provides the same practice questions to everyone so that they all can discuss their answers with classmates.

* including substantial extra credit -- for perfect corrections only -- and the opportunity to attend a nacho party.  The nacho party is the more effective incentive.

Sending out the single-file fact sheet worked wonders.  This morning as I wandered the dorms, I found more than half my students using the fact sheet to study somehow.  They were quizzing each other orally.  They were creating their own written quizzes.  They were looking up facts to do practice problems.  They were making notations on the fact sheet so they could ask me questions when I came by.  No one ever, ever used a textbook like this in all the years I've taught.  But because I condensed the material to ten pages in which every single word is relevant, the fact sheet became not just useful but indispensable.  

Feel free to use the fact sheet for your class.  Every question on the exam is based on one or several of these facts. 

And if you'd like to see or use my exam, please email me.  I'd be happy to share.


16 November 2013

Who cares why you got it wrong before... just do it right.

Regular readers know I'm a True Believer in test corrections.  What better way to cement a student's understanding than to have him write out an explanation for each problem he personally missed on a test.

I discovered a new difficulty with test corrections in a general-level class today, one that I had never really noticed before.  My class spent an inordinate amount of time asking me and each other what was wrong with their original response; as a result, what should have been simple corrections took them for friggin' ever.

Interestingly, I have never had this issue on multiple choice corrections.  My students, whatever the level, just justify the answers quickly, without trouble.  See, on multiple choice questions, the scantron simply marks the answer right or wrong; there's no ambiguity about what part of the original response isn't right.

I've not had this issue with AP-level students on their free response corrections, either.  That's because I've always asked very detailed, targeted additional questions on the corrections.  They focus on answering my new question... and that question more often than not leads directly to the right approach.

But today was the first day I have done in-class corrections on a general-level all-open-response test.  The problems on this test are too simple to make my AP approach of targeted additional questions to be useful. As they faced an incorrect test and a blank page, I had a parade of students asking "did you mark off for just the wrong units, or was the answer wrong, too?"  "Is it my diagram that's incorrect, or the explanation?"  "Would this have counted had I said..."


Note that no one was arguing that they should have earned more points, or debating my ability to grade consistently.  We're well over that issue.  No, these were earnest questions, motivated by the desire to get the correction right, the desire not to make the same mistake twice.

Nevertheless, the interminable focus on "why did I get it wrong" kept too many students from focusing on what I wanted them to -- namely, just doing the problem right.  Even as I kept asking students not to try to figure out their mistakes, but to start each question from scratch, they couldn't let go:  "But, just tell me real quick so I know, was this part of the answer right or wrong?"  Several students spent 20 minutes trying uselessly to find the source of a mistake, but then finished in only 3 minutes when I forcibly removed their original problem from them.

And therein lies the solution.  Next time I want students to correct their open-response questions, I'm not returning the original test at first.  Instead, they'll get a blank test with the questions they need to redo circled.  Once they do their corrections, THEN they can have their original test back.  Not only does this new approach solve for the "why did I get it wrong?" issue, but it provides even more incentive to work steadily without distraction.  After all, they can't see their test grade until they get the corrections right.  :-)

I'll let you know how this goes when I try it next trimester some time.


06 November 2013

Graphs and circuits

John and Corey plot brightness of a mini light bulb with a vernier light sensor vs. voltage of a variable power supply.  They get a parabola, as they predicted.
James and Andrew plot voltage vs. current using a constant resistance.  The current was actually in microamps... With 9th graders, I'll work on this distinction soon by telling them that 1 amp is a LOT of current.  After they finished, I asked them to draw a new line representing what they'd get if they used a smaller constant resistor.
I'm trying to teach my freshmen to predict what a graph looks like.  We are well used to using equations like V=IR and P=V2/R, identifying the constant value, and drawing arrows to show which quantities increase or decrease.  Now I want them to be able to sketch graphs.

With these types of equations, we're only going to get one of about four general graph shapes.  Although I don't describe them in words to my class, for you I'd call them a sloped line, a parabola, a hyperbola, or possibly a flat line.  You can see these, with my very simplistic description of how to know which one we're looking for, here.  

The day after I hand these out, we do an in-class circuits graphing exercise in which students are asked to predict what four different graphs would look like:

* voltage vs. current for constant resistance
* current vs. resistance for constant voltage
* brightness of a bulb vs. resistance at constant voltage
* brightness of a bulb vs. voltage at constant resistance

The beauty is, each of these experiments can be set up very easily in our laboratory.  I have "decade boxes" which allow you to dial any resistance you want, from 1 ohm to 100 kilo-ohms.*  I have vernier light sensors, which measure brightness in lux.  

* careful... on the graphs that DON'T include the light bulb you have to use kilo-ohms rather than ohms so that the power dissipated by the resistance box doesn't exceed a quarter-watt.  Twice today a student accidentally turned the resistance box to zero, causing the resistor box to smell bad because it was starting to burn off the insulation.

In order to make this a relatively quick exercise, I provided a blank and scaled graph on the back page of each handout.  (Check the link above to see.  You may use these in your class.)  The key is, FIRST the students had to predict what the graph should look like; THEN, they had to do the experiment.  And sure enough, the graph looked like we expected.