PTSOS3 Book of Phyz resources

The topics addressed in PTSOS3 are electricity, magnetism, and light. And, of course, mechanics. I distributed a big pack of physics love, including material from the following sections of The Book of Phyz.

1.08 Electricity (Physics 1)
1.09 Circuits (Physics 1)
1.10 Electromagnetism (Physics 1)
1.12 Light (Physics 1)
1.13 Wave Optics (Physics 1)
1.14 Mirrors and Lenses (Physics 1)

There are a few related items found in

2.07 Advanced Electricity (Physics 2)
2.08 Advanced Circuits (Physics 2)

There's also a link to the STAR Test/Physics CST released test questions in the margin to the right.

A rainbow of woo

It's always troubling to see a groovy physics phenomenon get hijacked by the purveyors of woo. Magnets have long been a favorite target of abduction. Homeopathic scam artists sell magnets to wear, to sleep on, walk on, and so on, all with the unfounded promise of "better health." Complete bogousity, of course.

Now it's the rainbow's turn. Not the rainbow, itself, but the colors of the rainbow. Announcing ColorEnergy. Arbitrary "powers" are assigned to each color...arbitrarily. If you give the purveyor a bunch of money, she'll explain the whole thing. None of it founded on research, of course. But like PT Barnum said, there's a fool born every minute. This scheme is just one more that parts the fools from their money.

I just don't like the rainbow being invoked to do the dirty work.

Thanks to The Amazing Randi for the heads-up.

Local teens find asteroids

When I was in high school, setting the high score on Asteroids required a lot of quarters, excellent hand-eye coordination, and good motor skills. A group of Cordova High School astronomy students took a different path. Instead of playing a video game, they discovered actual asteroids!

Two three-member teams in Glenn Reagan's Astronomy class discovered asteroids. Students Lycia Vang, Jisel Moore and Christine Sherer discovered two: KO7D84U and KO7D84W. Students Josh Rose, Mike Sebastien and Phillip DiJoseph discovered asteroid K07C54Q.

The Sacramento Bee has the full story.

Don't teach that right hand rule

Right hand rules in high school physics: is there a point? I'm in the midst of my electromagnetism unit, and there is much to learn, but also much to leave to future courses for students who wish to know more.

The former includes the right hand rule for determing the direction of the magnetic field around a current-carrying wire. This is a tough row to hoe, as it requires students to have a modicum of agility in thinking in three dimensions. My experience tells me that high school students have few opportunities to navigate the geometrical challenges of three-dimensional space. But the state of California wants its physics students to know this, so I teach it. I introduce it with a lab activity.

Among the things to leave to future physics coursework, I would include the current-field-force right hand rule. You know, the one involving the mutual perpendicularity of current, magnetic field, and magnetic force. Students are reeling from the 3-D demands of the first right hand rule. So why add this insult to their injury? What's the payoff? What gift does this knowledge bear that makes the pain of learning it worthwhile? In high school? Even the great state of California deems it non-essential.

Basic electromagnetism is rife with intangible fields and geomagnetic mayhem. There's some counter-intuitive stuff in this material. Can't we save this bit of trivia for another, later course?

Oh, and don't get me started on the left hand rule. (You really should click that link if you want a laugh.)

Excellent, flawed magnetizer

Do you use soft iron bar magnets in your classroom magnetism activities? Of course you do! Have you noticed their tendency to lose their field strength as time goes by? Such is the nature of soft iron. The fact that it can be easily magnetized makes it vulnerable to the loss of its field strength.

That's where a magnetizer comes in handy. I've got one that I use and am generally happy with. It's made by Electro-Technic Products (ETP), a company in Illinois. It's easy to use and works effectively.

There is one problem with it, though. One that American River College physics instructor, Ann Hanks, pointed out a few years ago.

The ETP magnetizer has its magnetic poles labeled backwards. The end of the magnet you place in the "north"-labeled receptacle will be magnetized south, and vice-versa.

Hanks pursued the matter and contacted the company. They were aware of the situation, but intended to maintain the errant labeling. ETP told Hanks that their customers complained when the "North" of their newly magnetized magnets failed to attract the north-seeking end of their classroom compasses. These customers wanted north to attract north.

ETP acquiesced and relabeled their magnetizer to match customer demand. "The customer is always right."

Well, except when they're wrong. If you get one for your classroom, you will need to relabel the pole indicators on the device before you use it. Sigh.

Released Test Questions: 7th-grade science

There is a great annual, intellectual sport of criticizing the released items on California's STAR test in physics. Each year, the California Department of Education releases 25% of the previous year's test. When the new items are published, the listservs light up with hue and cry: many (if not all) the items are deemed trivial, poorly constructed, or flat-out wrong. Or all of the above!

Some of the criticism is well-founded, some not so much. I doubt there is a question in existence that would be unanimously approved by a group of 100 physics instructors. Add to that the reservations that many teachers have regarding state-mandated science standards, and you've got a recipe for, well, enthusiastic criticism.

It is in that spirit that I present these questions from Illinois (Word document). The document appears to be one district's attempt to simulate a statewide assessment given to 7th-graders. The state's released test questions can be found here (PDF).

Please look at both and see if you think they constitute an assessment you would hope for in your fair state. How would you assess the writing, grammar, content, and difficulty of these items? Let me know in the comments.

Admonishment and acknowledgments to Freakonomics via Bad Astronomy. Those sites are portaying the school district's practice test as the state's assessment items. I fear they are in error to do so.

UPDATE: Here's an item from the official ISAT RTQs. I would have recommended rejection had it been offered for California's physics STAR test.

What property of light waves can be observed as light waves pass from one medium to another and change speed?
A Diffraction
B Refraction
C Reflection
D Separation

Seems straightforward enough. Why would I have rejected it?

Turn your classroom into a science museum...

for one day. After years of trying to set up groovy demos in my classroom every year for Open House, I decided I was working too hard. Why should I set up demos to impress visitors when I have 150+ students capable of doing the job for me?

So since 1994, that's exactly what I've done. We call it ExploratoRio ("eks-plor-uh-TOE-ree-oh)"), because it's modeled on San Francisco's Exploratorium but it takes place at Rio Americano High School.

The good news is that my students do a great job of researching, constructing, and exhibiting demonstrations. They explain their exhibits to elementary students who visit during Open House Day. Elementary students think high school students are gods. High school students know they're gods. So everyone's on the same page. Seriously though, our physics students enjoy teaching a mini science lesson to younger students. And the young scientists are amazed by the exhibits.

In the evening, parents of all the students attending the school are invited to the school's Open House. Our ExploratoRio is a huge hit--we aim to make it the grooviest destination at the school that night. It is a rare and determined parent who can wade into such a cacophonous carnival of kinetic energy to find the teacher and ask about Johnny's current grade. Physics professors from California State University, Sacramento often stop by to quiz our students about the physics behind the exhibits. Our students do very well under such scrutiny! And the professors have more hands-on physics fun than they're allowed to have at the university.

Many of those elementary students eventually end up in your physics class years later. The whole affair is a big promotion of your class to the school community.

The bad news? It's a nontrivial task to organize the event. Much more work than I did before 1994. Oh well.

I've posted a few pages and PDFs of resources you might want to check out if you want to have such an event at your school. It's a lot of work, but it engages your students in ways your class cannot. It promotes your class in the short and long term. Your administrators will have the opportunity to see the extent to which you walk on water. And it makes little kids happy.

You can find our ExploratoRio Resources here. And I'll keep a link off to the right for convenience. Click the photo above to see photo albums from some past ExploratoRios.

Time Fountain—have you seen this thing?

Wow! I found this little wonder while gearing up for ExploratoRio 07. But I'm going to shut up and let you watch the film now. Wow! I added it to the Web Video for the Classroom page.

ALERT: In good times, you should advertise...

in bad times, you must.

The time to advertise your physics course it now, colleagues. Counselors are heading out into classes to obtain student schedule requests. If you want to maintain or--better yet--increase your physics enrollment, don't keep your class a secret.

Physics is not (yet) a required course for high school graduation. You and I will likely be happier if it never becomes a required course. But that means nobody really needs to sign up for it. Yet physics is the grooviest course offered at your school, so everyone should be signing up for it.

You could visit the chemistry classes on your campus and do a dog and pony show, begging chem students to sign up for physics. I don't recommend that approach. It shows your willingness to accept the 1950's science pipeline: everyone takes biology, half proceed to chemistry, and half of them proceed to physics. No! Chemistry is not a prerequisite for physics.

In years past, I took the effort to mail out personalized letters to all chemistry students' parents, asking them to encourage their son or daughter to enroll in physics. The success was modest. And it buys in to the 50's enrollment model.

One year, I did something that seemed much less "personal," yet increased my enrollment from four sections to six. A 50% growth rate! How unsustainable is that, Al Bartlett?!

What did I do? I advertised! I used these flyers printed on fluorescent, "neon" paper: paper so bright you can see it in the next county. Astrobrights are nice, but fluorescent, coated paper (one side color, one side white.

The point is to let students know how cool the class is and that you want them to enroll. Sounds simple, but it works.

I would also recommend that if you have an Algebra 2 barricade blocking enrollment to your class, do what you can to remove it. It really doesn't need to be there. You can run a perfectly sound, standards-based physics course without an Algebra 2 prerequisite. Students need Algebra 1, to be sure. Geometry would nice (though not required). But they truly do not need Algebra 2.

Physics classes that sit behind prerequisite barricades of chemistry and Algebra 2 will succeed in keeping most high school students out of the best science course offered at your school: physics! So knock down the barriers. And advertise.

I will personally guarantee your results or double your money back.

Melted meter—what to do?

Analog meters. Very old-school, I know. But for teaching circuit concepts to students, I think they're great. Needle rides up and down like the one in a speedometer. Circuit physics is not very "naked-eye," so I think it's good to use a meter that has a familiar look and feel. Some teachers prefer digital meters and they have their reasons. To each his/her own.

I use DC voltmeters (0-10 V) and dual-range DC ammeters (0-1 A, 0-5 A), each one less than $20. In one lab, I have students connect each meter in series and in parallel in succession. They decide which is connection more useful for each meter. Series for the ammeter and parallel for the voltmeter, as fortune would have it.

Though the meters are, um, "inexpensive," they hold up pretty well under the conditions of the introductory laboratory. My students are generally very good about treating equipment well. And I do what I can to encourage that behavior.

But things do happen. The meter pictured above is an ammeter. (Click the image for a larger view.) It had been connected to a variable DC power supply in parallel to the circuit whose characteristics were to be measured. Using voltmeter test lead wires. In a lab whose instructions included, in ALL CAPS, the admonition that the test leads were to remain connected to the voltmeter at all times and were never to be connected to the ammeter.

This was our third lab using the ammeters, and the second one using the power supplies.

What to do about the students who melted the meter by not following instructions? What would you do?