Sunday, May 03, 2015

Kinetic Karnival links updated

It seems MySpace (yes, it still exists) changed all the URLs to their extant content. I'd snark, but kicking MySpace at this point just seems merciless and unfair.

Jearl Walker's excellent Kinetic Karnival videos are warehoused there, so all the links I had to his page and videos went bad.

The original post highlighting his videos and my curriculum was this:
Jearl Walker's Kinetic Kanival

Down the rabbit hole: Well, the links to my question sheets were equally outdated. So I've updated them. The linked PDFs are not always the most current, but should be fully-functional and correct.

Happily, I've updated the links, so this post is once again operational, as is the link in the right margin of this blog.

If you see that something's gone awry, please let me know. I'll do my best to get things repaired ASAP.

Monday, April 20, 2015

Disassemble, Yes!

As a child of the ’80s, I saw Short Circuit more times than I can count. To this day whenever I take something apart I hear the terrified Number 5 yelling, "Disassemble?! No!!" as he realizes what it would mean for him. But I still take things apart, because it is fun.

There have been many things I've collected (okay, maybe call it hoarded) over the years for use in my classroom. Some I have specific and immediate uses for .... some not so much. I still have part of the framing from a holiday light lawn sculpture of a snowman that I just know will be perfect for something, someday.

I finally got the time this year to disassemble an old toaster, hair dryer and space heater. I reference these appliances when I teach electricity as a practical example of the conversion of electric energy to thermal energy. By the time we get to that, students have often had personal experience with that conversion when they leave their circuits on too long and touch hot resistors.

Even though we've talked about the dissipation of heat from electrical circuits I don't think my students believed me until they saw all those coils of wire. It was a simple thing to take them apart (they weren't working anyway) but many of my students were just in awe of seeing the inside of something. Little do they know they get to do it next week.

Now that our current electricity unit has come and gone we have moved on to electromagnetism. I have my students make a speaker out of paper using a paper template I made (pdf or google doc), a doughnut magnet and a coil of magnetic wire. Its a simple build based on Modesto Tamez's activity from the Exploratorium, but the students love it every year. It can be expanded by asking students to improve the design, increase the volume or efficiency. I've also seen a headphone project follow this for which students have to make their own working headphones based on this speaker design. (NGSS Science & Engineering Practice right there!)

This year I'm adding a "Dissecting Headphones" lab to my unit. Thanks to RAFT I scored a gross of cheap ear bud headphones several years ago that I've been holding on to (hoarding again). Each pair of students will get a set of headphones so that they each get to dissect one ear bud. The instructions go step by step for these particular headphones and lead students all the way to the small magnet and coil. I've done it with high school aged students before and despite building the paper speaker only a few minutes before, they are shocked—shocked—that their ear buds work the same way. They use classroom scissors and a straight pin; they can use wire cutters too, but they are not required.

Suddenly they all start making connections. "This is how a microphone works, too!" and "That's why my headphones attract paperclips!" are heard all over the room. And it's magical.

The lab my students will do this week includes both the "Make A Speaker" and "Dissecting Headphones" labs in one file available as a pdf or google doc.

Sunday, April 05, 2015

Canvas to Keynote conversion update

It began in October, 2012. Full story here.

At the outset, it looked like this.

In June, 2013, it looked like this.

Last year (April 2014), it looked like this.

Now (April 2015) it looks like this.

Progress. As sure as it is slow.

Sometimes demos go wrong—that doesn't make demos wrong

If you're hip enough to have tuned into this blog, you've probably seen the viral video of the cinder-block smash demo gone wrong. I'm not linking to it directly, because it's not any fun to watch. Of course, in this modern era, you can find versions of this incident from multiple angles.

I have mixed feelings about this demo and have never done it, myself. But I think Greg Schwanbeck makes a powerful argument against the knee-jerk reaction that will likely follow.

Please Don't Ban My … Physics Demos From Schools

And despite the date, this was no April Fool's joke.

Paly teacher burned in science experiment accident

Details are sketchy, so I'm not sure what conclusions can be drawn. No matter how often we've done some of these demos, it's imperative to remember the risk involved.

We wish speedy and full recoveries for both injured teachers.

And, OK; I'll give you a bed of nails blooper—direct from my talented and enthusiastic colleague, The Skeptical Teacher Matt Lowry. (Things get real at about 5:25.) He has recovered!

Tuesday, March 31, 2015

Van de Graaff Ping Pong

As played with a bundle of silk thread, as you do.

This gem comes to The Blog of Phyz from Inderkum's Jessica Downing, an upbeat, resourceful teacher at the most amazing high school in America.

It's a nice sequence of polarization, charging, repulsion, and discharging—rinse and repeat. It's like a puppy playing fetch.

This video below is slow-motion. This link will take you to the normal-speed version.

Van de Graaff Demo

Quantum locking

I guess I missed this one the first time around. Better late than never. I've seen magnetic levitation, but it didn't look like this.

Quantum Levitation

Uploaded on Oct 16, 2011
Video courtesy of the Association of Science-Technology Centers (ASTC), representing the science center and museum field worldwide. To learn more, visit Follow us on Twitter: @ScienceCenters.

Acoustic extinguisher

Low frequency sound douses a flame. I haven't seen a good explanation. In NGSSpeak, I'd say what we have here is engineering without a full scientific explanation. The explanation that, "it separates the oxygen from the fuel" is not working for me. Moving so much air that the temperature of the reactants is reduced below the combustion temperature seems more plausible.

Here's the article from Sputnik International

Pump Up the Bass to Douse a Blaze: Mason Students' Invention Fights Fires

Sunday, March 22, 2015

Electrophorus Engineering

One of the scariest parts of the Next Generation Science Standards (NGSS) are the Science & Engineering Practices. An easy way to slowly align your curriculum to NGSS is to modify a current demo, lesson or lab so that it is aligned with one of the Science & Engineering Practices. In a (brief) nutshell the Science & Engineering Practices are a skill set students should have in order to explore science phenomenon and engineer solutions to problems or fullfill a human need. Bozeman Science has a nice set of videos on the eight practices. The first one on Asking Questions & Defining Problems is helpful in understanding what NGSS considers the difference between Science & Engineering.

In the past I've created an electrophorus from a styrofoam cup and aluminum pie pan and used it to light a small neon bulb as part of my electrostatics lecture. Among The Exploratorium's many "snacks" is one called Charge and Carry that explains the traditional demonstration. Usually a styrofoam sheet is rubbed vigorously with a cloth to separate charge through friction. The electrophorus is set on the styrofoam and the charges in the aluminum pan polarize; by then touching the top of the aluminum pan you charge it by induction. If you pick it up by the insulating handle, touch one lead of a neon bulb to the aluminum while holding the other you can light a small neon bulb. You form a complete path of conducting material to the ground allowing charges to flow.

This year I did not show my students the electrophorus but asked students to experiment with different materials to explore the best way to light the neon bulb. Specifically students were working on the sixth practice "Constructing Explanations and Designing Solutions." Students had access to the following: plastic cups, plastic plates, paper cups, paper plates, styrofoam cups, styrofoam plates, aluminum plates, aluminum cups (made from rolled aluminum foil).

Students were given this image to understand the arrangement of their materials and instructions on how to charge and ground the electrophorus. Students were told to try different designs to light the neon bulb; each time they changed materials they were to record their results and try something else.

All groups eventually realized they had to use an aluminum plate to conduct the charge to the neon bulb. Most groups used a  styrofoam cup as the handle although some experimented with multiple stacked paper cups and reported a longer and brighter light from the neon bulb. Some groups tried rubbing the aluminum pan directly, skipping the styrofoam sheet, and reported even brighter lights.

After they optimize their design students were asked to write a conclusion paragraph: 
In an age appropriate paragraph explain (1) how the bulb can be lit this way and (2) justify your design choices and how well it worked. Be sure to discuss each of your designs and how their results influences later designs.  

As you might expect, results varied. Some groups really dove into it, referencing their book, asking me clarifying questions and constructed thorough explanations of what they were seeing. From others I could tell that students did not understand how the charge was initially separated, why a conductor was used for one part and an insulator for the other or how the static charge lit the bulb. By discussing their results the next day most students were able to correct their misconceptions. In the end I think they ended up with a much better understanding about the electrophorus and begin to see how current works than if I had just done it as a demo. 

Did it take longer? Yes. Was it worth it? Yes!

Electrophorus Build It Activity (PDF) (Google Doc)


This one's for you, imagineers!

What is Plastimake?

This is the kind of modeling I can get excited about!

The real world keeps taking away my real world physics

Once upon a time (a few years ago), a reasonable high school physics question was, "Why do the first broadcasters in a given television market get the lowest channel numbers on the dial?" In Sacramento, for example, that would be the NBC affiliate, KCRA, who got Channel 3. Channel 1 was never licensed to anyone by the FCC, and Channel 2 was given to the neighboring San Francisco market. The channel numbers correspond to broadcast frequencies: lower channel numbers broadcast on lower carrier frequencies. The corresponding longer waves are better at diffracting over hills and into valley, delivering commercial messages to more viewers.

But broadcast technology changed in 2009, so the problem is no longer relevant, as far as I know.

And now chromatic aberration? Researchers at Harvard have apparently developed a flat lens that focuses all colors at the same point.

Perfect colors, captured with one ultra-thin lens

Well, we'll always have The Dark Side of the Moon.