I’ve got so many different posts that I want to write… scribbled notes on different science myths and beautiful everyday things, but I have been so very busy. I’m sorry. I will get back to writing detailed posts in a few weeks!

In the meantime, I’d like to recycle a good old post on making your own phonograph. If you’ve got some old records, try this one, it’s pretty astounding when it works!


phonographI love this little activity… Have an old record but no record player? Here’s how you can listen to it. Take a record and stick a pencil through the hole in the middle so it’s pretty close to the point of the pencil. That’s your turntable. Now take a piece of paper and roll it up into a loose cone and tape it. Flatten the pointy end a little and stick a pin through it. You may want to tape the pin to the end of the paper cone so it’s more stable. Now have a friend turn the record by slowly rotating the pencil. Place the pin, point down, on the groove of the record, and gently hold the cone so the pin stays in the groove of the record. Try to turn it at 33 1/3 times per minute — good luck! Here is a more detailed description of the activity.

Here is my post on my podcast where you can hear how it sounds and how to teach it.

You should hear the music playing, albeit a bit wobbly. The record has a groove in it — one long spiral. The needle vibrates in response to the shape of the groove. But the needle on its own doesn’t vibrate very much air. When it’s attached to the cone, it vibrates the cone, which can then vibrate more air, making the sound louder. The cone also directs the sound, making it easier to hear.

Today’s students often haven’t seen a record before, and so it can be useful to look at it under a microscope or magnifying glass to see the groove. Note that a CD is also sort of “carved” — it has microscopic pits in it. But instead of mechanical vibrations, the grooves in the CD are so tiny that it interacts with light. That’s why records wear out — the needle wears out the grooves. That’s not a problem with CD’s, since it’s just light touching the surface. Interestingly, it doesn’t matter (as much) if you scratch the side of the CD with the rainbows on it — but if you scratch the metal coating on the other side, the light won’t reflect from it correctly and you’ll spoil the CD.

Wikipedia has more information on phonographs, and so does this site from Arbor Scientific.

If you’re interested in making your own working phonograph (not just the pin and paper method) to actually record your voice using a plastic cup (replacing the old fashioned wax cylinder), check out this kit from Make Magazine. I hear they don’t carry the kit anymore, but someone Googled and found it by a company in Japan.

Here’s a video of it in action and here’s what it sounds like.

A teacher on a teacher listserv I’m on writes:

In my collection of Edison Phonographs I have many that will allow for purely mechanical reproduction of sound. I have an Edison tinfoil phonograph that records on tinfoil (duh) and numerous machines that record on wax cylinders. First the wax cylinder is shaved to a clean surface then a cutter head consisting of a diaphragm with a sapphire cutting stylus is lowered onto the record surface. As the cylinder turns, wax is cut by the stylus where the depth of the cut represents the wave pushing/pulling on the diaphragm. It is called the “hill and dale” or vertical cut type of recording.

The Gakken phonograph made in Japan uses a side by side motion or lateral recording. This is what the common 78 RPM records used from 1896 up through the mid-1950s. The toy phonograph does work but results vary depending on numerous factors. One is the temperature of the plastic cup used for the recording. I have found that a hair dryer warming the cup helps but one must be careful not to melt anything. The Gakken machine appears on eBay regularly under the search Edison Phonograph but shipping is as expensive as the machine is because it is air mailed from Japan. Maker Shed in the US carries it as well with some savings on postage but at a higher price.

tt_icon_170Despite my better judgment, I invite TI staff educator Eric Muller to do one more set of activities on my Teaching Tips podcast —several things you can do with soda straws.  Listen to the episode – The Last Straw.

Holding Charge activity (PDF)
More of Eric Muller’s activities

Hey hey, I’ve got a twofer in the current issue of the Physics Teacher!  One is my article on the chemistry behind the saltwater battery. The other is an article on blogs that physics teachers can use.  I’ll post the full blog article (the published one was cut quite heavily) a little later!circuit_th

Here’s the crux of the saltwater activity:  When you connect cups filled with salty water together, you can make a current strong enough to ring a buzzer or light an LED.  Neat!  This article explains the electrochemistry behind this popular activity so that physics teachers can know enough chemistry to understand a lot of the weird behavior that they see.  I’m a physicist, so I don’t know much chemistry.  So this paper is kind of neat in that it’s a joint venture between myself and my dad, retired physical chemist Dennis Chasteen.  My mentor Paul Doherty is also a co-author.

The construction of the cell is largely borrowed from the Exploratorium’s Square Wheels book (thanks to master tinkerer Don Rathjen!)

You can download a PDF of the article here.

Here are some supporting materials on my mentor and coauthor (Paul Doherty’s) website.

The NSDL has pulled together some classroom resources for teaching about voting and polls, voting technology, and the history of voting.  These are taken from the NSDL Expert Voices blog.

Annenberg/CPB: Cast Your Vote
From the NSDL Middle School Portal: Math and Science Pathways

Multiple polls claim to know how public opinion shifts day-to-day during political campaigns. This web site offers a ficticious look into an election campaign at the math behind the polls. Concepts such as random sampling, margin of error, confidence intervals, and ways in which surveys can go wrong are reviewed.

Majority Vote: What percentage does it take to win a vote?
From the NSDL Middle School Portal: Math and Science Pathways

Understanding national election results is complicated. This classroom activity helps students think carefully about how percentages are used mathematically to determine voting outcomes. The importance of understanding the meaning of percentages in media and marketing is also noted.

Voting Rights
From NSDL Teachers’ Domain: Digital Media Resources Pathway

The Fifteenth Amendment to the Constitution was passed that prohibited racial discrimination in voting was passed in 1870. The Voting Rights Act, however, was not signed into law until 1965. Find out what happened in the nearly one hundred years between 1870 and 1965 to ensure that everyone has the right to vote in this multimedia resource from Teacher’s Domain.

Election 2000: A Case Study in Human Factors and Design
From the NSDL Engineering Pathway: Engineering Education Resources

The goal in presenting this case based on controversies surrounding the November 2000 presidential election, specifically the difficulties encountered in interpreting imperfectly punched ballots, is to help college-level students recognize how engineering solutions can be brought to bear in solving problems of national importance.

Hey guess what!  Science Teaching Tips was just highlighted in the Websights section of The Physics Teacher.   Woo hoo!

I’ve got a new episode of  the podcast posted — The drama of the immune system. This is one of the favorites of our group at the Teacher Institute, and teachers are always asking Tory to do this little bit of theater.  In this classroom activity, staff educator Tory Brady shows you how to make the immune system into a bit of drama.  This is especially good for K-8 students, to help them understand the roles that each of the main characters in the immune system (macrophages, white blood cells) play.  Heck, I found it helpful to make all that vocabulary into a little story.  Much more memorable.  Enjoy!

I posted a new podcast – “Ooh you make my motor run” on my Science Teaching Tips podcast.  One of the Exploratorium staff educators, Modesto Tamez, tells how he gets students exploring electromagnets, a great preparation for making an electric motor.

Here’s the Stripped Down Motor activity: www.exploratorium.edu/snacks/stripped_down_motor.html