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Science Fair | ||
I started entering science fairs around the 7th grade, and never missed a year. This is a little chronicle of the projects I put together. I was always aghast at the many projects copied from the World Book Encyclopedia, so I always tried to think up something unique.
My first project was in the 8th grade, making an "emergency" crystal radio out of ordinary household items. Well, except for the diode and the capacitor . . and the soldering iron you need to assemble it. OK, so it wasn't that ordinary, but I needed a gimmick. In the 9th grade, I did the dreaded "Effect of Music on Plants" project with a friend. Needless to say, neither we nor the 4 other people who did that same experiment won anything that year, and the six tomato plants wound up dying in the name of scientific progress.
In the 10th grade, I had access to an audio tone generator, so I got the idea of testing hearing. I built a big booth and lined it with foam. Technically, it worked really well, but the booth was really hot, even with just a person and a 60 watt light bulb. I found some interesting curves in the frequency response of hearing for people of various ages, but pretty much what you'd expect. When you're young, its great. When you get older, the high end drops off. Some people had unusual dips and sensitivities though. I'll bet that drives audio engineers nuts.
In the 11th grade, a member of the local Astronomy club told me about a "floating plate" demonstration he'd seen as a kid at the world's fair. The plate was a demonstration of "futuristic" cooking methods. The aluminum plate floated in an alternating magnetic field, an consequently got very hot. I had to do some research to find out that the currents induced in the plate are called eddy currents, and I had to do a lot of calculating and guessing to figure out the magnetic field that would be required to float an aluminum plate. I had to figure out the self inductance of the individual coils, plus the mutual inductance of the system to figure out how much wire to use to ensure that it wouldn't draw too much current.
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| select the photo for a larger image of the floating plate in action. |
It would have been best to use 3/8" or 1/2" thick plate, but all I could afford was 3/16", and that cost me something like $70 because I had to buy a 1x6 foot sheet. I also had to wind the coils by hand, since I couldn't find anything nearly as big as I needed. I used the laminated core from an old burned out welder as my core material. I wound 4 outer coils of my own, and cut the top off a mercury vapor light ballast transformer and used that as my center coil.
I built a control box that would allow me to run the coils off 110v or 220v. Construction took a long time, but somehow, it basically worked. The plate didn't get very high, and it would fall out of the field if the coils weren't aligned just right, but it worked. It turned out that the magnetic interaction of the coils was too strong for 220v. Even though each coil weighed about 10 pounds, they would knock each other over at 220v, and I didn't have the time or skill required to make something that would hold them down and still allow the fine adjustment required to get the alignment right to contain the plate. I'd also planned to immerse the coils in an oil bath to keep them cool, but that also proved to be just too difficult and messy, so I settled instead on operating it for only 20-30 seconds at a time. The thing drew about 13 amps with all the coils powered up, and I blew a circuit breaker at the science fair.
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| Select the photo above to see a short movie of the inspiration for the floating plate in action |
Oddly enough, some 25 years later when I was watching a TV show (I think it was a Modern Marvels episode) about home appliances - there was the floating plate demonstration from the World's Fair shown in an bit of stock footage near the end of the show. That was an amazing bit of closure after all these years. I'm not sure which fair it was, but probably the 1933 Chicago Fair, because I remember him telling me about the light from Arcturus being used to open the fair - and that happened at the 1933 Chicago World's Fair.
In 12th grade, I had access to a computer and I wanted to use that somehow, and I was interested in astronomy, so I decided to use photographs of sunspots to see if I could confirm the sun's differential rotation speed. I took photos each day for several weeks and tracked some nice sized sunspots across the face of the sun. This project turned out to be a lot harder than I originally thought, because it wasn't until I started measuring the photos (with a microscope micrometer) that I realized I didn't have a reference point for a pole or equator or anything else to register the sequence of photos. I could place each sunspot precisely on a disk, but since the camera wasn't oriented precisely the same way each time, and the photos weren't taken at the same time of day, there was no way to register one photo with another. So I had to write some additional software to rotate each day's arbitrarily oriented disk until the sunspots formed the best possible line, then interpolated the sun's rotation speed based on the measured changes. This got me within about 10% of the right answer.
Below are a few examples of the kind of photos I used, taken at the prime focus of a 6" Newtonian using one of the Roger Tuthill solar filters that were very popular at the time. I used B&W film for the project, but included these photos taken on Kodachrome just for effect.
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| Sunspots captured on Kodachrome - click to enlarge | ||
I made it to the regional science fair all three years of high school, and won some place each time, but I never made it to the big one - the national science fair. All in all, it was a great experience though.
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