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The *idea* is sound. The question is could you get the focal point right using say 500 people. What they have shown over and over though is getting a large group to focus their point of light is hard.

http://sci-toys.com/scitoys/scitoys/light/solar_hotdog_cooker.html

http://www.google.com/images?hl=en&q=solar+power+mirrors&um=1&ie=UTF-8&source=univ&ei=Cu__TPjCIZL2swOr8ZmwCw&sa=X&oi=image_result_group&ct=title&resnum=2&ved=0CDgQsAQwAQ&biw=1271&bih=746

If you made say a 30-40 ft mirror and bent it into a parabola then put anything in that point it would probably instantly catch fire/melt. With bunch of disconnected mirrors separately moving mirrors (which they even showed once). Not so much as they can not get the focal point right or hot enough.

Deciding I needed a PWM for a project, I wanted to build my own to learn about electronics...so I went to radio shack and bought their $79.99 Electronics Learning Lab.(this kit alone is HOURS of amusement and learning)...but what I learned quickly is that following the Mimms book was very wasteful...the explanations of what is happening is scant...the diagrams are great, but blinking leds and making buzzer noises just ISN'T practical to a freshman in High School(I've taught them Freshman computing and mentored them in many aspects of I.T.)...

Below are some sites I've come across searching for 'simple enough for a basic solderer' and with readily available components(strip parts out of busted old computer power supplies/vcrs/radios/etc)..

http://www.electronics-lab.com/projects/audio/023/index.html

something fun and useful...a 'hearing aid' =) ... the entire site is useful

http://www.aaroncake.net/circuits/

some things more complex...

http://sci-toys.com/index.html

fun and educational .. some real easy stuff...and some more challenging stuff...

Hope this post ranks high enough for you to find it.

There are a lot of simple passive circuits, but no one is impressed by the switch and lightbulb, or the 1000 variations using solar cells or LEDs.

So, It seems to me that as a physics teacher, your probably better off focusing on the analog side of things and sticking with simple R/C/L type circuits. That stuff is fairly basic and matches up with basic physics. It helps to have some calculus to understand capacitors and inductors, but I understood basically how capacitors and inductors worked, long before I took a formal calculus class. Any good teacher should be able to impart a basic knowledge, its like computing the distance/speed/acceleration without doing the calculus, you just give the students the final formulas and an explanation of how to work them. Making the parts may or may not save some money, but it imparts a hands on kind of knowledge that isn't often taught in school.

Some ideas,

• Butterworth filters- Do them in the audio range, all you need are a handful of capacitors and inductors, a shared audio source (PC, Radio, etc), a couple speakers. Bonus points if you make the inductors and capacitors in class using wire/tinfoil/paper towels etc.
• RLC resonators - Design them to be in the audio range, or slow enough to be optically interesting. These can be tricky, especially if your trying to actually drive a load (speaker instead of an inductor, lamp instead of resistor). It might be better to have a few pre-built amplifiers with bulbs or speakers that you use as the load. Also, ignore the majority of the math and just focus on the w=1/sqrt(LC). The mistakes are often times the most fun and the fact that the results can be changed by moving you hand over them adds to it.
• AM Crystal radios - These require a sensitive earphone. This site sells them, and has instructions for building radios with nothing else but the earphone and stuff every student should be able to find at home. Be prepared, the earphone is fairly expensive ($3.85 in quantities of 100). Since they are small they will probably walk off. The alternative is to build an amplifier and let them plug their radios into it.

The real problem is that the excitement level is going to be fairly limited, unless you add a BJT or FET. If you add those, the sky is the limit. Again the math can get pretty ugly, but running a BJT as a switch between saturation and cutoff is easy to understand and opens up the possibility of building simple and/or gates. From that you can build a bunch of digital stuff. Radio shack sold 100 packs of 2N2222 BJTs for just a few $ back when they sold such things. I'm sure you can find similar deals if you hunt around.

That said, again your probably better off sticking with the analog, the results tend to be more impressive due to the limited parts count. I would stay away from IC's. I don't think they are appropriate for a basic physics class as they are just black boxes. Plus, they can be expensive in the quantities you will need.

• Gates - Build simple and/or gates for voting machines, etc.
• Small signal amplifiers - You can build an amplifier that can drive a speaker with a single BJT (it just needs to be fairly beefy) and you need high impedance speakers. Again, bonus points if you build the speakers! This goes well with the crystal radio.
• Colpitts/Hartley Oscillators - Again you can build simple ones with just a single BJT, these can often drive small loads without an amplifier as well, and they won't die like the resonators.

Finally, if your making the components, its going to be very helpful to be able to measure their capacitance, resistance or inductance. An inexpensive meter can provide R/C measurements, and you can build circuits that a part can be dropped in, that counts frequency or measures inductance.

What about a simple FM radio? I found this project a lot of fun http://sci-toys.com/scitoys/scitoys/radio/three_penny/three_penny.html and after building it with my nephew is started a whole series of experiments and visits to Radio Shackk for them.

There's a chance that a magnetic monopole might allow static magnetic levitation (Earnshaw's Theorem)

http://sci-toys.com/scitoys/scitoys/magnets/pyrolytic_graphite.html

Everyone knows about diamagnetic levitation, but Earnshaw specifically doesnt apply to diamagnetic materials.

http://en.wikipedia.org/wiki/Earnshaw's_theorem

Here's some links:

A white LED's spectrum

A CFL's spectrum

Here's some links:

A white LED's spectrum

A CFL's spectrum

http://scitoys.com/

This web site is full of cool stuff you can build. Available in dead-trees versions if you prefer. Seriously, check this out; this site makes me want to start building things.

Example: build a home-made radio. He starts with a trivial radio with only two parts, then adds another part to improve it, then improves it again... eventually he has you rolling your own capacitors! Each step illustrates something cool. By the end you are building a crystal radio like the ones soldiers used to build during World War I.

steveha

http://scitoys.com/

This web site is full of cool stuff you can build. Available in dead-trees versions if you prefer. Seriously, check this out; this site makes me want to start building things.

Example: build a home-made radio. He starts with a trivial radio with only two parts, then adds another part to improve it, then improves it again... eventually he has you rolling your own capacitors! Each step illustrates something cool. By the end you are building a crystal radio like the ones soldiers used to build during World War I.

steveha

Liquid Mirror Telescope

Does it matter? Well, the first to build a working waverider aircraft was a Scottish amateur rocketry group. Story has it that when NASA and Boeing engineers saw footage of the vehicle flying, they were staring at the screen in sheer envy. They'd got no further than theory. We also all know the story of the New Zealander who has jet-propelled go-karts and his own low-cost cruise missile. And the Gauss Rifle linked to above didn't look too complex, either.

Although amateurs are very unlikely to be building supersonic or hypersonic spy planes in the near future, none of this looks so complex that it could not be done by other nations in comparable time. Don't think it won't happen - too many potential benefits. Variants will also inevitably be adopted by commercial space planes, as it's so much cheaper than using vanilla rocketry and should be much more reliable.

To me, the only question I think worth asking at this point is who will be there first? Lockheed-Martin, China or Rutan? (And after Lockheed's disastrous hovering shuttle replacement in the late 1990s, it's not wise to just assume they'll automatically win such a race.)

(As a side note: you can't play with liquid CO2, at least not on Earth. It's either solid or gas, coz you need about 5 atmospheres of pressure for it to be liquid.)

Dry ice is fun. If you buy a dewar from somewhere like Edmund or sometimes American Surplus And Science (amsci.com) you might be allowed to buy liquid nitrogen from a local welding supply place. There are scads of online instructions for making instant ice cream with liquid nitrogen. If you're *really* careful, there are lots of other fun things to do with it: blow up balloons and press them flat as pancakes in the LN2, then sail one like a frisbee and, if you do it right, it'll warm up and pop back into an inflated balloon in the air.

I used to work at the Litle Shop Of Physics and they have lots of suggestions about silly projects you can do, that illustrate basic science, or weird science. A lot of them use things like 2L bottles with aluminum foil wrapped around them, filled with salt water, as Leyden jars, charged by putting aluminum foil on TV screens -- you can get 30,000 volts from that and load up 50 Leyden jars and have a big chunk of power for some exciting projects.

Scitoys has lots of neat projects. I built a set of Franklin's Bells (Ben Franklin invented them to warn of oncoming lightning storms) that are functionally identical to the scitoys version (tho' I'd thought it up on my own) and that's a quick, funny project. Actually, looking around on their site, you could spend the rest of your life just building and playing with what they have. I think someone wrote a book called Gonzo Gizmos that's based on what they've done, and it's fantastic. The audio-via-laser-pointer is really easy to set up (hint: use the smallest solar cell you can find or a photodetector that the laser pointer beam nearly entirely covers, to get a better signal/noise ratio) and a lot of fun to play with.

You'll notice I'm not talking much about chemistry. There's some superb stuff to do there (speaking as a person with a degree in chemistry) but it is, simply, more dangerous, and it behooves you to know what you're doing before you let your kids do stuff. My dad made seriously dangerous stuff, like stuff that left pieces of copper embedded in some of his friends' internal organs, and while that's great fun and all, wait until your kids are a couple years older.

Did I mention how much fun you can have with microwaves? Particularly if you don't care about them very much? Neon bulbs are cheap. Put some in the microwave and turn it on. Microwave CD's. Microwave marshmallow peeps. Have grape races. Butterfly a grape to form a dipole antenna and watch it vaporize. You can even melt silver in a microwave (tho' I have yet to actually try this.)

(As a side note: you can't play with liquid CO2, at least not on Earth. It's either solid or gas, coz you need about 5 atmospheres of pressure for it to be liquid.)

Dry ice is fun. If you buy a dewar from somewhere like Edmund or sometimes American Surplus And Science (amsci.com) you might be allowed to buy liquid nitrogen from a local welding supply place. There are scads of online instructions for making instant ice cream with liquid nitrogen. If you're *really* careful, there are lots of other fun things to do with it: blow up balloons and press them flat as pancakes in the LN2, then sail one like a frisbee and, if you do it right, it'll warm up and pop back into an inflated balloon in the air.

I used to work at the Litle Shop Of Physics and they have lots of suggestions about silly projects you can do, that illustrate basic science, or weird science. A lot of them use things like 2L bottles with aluminum foil wrapped around them, filled with salt water, as Leyden jars, charged by putting aluminum foil on TV screens -- you can get 30,000 volts from that and load up 50 Leyden jars and have a big chunk of power for some exciting projects.

Scitoys has lots of neat projects. I built a set of Franklin's Bells (Ben Franklin invented them to warn of oncoming lightning storms) that are functionally identical to the scitoys version (tho' I'd thought it up on my own) and that's a quick, funny project. Actually, looking around on their site, you could spend the rest of your life just building and playing with what they have. I think someone wrote a book called Gonzo Gizmos that's based on what they've done, and it's fantastic. The audio-via-laser-pointer is really easy to set up (hint: use the smallest solar cell you can find or a photodetector that the laser pointer beam nearly entirely covers, to get a better signal/noise ratio) and a lot of fun to play with.

You'll notice I'm not talking much about chemistry. There's some superb stuff to do there (speaking as a person with a degree in chemistry) but it is, simply, more dangerous, and it behooves you to know what you're doing before you let your kids do stuff. My dad made seriously dangerous stuff, like stuff that left pieces of copper embedded in some of his friends' internal organs, and while that's great fun and all, wait until your kids are a couple years older.

Did I mention how much fun you can have with microwaves? Particularly if you don't care about them very much? Neon bulbs are cheap. Put some in the microwave and turn it on. Microwave CD's. Microwave marshmallow peeps. Have grape races. Butterfly a grape to form a dipole antenna and watch it vaporize. You can even melt silver in a microwave (tho' I have yet to actually try this.)

This Free Space Laser Data Transmitter is just a toy, but it's partly what you're looking for. With two, you could make a full duplex two-way link over which you could run PPP. Paired with a more powerful laser (Thinkgeek green laser pointer maybe?) you probably wouldn't suffer too badly from signal loss. However, you can run the link as fast as the serial port will allow (a measly 112k?). I'm sure someone familiar with computer interfaces could hack a faster interface onto it.

You need something like this then... although it's not really suited for anything other than hotdogs. http://sci-toys.com/scitoys/scitoys/light/solar_ho tdog_cooker.html

There are plenty of designs available for nice solar ovens & fryers.. anything collapsible is usually a little more work, but worth the effort.

Probably not. If you look it up polyethylene glycol is a "stabilizer/thickener" and relatively inert. ITs function in spinal injuries is to , in effect, coat the injured nerves in a way that prevents some unhelpful things ["glutamate cascade"? in the case of strokes] that the body does for injured nerve tissue...its effect may almost be mechanical more than biochemical.

They also have a nice selection of other interesting projects...