Expert: Steve Nelson - 10/6/2009

Question
Hello again! Im sorry to admit this - even to myself - but that science fair project you gave me before was just too hard for me. Do you have any cool and interesting ideas for experiments that involve physics? I need something that can be easily formatted in an "If, then" hypothesis statement. For example:

"If the moon blocks cosmic rays when it is in the new moon stage, then when the moon is full it should reflect more cosmic rays than at any other phase."

That was a perfect hypothesis, but as Ive said, Ive found building the ion chambers to detect cosmic rays much too difficult. Do you have any other ideas? I need a complete plan by tomorrow, and you are literally my last life line. Thank you!

Answer
Well it's going to have to be drastically simplified at this point, because my other project was also aimed at high school students since that's what you wanted.  I do have another idea, about a simple but fascinating device you can build called a Kelvin Thunderstorm.  It uses simple droplets of water to create high voltage.  Here are some references on how to build it, but you can improvise.  I find plastic coathangers to be excellent pre-made insulators for this project, and I've built many variants out of nothing but aluminum foil, styrofoam cups, and a little tube, maybe some fishing line.  I can help you with the construction details later if you want, but just read here:

http://www.newphys.se/fnysik/3_1/kelvin/index.html
The instructable on it is here, but not as helpful:
http://www.instructables.com/id/Kelvin_s-Thunderstorm---Create-lightning-from-wa...
And a youtube video or two (second one is shorter but more dramatic):
http://www.youtube.com/watch?v=oY1eyLEo8_A
http://www.youtube.com/watch?v=3b23umXzPVA&feature=related
There's also a wikipedia page on it.

The thing is, if you play with it a while and you get it really sparking between the two closest contacts from far apart you can start testing things.  You can get the voltage so high that the electrostatic repulsion will start steering the drops away from the buckets at the bottom, it's really amazing how you can build high-voltage (low charge, so the safety forms should be no problem) out of just drops of water.  There are many possible hypotheses in if/then formats.  You can predict that adding soap to the water will destroy its surface tension, keeping it from breaking up into droplets and stop the generator from working.  You can predict that adding salt to the water will increase its electrical conductivity and decrease the average charging time to spark-down.  You can predict that oil won't work, being non-conductive.  You could predict that a more dense liquid (like really heavy salt water) could fall against more static repulsion and produce higher voltage.  You could say "if I make the dropper holes smaller and use more but smaller drops, the charge-up will be faster."  You could predict that covering the charge-inducing cans with something insulating (like a really good layer of plastic wrap) would keep any water from building up on them and help the device operate in a more stable state.  Remember to insulate the catching buckets and the inducing cans really well, it's key to the operation.  Styrofoam structures work great.  You could also predict something about water temperature, cold water gives off less water vapor and the device would probably work way better with ice water than with near-boiling water because of the leakage current from the water vapor of the hot water.

Good luck.  This really is a good project.  I'd build one that just has a bucket on top that you dump a set amount of liquid in every time that will cause at least 2-3 sparks.  They don't let liquid in science fair displays, but you can still bring the device and tell the judges that if you just poured some water in you could make it work.  Remember, it's all based on "like charges repel, opposite charges attract."