# COMMUNITY : FORUMS : OFFBEAT

## what can i prove with this?

picking a topic for science fair has been hard. i was wondering what i could prove with a van de graaf generator. somthing i can test with it. any ideas?

sort by: active | newest | oldest
 1-10 of 20 Next »
Kiteman10 years ago
Not for free, but it's still a useful approximation. For your experiment, the input variable would be the diameter of the dome, output would be the length of the spark produced. That could be related to voltage afterwards in your evaluation.
guyfrom7up10 years ago
you prove static electricity
10 years ago
static electricity is anything but static though :-)
10 years ago
That's it! You prove that static electricity is not really static, it's really high voltage DC.
Kiteman10 years ago
Around 5-10kV, depending on air pressure, humidity and my memory. I'll google a bit.
10 years ago
Oh! This high-voltage wiki says it's 30kV per cm!
its a lion10 years ago
good question. make it and see.
10 years ago
That is, make one VdG with interchangeable domes of varying diameters.
westfw10 years ago
(you're repeating yourself.) An isolated sphere acts as a capacitor, and there's a nice formula for figuring out the capacitance. Bigger capacitors make bigger sparks, but less frequently for a given power source (belt, pulley materials, motor/etc.) I don't know if that would make a good subject for experimentation. Aside from being closely related to something you can just look up, making the sphere on the VdG is one of the harder parts of construction (Hmm. You could do a bunch of non-spherical "spheres" and see how they perform...) Another interesting idea would be to add a capacitor to your setup and see how different dielectric materials behave... (Don't get carried away. Even "small" capacitors can get quite painful when charged to VdG voltages.)
whatsisface10 years ago
Control can be the materials the brush and belt are made from, and variable can be the voltage of the motor you use. Just a suggestion.
 1-10 of 20 Next »