Apr 1, 2007
Water-powered mp3 Player
UPDATE: 31st March 2011 In hard times, humour is often all we have to lift our spirits. Given the current situation in Japan regarding the state of their nuclear power stations following the tragic and devastating earthquake and tsunami, a twitter follower, Christophe Shiffert thought this electric sweet potato funny enough to tweet about it and to allude to the constantly unfolding tragedy that is humanity’s failure to address the problem of energy in more creative and sustainable ways.
In this week’s video, MIT’s Walter Lewin demonstrates how to produce 10 to 15000 volts of electricity using a couple of empty paint cans, a bucket of water, some wire, and two balls. The question is how does this work and could you use it like the potato powered mp3 player?
I’ll look forward to seeing your suggestions in the comments and will post a more detailed explanation the the answers tomorrow.
Brian,
Did you ever find an answer to this question?
I have seen this demonstration in several books, videos and websites. I have tried it once, but wasn’t able to get it to work. The explanation given for how it works is always the same and, as you point out, it doesn’t actually make sense. The experiment obviously works, but the explanation that is always presented for it is clearly faulty. At one point, I asked my father, who is a renowned physicist at Stanford University, about it. He didn’t know for sure, but suggested that possibly it works because of some instability that occurs when one or the other sets of connected cans becomes charged relative to the other. Once the sets of connected cans are oppositely charged, the drops falling through the bottomless cans into the cans at the bottom evidently have the effect of increasing the existing charges, positive or negative. This is not a very good description and is certainly not complete, but I believe it is at least more satisfactory than the standard one which is always given. I am not a physicist, and electrostatics is not my father’s specific field (he’s a solid state physicist), but that is the best I have been able to come up with so far.
What I cannot explain is that buckets C and D seem to have symmetric effects on them (my guess is that electrons are being pulled out of the paint cans by the polar water molecules, leaving the paint cans positive and buckets negative), so that if both buckets are, say, negative, why would sparks jump between them. Would they jump from C to D or D to C, and what would that mean, since in the symmetric system there is no way to distinguish between the 2? Moreover, if a conductor connects can A with bucket C and can B with bucket D, why doesn’t current simply flow along these wires? Has any analysis been posted yet that goes a bit more through the physics of the thing?
The demo is exploiting static electricity and I think that relies on the dripping effect to work…so probably not in the way you suggest, but perhaps two dripping hose pipes, eh?