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Jan 15

Lightning Experiments

 

Leaf before electrocution

Leaf after one electrocution

 

Leaf after 2 electrocutions

With two new students in class, we revived the Van de Graaff generator, because everyone wants to see and feel lightning. Students asked questions I thought would lead nowhere, like what happens to leaves near the base of a copper tube leaned against the generator? I guessed that the tube would ground itself and leave the leaf unaffected. No, the leaf, trapped under the edge of the tube danced violently. Then someone noticed very small gravel, not much larger than sand, hopping in the vicinity of the grounded end of the tube. Also, we electrocuted a leaf by putting it on top of the generator and then turning it on. Three photos show before and after 1 and 2 electrocutions. One student thought he could see differences, but I can’t tell. We’d need to do this more carefully to filter out expectations. Bouncing gravel led to a test of a pebble and leaf fragment to see how they jumped differently. Attracted to a hand connected to the copper tube, only the leaf fragment reacted. We recorded high-speed video, but it showed nothing, so I did not post it.

Feeling force of pie tins flying off Van de Graaff generator

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