What’s happening? From Vancouver’s Science World:
“A Van de Graaff generator pulls electrons from the Earth, moves them along a belt and stores them on the large sphere. These electrons repel each other and try to get as far away from each other as possible, spreading out on the surface of the sphere. The Earth has lots of room for electrons to spread out upon, so electrons will take any available path back to the ground.
“The grounding rod is a smaller sphere, attached by a wire to the Earth. It provides a convenient path for electrons to move to the ground. If we bring the grounding rod close enough to the large sphere, the electrons rip through the air molecules in order to jump onto the grounding rod, creating a spark and crackling noise…”
“When a student puts a hand on the sphere, the electrons will spread out onto that person as they repel from the other electrons. They are most obvious in a person’s hair because the like charges of the electrons repel each other and cause the hairs to stand up and spread away from each other. As long as the person is standing on an insulated platform, the electrons will not be able to travel down to the ground and their hair will remain standing up.”
Related videos include:
• The Museum of Science and Energy’s Van de Graaff Generator
• ExpeRimental: How to Make Static Magic
• The science of static electricity
• The Electric Sausage: A static electricity demonstration
Visually related: How do you wash long hair in space?