What happens to the size of a spark when the distance between a Van de Graaff generator and a grounding dome changes? What happens if they touch?
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Joanna and Steve: Just science!
Joanna: Hi! I'm Joanna!
Steve: And I'm Steve!
Joanna: And this is a Van de Graaff generator!
Steve: And this is called a grounding dome because it's attached to the earth through this wire.
Joanna: When we turn the Van de Graaff generator on electrons jump between the two domes, creating sparks!
Steve: When the domes are far apart, the sparks are fairly big, but there's a fair amount of time between each one. When the domes are closer, the sparks are smaller, but they happen sooner.
Joanna: That's because air is a fairly good insulator. When the domes are far apart, more electrons are needed to jump the gap. When the domes are close together, fewer electrons are needed before the spark forms. The fewer electrons that are needed, the less time it takes to build up. When the domes touch...
Joanna: Nothing happens. That because, to the electrons, the two domes are essentially one piece of metal. The electrons can flow between the two domes, through the grounding wire and into the ground without needing to build up.
Thanks for watching! I hope you'll join us again soon for another experiment!
Steve: Is it safe?
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