Van de Graaff Graphite

One day when we were getting the Van de Graaff generator out for some static electricity demos, one of my colleagues shared one of the coolest things I've seen. Rather than discharge the voltage build up through a finger or knuckle, he had students draw pictures on notecards using standard graphite pencils and held them up to the generator to create a path to ground through the graphite. The result is an impressive spark (larger build up with the greater gap) that followed the path drawn.

To try this out, I drew a simple lightning bolt zig zag on a piece of paper. Holding one end of the drawing firmly with my thumb, I then held up the other end of the graphite line while charging up the Van de Graaff. The result can be seen in the video that my colleague and I captured below. I think we should refer to this as "Van de Graaff-ite" ;)

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If you capture it in slow-mo you can get pretty impressive frames showing exactly how the discharge is following the graphite! It's basically instantaneous and while you can see it in real time, there is just something special about seeing the path that electricity is taking

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Troubleshooting

In my experience (and hearing from others who have tried) this demo doesn't always work on the first go. I am limited to the experience that I have with our equipment but here are the troubleshooting steps that are worth trying

• Lots of Charge - you have to get a really good build up of charge to jump that large of a gap to ground. The drier and more powerful the Van de Graaff the better :)
• Good Grounding - make sure that you are well grounded. Sometimes I have found that taking off my shoes or touching something like a sink with another part of my body works well.
• Fresh Graphite - I don't really understand this one very well but I've noticed that sometimes drawings can get "used up" and you may need to continually create fresh graphite drawings
• Alligator Clips - it's a pretty substantial shock if you hold it with your thumb. If you aren't interested in the that sensation, you can just ground it through an alligator clip connected directly to the graphite drawing. I couldn't get it to spark quite as dramatically with clip. I'm guessing that it just had to build up more charge before jumping to my hand.
  

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Disclaimer

As with any Van de Graaff generator demonstration, it is important to understand the safety considerations. There are some great resources through Flinn and IOP.

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Iterations

One of my favorite parts about Twitter is how easy it is to share and "remix" an idea. After sharing the video posted above several months ago, several other teacher have tried this out and put their own spin on the concept. Some of my favorites are included below:

Kids LOVED this today: thanks Joe. Their variations included testing which of 2 lines the spark will follow, varying the paper, and wetting the paper. Suboptimal photos though□.
And we did the electric wind (tape paper clip to VDG, hold up candle) from @BarnettDreyfuss! Fun day. pic.twitter.com/hZ9nwBAfYf

— Elissa Dunn Levy (@elissadunnlevy) March 7, 2023

This is so fun! I tried it with a pikachu pen drawing to add some flare! The current avoids the pen lines and jumped over the paper towards the bottom too so I think spacing out the drawing is important too. pic.twitter.com/fZJoItFvkW

— Andy Su (he/him) (@changandysu) January 26, 2023

I decided to take Joe Cossette’s idea for directing the Van de Graaff discharge using graphite on paper, but I added an LED light bulb. Hard to hold that bulb still when you are getting shocked, but it looks cool. pic.twitter.com/nbdOse5GWB

— Darek Dewey (@DarekDewey) January 24, 2023

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