They each stood on an insulated platform and put their hand on the high voltage terminal so that they could be charged to as much as 250,000 volts.
The current is tiny so it is safe.
When they asked, "Will I be shocked?"
My reply was usually that they may shocked in the sense they would be surprised but wouldn't feel an electric shock with this experiment unless they wanted to.
As the charge accumulated each hair was repelled from every other just like the foils in an electroscope like this one that Ben Franklin would have recognized.
Here the electroscope is in operation.
A negatively charged balloon causes the foils to deflect as as electrons are repelled from the top bead even without contact.
In the last part of the video the electroscope has been charged so the foils are separated and come together when a finger touches the bead giving them a path to ground.
Here are some of the students illustrating the same effect
We gave each of them a mirror so they could see what they looked like when they were charged.
The only sensation they reported was the slightly prickly sensation as the hairs on arms and hands were repelled and moved.
If they and a friend wanted to feel a little electricity we would turn off the generator, wait a moment for some of the charge to bleed off, and then have them touch their friend's hand.
They would each feel a small shock as a spark jumped between them.
They wondered what my impersonation of an electroscope would look like.
We put a stack of aluminum foil pans on the terminal and they were repelled and tossed into the air as the charge built up.
Note the expressions.
This is a video of what that experiment was like.
We also had a set of Franklin's Bells.
Here the bell closest to the Van de Graaff is charged without any contact with the terminal.
Corona discharge from the sharp edges of the aluminum foil to the terminal is all it takes.
The bell attracts the blue bob which swings toward it.
As soon as it makes contact the bell and bob have the same charge so the bob is repelled and swings toward the other bell.
When it touches it shares its charge with that bell and now both of them have the same charge so the bob is repelled from there.
The bob having lost much of it's charge it can be attracted to the first bell again and the process repeats.
Even after the Van de Graaff is turned off the process continues.
Its terminal is still at high voltage until the charge leaks away.
Here is another demonstration of corona discharge.
The high voltage and sharp points cause a discharge that ionizes the air nearby.
The reaction as that air is repelled pushes back on the points causing the pinwheel to spin.
The kids had a chance to see what electricity feels like too.
They ask "Will it hurt?"
My usual reply is "You won't be damaged ... but it will feel like you are being damaged!"
Here the expressions are mostly those of anticipation though the last one is clearly after the discharge.
Here is a video of some of them taking on the Van de Graaff mano-a-mano in a manner of speaking.
I like the variety of reactions especially the ones who seem to be communing with it and others who are truly shocked by the experience.
Yes, balloons charged with static electricity will stick to objects that have an opposite charge.
Another device you may consider unlikely.
It is a motor made from some pop bottles and aluminum foil and powered by electricity traveling through the air.
Construction is simple, bottle (1) on one end is charged by corona discharge from a piece of aluminum foil attached to it and pointed toward the Van de Graaff.
The bottle (3) on the other end discharges current that reaches it through a similar bit of foil pointed away.
Between them is another bottle (2) that is free to turn and has vertical stripes of foil on it.
The stripes are charged by corona from yet another foil electrode attached to bottle 1.
The stripe takes on the same charge and so is repelled and moves away, another takes its place, and the process repeats.
Charge is removed from the stripes at the other end by another piece of foil attached to bottle 3.
To be clear, none of the aluminum foil electrodes touch anything other than the air and yet there is enough power for the motor to spin nicely.
Here the kids were proving that static (which means not moving) electricity moves very well indeed.
They were standing in a line, linked by small florescent bulbs.
The one closest to the Van de Graaff was holding a metal bowl that served as the connection to it.
When the Van de Graaff was started and the bowl was in contact with the terminal the electricity flowed through the chain and didn't have the chance to build up very much.
The bulbs lit all the way down the line and they felt the current but it was bearable.
The student holding the bowl was in charge (pun intended) of the situation though.
If he moved it away from the terminal charge built up until it was large enough to jump the gap.
At that point the accumulated charge passed through the line all at once, the bulbs all flashed and everyone felt more of a shock.
It takes approximately 25,000 volts to jump 1 inch (2.54 centimeters) so you can estimate the voltage they are feeling.
We turned off the lights for part of this so you could see the bulbs lighting.
They proved their bravery, had fun, and learned some science and history.
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