Wow, what an energizing game! Many of you have probably seen in real life the round, metal device that the character in the game touches to make their hair stand on end, but you might not know that it’s called a Van de Graaff Generator (named after Doctor Robert Jemison Van de Graaff, the physicist who designed the device). So, you may have seen one before, and you might know its name, but “how does it work?” is the really interesting question.
You can see from the game (or from other pictures, or if you remember from seeing a Van de Graaff Generator before) that the device basically looks like a tall, round tube with a large, metal sphere sitting on top of it. Below, there is a picture of a Van de Graaff generator where we can see what's going on inside. On the inside, the generator is hollow, except for a large belt of silk (kind of like a large rubber band, except silk instead of rubber) stretched over two spinning pulleys. At the bottom of the pulleys, there’s a piece of metal which, when the machine is turned on and plugged in, has a lot of electrons on it (shown as blue minus signs in the picture because electrons have a negative charge). When the machine is on, the band spins around and rubs against this piece of metal at the bottom, taking away some of the electrons and carrying them up to the top pulley. At the top, there is another piece of metal that rubs against the band and it is connected to the large, metal sphere at the top of the generator. When this piece of metal rubs against the band, it takes the electrons away from it and gives them to the large, metal sphere. Then the band, with no electrons (shown by the red plus signs, because a lack of electrons is a positive charge) moves back down to the bottom to collect more electrons, and everything starts all over again. When you are dealing with a bunch of free electrons sitting on something, it is called static electricity, which is why this machine is sometimes called a static electricity generator.
(Image created by Jason Kirkby)
So that’s how the machine works, but why does your hair stand on end when you touch one of these Van de Graaff Generators? Well, the first thing you need to know about electricity is that “like charges repel”, and there are only two, opposite charges, positive and negative. This means that two things that are positive, or two things that are negative, will try to move as far away from each other as possible. So, if you have two electrons next to each other, both negative, they will spread out as far as they can. When you touch the large metal sphere on the Van de Graaff with all the electrons, the electrons spread all over the outside of your body, including all over your hair! Now that your hair has all these electrons, all of your hair is negative, and so is your head! Remember how I said that things with the same charge will spread out? Well, since your head is negative, and your hair is negative, your hair will stand up to try to get away from your head! And since each one of your hairs is negative, all your hairs will spread out to try to get away from each other! If you want to do some experiments of your own with static electricity at home, check out our Static Electricity Experiments page.
