Time to have some fun with electricity. But first before we begin, lets take down some notes to cover the basics.
A Van de Graaff generator is a device for making lots of static electricity. Static electricity is made from extra charges stored some place so that they can’t move. Normally charges don’t like to collect in one place. They like to find opposite charges as partners and run away from particles with the same charge. The Van de Graaff generator used in the demonstration can store up to about 200,000 Volts of the same kind of charge. Compared to the normal house voltage (about 240 Volts) that’s a lot!
The generator makes static electricity the same way you do when you rub your feet on the carpet and then touch a doorknob. Inside the generator is a giant rubber band that rubs across a piece of felt, stealing its electrons. The rubber band then spins around and the electrons travel up to the big metal ball on top. If you have a hand on the metal ball, the electrons will go into you.
Generally, the stored charges on the Van de Graaff generator want to try to get into the ground. The earth is very big and the negatively charged particles (electrons) can get very far away from each other. If a metal ball, which is connected to the ground if brought near the generator, the charges will jump through the air from the generator to the ball.
If you touch the generator, all that electricity will go through your body giving you a big shock. It can actually be dangerous. You can be protected from the ground by standing on a piece of rubber or plastic. We say plastic and rubber are insulators since charges can’t travel through them very easily. When you touch the generator now, the charges can’t get to the ground. You are now filled up with electrons. The electrons don’t like each other and are trying to get as far away from each other as possibly. Usually this makes your hair stand up because it is filled with electrons that are repelling each other.
Check out John Travoltage for a better idea of what causes static electricity
For rainy days
Typically Van de Graaff generators have a hard time on wet days as electricity can easily discharge to the moisture in the atmosphere. So here is a video to show you the larger effects.