There are millions of interesting experiments you can perform with your new Van de Graaff generator, but I will concentrate on the "hair raising" one. Have the lucky participant stand on top of an insulated surface (a Rubbermaid container top works well). It is critical for the person to be insulated from ground. If the charge cannot build up on the person, his/her hair will not stand up. Now, have the person put a hand on the sphere. Turn on the Van de Graaff generator and watch it go!
When the Van de Graaff generator starts charging, it transfers the charge to the person who is touching it. Since the person's hair follicles are getting charged to the same potential, they try to repel each other. This is why the hair actually stands up. It would not make a difference if the polarity of the Van de Graaff generator were reversed. As long as the person is insulated, the charge will build up (assuming, of course, that the hair is clean and dry).
My Van de Graaff generator will create sparks about 10 to 12 inches in length. I like to charge myself on it and point at the aluminum blinds on the window. The charge (electronic wind) will cause the blinds to move. I can do this from about 8 feet away with ease. Soap bubbles are also interesting to play with around the Van de Graaff generator. They initially are attracted to the Van de Graaff generator and float toward it; once they become charged by the Van de Graaff generator, they float away due to repulsion. There are multitudes of fun things you can do with your Van de Graaff generator. Use your imagination!
For more information, check out the links below!