Van de Graaf Generator Activities
Activity 1: Explain that the globe of the generator builds up excess electrons through conduction. The built electrons are repelling since they are like charges and we know that like charges repel so they are spread out as much as possible. The charges are spread out because the globe is a conductor, unlike electrons that are rubbed onto the balloon, which stay in the general area where you rub the balloon.
Activity 2: The electrons are in an excited state because of mutual repulsion, which means that they are looking for a place to go where the electron population is not so dense. Since the electrons are excited they will jump to anything that comes close to the generator globe, such as your hand, the desk, water droplets, or dust particles in the air. When the jump to these new locations they drop to a lower energy level and when they make this jump they release this energy in the form of light, heat, and sound. This is why we hear a crack and see a spark for the generator. The electrons can even jump through a glass tube like a fluorescent light bulb.
Activity 3: Demonstrate that the shocks do not hurt, and give anyone who wants a chance to get shocked.
Activity 4: If you put a pile of tin plates on the top of the generator’s globe, they will fly off one at a time. Since each of them will be picking up some of the excess charges the plates repel each other and they will fly off one at a time.
Activity 5: A piece of tinsel or Christmas tree icicles will first be attracted to the globe by induction, just like when you stick a charged balloon to the wall, and then repel away from the generator after it picks up some excess charge.
Activity 6: If you start with your hands on the globe and then turn the generator on you won’t get a shock, because the charge doesn’t get a chance to build up. The charge will continually leak into you and then through you to the ground. This is why you cannot have a “Bad Hair day” while standing...