There is a grounded comb close to the belt in front of the lower pulley, and another inside the terminal, close to the belt in front of the upper pulley, connected to the terminal. Rolling friction between the belt and the lower pulley charges the pulley, and it attracts opposite charges to the outer surface of the belt from the grounded comb. The belt then transports these charges to the terminal, where they are collected by the upper comb and transferred to the terminal. The shielding provided by the terminal allows the continuation of the process even if the terminal is already strongly charged. The high speed of the belt, along with the large discharge electrode, allows the continuous buildup of charges and great voltages to be achieved.
Some scientific laboratories have such generators several stories high.
They can develop sparks that go all the way across the room. But still that doesn't compare to the power of lightning, which can be several miles long. Demonstrating static power Besides being able to create fairly large sparks, these static electricity generators can be used for other experiments. When a person puts his or her hand on the globe of the Van de Graaf generator, the person's hair will stand on end. This is because the static charges collect on the hair and like charge repel, thus repelling the hairs fro each other.