How does a Van de Graaff generator work?

A Van de Graaff generator works by transferring electric charge to a metal dome using a moving belt.

A Van de Graaff generator is a device designed to create very high voltages. It consists of a large metal dome mounted on top of an insulated column. Inside the column, there is a moving belt made of an insulating material like rubber or silk. The belt runs over two rollers, one at the bottom and one at the top, driven by an electric motor.

At the bottom of the generator, there is a comb-like structure called a "corona discharge comb" or "charging comb." This comb is connected to a high-voltage power supply, which ionises the air around it, creating a stream of positive or negative charges. These charges are then transferred to the belt as it moves past the comb.

As the belt travels upwards, it carries the charges to the top of the generator, where another comb, known as the "discharge comb," is positioned near the belt. This comb is connected to the metal dome. When the charged belt passes by the discharge comb, the charges are transferred from the belt to the dome.

The process continues, and the dome accumulates more and more charge. Since like charges repel each other, the charges spread out evenly over the surface of the dome. This results in a very high voltage being built up on the dome, often reaching hundreds of thousands or even millions of volts.

The high voltage on the dome can create impressive electrical effects, such as sparks and the ability to make hair stand on end. The Van de Graaff generator is a fantastic tool for demonstrating principles of electrostatics and is often used in physics classrooms to illustrate concepts like electric fields, potential difference, and charge distribution.