Most people have seen a Van de Graaff generator before at a science centre or on TV. You know that it makes peoples' hair stand on end, but do you actually know how it works? A Van de Graaff generator pulls electrons from the Earth, moves them along a belt and stores them on the large sphere. These electrons repel each other and try to get as far away from each other as possible, spreading out on the surface of the sphere. The Earth has lots of room for electrons to spread out upon, so electrons will take any available path back to the ground. The grounding rod is a smaller sphere, attached by a wire to the Earth. It provides a convenient path for electrons to move to the ground. If we bring the grounding rod close enough to the large sphere, the electrons rip through the air molecules in order to jump onto the grounding rod, creating a spark and crackling noise. When a fluorescent light tube approaches the negatively charged generator, the electrons on the generator flow through the tube and the person holding it. Flowing electrons result in an electrical current, lighting up the light tube.
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Operating the Tutorial
Invented around , the Van de Graaff generator is a popular tool for teaching the principles of electrostatics. Others just call it "that thing that makes your hair stand on end. American physicist Robert J. Van de Graaff began developing the high-voltage electrostatic generator that bears his name around They started out relatively small and got much bigger; one made in measured 40 feet high and could generate 5 million volts! That generator now lives at the Museum of Science in Boston, Massachusetts.
Van de Graaff generator - the basics
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate electric charge on a hollow metal globe on the top of an insulated column, creating very high electric potentials. It produces very high voltage direct current DC electricity at low current levels. It was invented by American physicist Robert J. Van de Graaff in A tabletop version can produce on the order of , volts and can store enough energy to produce a visible spark. Small Van de Graaff machines are produced for entertainment, and for physics education to teach electrostatics ; larger ones are displayed in some science museums. The Van de Graaff generator was developed as a particle accelerator for physics research; its high potential is used to accelerate subatomic particles to great speeds in an evacuated tube. It was the most powerful type of accelerator of the s until the cyclotron was developed. Van de Graaff generators are still used as accelerators to generate energetic particle and X-ray beams for nuclear research and nuclear medicine. Particle-beam Van de Graaff accelerators are often used in a " tandem " configuration: first, negatively charged ions are injected at one end towards the high potential terminal, where they are accelerated by attractive force towards the terminal.
The Demonstration: The volunteer puts her hand on the metal ball and her hair stands on end. Quick Physics: The Van de Graaff generator works by static electricity, like shuffling your feet across the carpet and shocking yourself on the doorknob. The electrons move up the rubber band to the metal ball and into the person. The electrons repel each other, so they try to get as far away from each other as possible. The Details: A Van de Graaff generator is a device for making lots of static electricity. 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 , Volts of the same kind of charge.