A band generator or vandegraaffgenerator is an electrostatic generator designed by Robert Van de Graaff in the early 20th century. The generator mainly consists of an insulating tube in which a hollow metal sphere is confirmed. Drawn up In the vertical, isolated tube running an electric insulated band that physical electric charge of under (by friction with the actuating shaft or submitted by a high-voltage unit) to above conveys. The band serves as a power source. Both above and below the cargo is transported by metal combs with sharp points. Under this on tape, and picked up again at the top of the globe. Also, at the bottom are static electrical charge on the band by the band brought along another suitable insulating material to rub – for example, a rubber band at the bottom about what wool or cat skin rubs (called the tribo-electric effect).
Essential in the vandegraaffgenerator is the fact that in the center of the loaded ball no electric field is present. All by the band put forward as far as possible by mutual repulsion disappears directly load apart to the outer edge of the sphere. Because against targeted electric fields cancel each other out is the size of the field in the center point 0 volts per meter and can continue flocking by the band landed cargo, with the result that the voltage on the bulb increases. 5 million volts is a good construction feasible.
That the voltage on the bulb still bounded, is because at a certain tension flow through ionization of the air leakage. (The Breakdown voltage of air is 3 million volts per meter) Also at further increase of the tension may take place via transhipment to earth near business drawn up. The size of the sphere, the distance to other objects, grounded , and the insulating properties of the gas in which the bulb is drawn up are the determining factors. If this be increased in equal measure the highest voltage will also be increased.
The vandegraaffgenerator has many services proven to be for example particle accelerator for Atomic Research and high voltage tests for materials research. Throughout the world there are still hundreds of active. The generator is also popular with public performances. One can, for example, the electric field in a fluorescent tube light up spontaneously. Put one a person under large load, then the hair will stand out in all directions. (The electrically charged hairs repel each other namely go).
This type of electrostatic generator is relatively simple to put together and is harmless as long as the diameter of the sphere under roughly 50 cm continues. It is recommended to keep awayelectronic equipment , because the high field strengths can semiconductorssuch as diodes and transistors, chips become defective.