Friday, December 19, 2014

Van de Graaff Generator

A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate very high amounts of electrical potential on a hollow metal globe on the top of the stand. It was invented by American physicist Robert J. Van de Graaff in 1929. The potential difference achieved in modern Van de Graaff generators can reach 5 megavolts. A tabletop version can produce on the order of 100,000 volts and can store enough energy to produce a visible spark.

A Van de Graaff generator operates by transferring electric charge from a moving belt to a terminal. The high voltages generated by the Van de Graaff generator can be used for accelerating subatomic particles to high speeds, making the generator a useful tool for fundamental physics research.



The Van de Graaff generator was developed, starting in 1929, by physicist Robert J. Van de Graaff at Princeton University on a fellowship, with help from colleague Nicholas Burke. The first model was demonstrated in October 1929.  He got $100 from his department and built better generator. By 1931 he could report achieving 1.5 million volts, saying "The machine is simple, inexpensive, and portable. An ordinary lamp socket furnishes the only power needed." According to  patent application, it had two 60-cm-diameter charge-accumulation spheres mounted on borosilicate glass columns 180 cm high; the apparatus cost only $90 in 1931.

Van de Graaff applied for a second patent in December 1931 and got it. It was assigned to MIT in exchange for a share of net income.

In 1933, Van de Graaff built a 40-foot (12-m) model at MIT's Round Hill facility, the use of which was donated by Colonel Edward H. R. Green.

http://science.howstuffworks.com/transport/engines-equipment/vdg.htm



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