PLEASE NOTE
If you've come here by way of my
High-voltage projects sub-menu
, you will have seen my warnings on electrical safety. If you haven't read
this yet, please click on that link and do so before proceeding.
At the time of writing (May 2005), the title of this page is something of a
misnomer, if the truth be told. I've currently only got one Van de
Graaff machine, made way back in 1967; and that one wasn't a great success.
(The sole menu item at the bottom of this page leads to a description of
this project; I hope to add more in the not-too-distant future.)
To my way of thinking, Van de Graaff machines are somewhat comic-looking
things, in a vaguely alarming kind of way. You may have seen one in school.
The standard experiment is to get some student to stand on an insulating
platform (the term "plinth" from 1980's computer adventure games springs to
mind
Another experiment you can do is to put some breakfast cereal on top of the
dome before switching on, as shown in the Quicktime movie on
this page.
(School cleaners must hate teachers who do silly things like this!)
Dr. Robert J. Van de Graaff (1901-1967)
was the inventor of the high-voltage generator which has come to be named
after him. From articles I have read and pictures I have seen of the good
doctor (like the one on
this page
), I gather that he had a playful approach and was a popular lecturer.
For all the fun and games, though, Van de Graaff machines have had an
important rôle in physics. The very high voltages which can be generated are
valuable for research into nuclear reactions and related matters. Although
small machines are usually considered fairly harmless, the big ones can pack
a wallop. (Follow the links on that last page mentioned above for an
excellent history of these devices, and to see some pictures of the big one
built at MIT by Dr. Van de Graaff himself.)
This page
is part of a website run by an authority on electrostatic machines of all
kinds. He has built twin VDG units rather like Dr. Van de Graaff's own
original machine (see the previous link above), although somewhat smaller.
There are some interesting links to historical belt-driven predecessors of
the modern VDG.
Here are some links to various sites, some giving further historical
background, some dealing with how these machines work, and some detailing
models built by experimenters:
http://bama.ua.edu/~jharrell/PH106-S06/vandegraaff.htm
http://chem.ch.huji.ac.il/~eugeniik/history/graaff.html
http://wvlightning.com/graaff.html
http://www.resonanceresearch.com/Robert-J-Van-de-Graaff-high-voltage-electrostatic-generators.htm
http://www.engr.uky.edu/~gedney/courses/ee468/expmnt/vdg.html
http://www.thebakken.org/artifacts/VandeGraff.htm
http://members.aol.com/lyonelb/vdg.html
http://web.singnet.com.sg/~sengam/construction.htm
http://www.everything2.com/index.pl?node_id=156164
http://www.scitoys.com/board/messages/7/600.html?1113571253
http://www.esdsystems.com/whitepapers/wp_triboseries.asp
(The last link above deals with the "triboelectric series", which describes
how physical contact between different substances can cause positive or
negative charges to be acquired by those substances. This is important with
reference to materials used for the belt and the rollers in a Van de Graaff
machine; however, it also has applications in other, more general,
contexts.)
Don't think that this list is exhaustive! There's lots of stuff on the
internet about high-voltage projects in general, and Van de Graaff machines
in particular. Use a good search engine, and have a dig around yourself to
find plenty more!
VAN DE GRAAFF MACHINES
My first attempt at a Van de Graaff machine
My home page
Preliminaries (Copyright, Safety)
Van de Graaff machines
), and put one hand on the dome of the device
while the teacher switches the motor on. The high-voltage charge which
builds up makes the subject's hair stand on end, much to the amusement of
the class.
Bill Beaty's Van de Graaff page
shows him doing this; he has longish hair and the effect is quite
spectacular. (Have a look around
Bill's site;
he's an interesting character
and his pages are very informative, as well as being quite amusing.)
This site
has a Quicktime movie featuring a girl with long hair undergoing a
startling transformation caused by one of these machines, to considerable
hilarity from onlookers.
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