Transcript Template Title - University of Oklahoma Physics

Van de Graaff Generator
• A Van de Graaff generator is made by
a belt of a flexible insulating material,
running over two rollers (wheels), one
of which is surrounded by a hollow
metal ball.
1.
Power Supply that pulls off electrons.
2, 4. Rollers.
3.
Positively charged belt (lost some
electrons)
5.
Metal comb that drops electrons from
the ball onto the belt.
6.
Metal ball that gives up electrons to
the belt, then it is charged!
7.
Negatively charged belt (gained
some electrons from the ball).
8.
Grounding wand, it can give or take
electrons to make everything even
again.
9.
Discharge: A spark, a flow of
electrons through the air.
• The bigger the ball, and farther from
the ground it is lets you build more
charge up on it.
9
6
8
5
4
Schematic view
3 7
2
1
Proton Neutron
Electron
Van de Graaff Information
• The fundamental idea of friction
machine as high voltage supply
traces back to 17th Century.
• Generator invented to supply the
high energy needed for early
particle accelerators.
1931, Robert J. Van de
Graaff (left) poses with
his electrostatic
generator and Karl T.
Compton, MIT
president
• The first model was
demonstrated in October 1929,
using a silk ribbon bought at a
five and dime store as the
charge transport belt.
• Originally used as a research
tool in early atom-smashing and
high energy X-ray experiments.
The largest
VDG
generator,
on display
at the
Boston
Museum of
Science