Transcript Van de Graaff Generator

Van de Graaff Generator
Goals
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Learn how a Van de Graaff generator
works and what it is used for
Explain demonstration/experiments that
involve the Van de Graaff generator
What is it?
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The Van de Graaff generator is a device
that separates electric charges
mechanically.
This produces a high voltage with a low
current.
Safety
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Do not allow students to use the Van de Graaff generator
unsupervised.
People with cardiac pacemakers should never operate the
generator or come in contact with it.
Obviously, we are dealing with high voltage here. Stay about
three feet away from the collector while it is charged.
Always discharge the collector dome between experiments and
when you are finished.
The motor produces a lot of heat that could damage the belt or
the motor itself. Do not run the generator continuously for long
periods of time.
Leave the upper and lower combs alone.
Keep the entire device clean and dry.
Handle the aluminum parts with care.
How much voltage?
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Voltage is…is commonly used as a short
name for electrical potential
difference
Which means is a measurement of the
energy contained within an electric field,
or an electric circuit, at a given point
This VdG generator can produce anywhere
from 10-200 thousand volts (V).
It is safe because the current is quite low.
What does it look like inside?
Metal Sphere
Insulating tube
Conveyor belt (rubber)
Metal Combs
Base (Electric motor)
How does it work?
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The VdG generator is a charge separator.
When turned on, the belt begins to move,
picking up negative charges deposited by the
metal comb at the base.
The belt then transfers the charges to the metal
comb at the top of the generator.
The metal comb is attached to the metal sphere
and thus transfers the negative charges to the
sphere.
How is the VdG like the cashier’s
check out at the grocery store?
Think of the groceries
as charges.
Metal Sphere
Insulating tube
Base (Electric motor)
What is it used for?
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Used during early research into radioactivity and
atomic structure, used as power source for
particle accelerators.
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Still used to power high energy x-ray machines
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Useful in laboratory study of electrostatics
VdG Experiments
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Sparks!
Shock Line
Crazy Hair
Flying Cereal
Light off, light on.
Flying Fur
Anyone for Pie?
Questions
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Explain in your own words how the VdG generator
works.
Explain in words and using a diagram how:
a. Someone’s hair can stand up
b. How a shock can occur
c.
How something can be repelled by the VdG