MIT Physics Demo -- Inducing Dipoles with a Van de Graaff Generator

First, a dipole consisting of two conducting balls connected by an insulating rod swings at the end of a long plexiglass rod. The two balls are charged oppositely by touching it to a conducting rod in the field of a Van de Graaff generator. The generator is negatively charged, which induces a positive charge on the closer silver ball, and a negative charge on the further gray ball. Going around the generator, the dipole always aligns itself with the electric field, i.e. the silver ball always stays closest to the generator.

See the original video and more on MIT TechTV here - http://techtv.mit.edu/videos/1682-inducing-dipoles-with-a-van-de-graaff-gener...

Next, the Van de Graaff generator induces a positive charge on the closer side of a helium-filled conducting balloon, attracting it towards the generator. When it touches the generator, it picks up a net negative charge and is repelled away. When it hits the demonstrator (who can be thought of as "ground"), the net negative charge is removed and it is once again attracted to the generator.

The last clip combines these two ideas. The two outer bells are connected by a conducting rod and form a dipole in the field of the Van de Graaff generator, while the inner bell is grounded. The small balls are attracted to the outer bells the same way that the balloon was attracted to the generator. Once the balls hit the outer bells, they pick up a net charge and are repelled away. When the balls hit the grounded bell they lose their net charge and are attracted back to the outer bells. As you can see, the chimes do not work when the Van de Graaff generator is grounded.

A Van de Graaff generator is a machine that produces a lot of charge (in our case negative) on the outside of a conducting sphere. It was developed by (http://en.wikipedia.org/wiki/Van_de_Graaff_generator) Robert J. Van de Graaff, an MIT professor.

Category:

Education

Tags:

• mit mittechtv physics
• demo
• demonstration
• science
• engineering
• electricity
• electrostatics
• charge
• dipole
• induce
• induction
• electromagnetism
• introductor
• chimes
• bells
• electric
• balloon
• shock
• spark
• electrocution

[zed474]

@fortehlulz9999 I have a simple hand-crank one I used to teach my high school class that is rated for 150 kV. This model looks similar to one rated at 300 kV. The amperage is extremely low, however.

[AdOYOO]

creepy at the end with the chimes

[Reckab]

@fortehlulz9999 It's over nine thousant!!!

[fortehlulz9999]

What is voltage and amperage of this device?

[jimmyshitbags]

i have seen these used in dozens of demonstrations, but i can't think of a single real world use for a van de graaff generator other than for shocking kids with

[sniperboy102]

lol i remember shocking other kids after touching it

[randomerinc]

awsome were learning about it in school but it wont let me put it on a pen drive

[ChoiceDowsing]

Don smiths dipole generator looks like an ancient egyptian "tet". Maybe the egyptians were harnessing magnetic resonance energy. Just remarkable similarities. Very nice video. demonstrates effects well. thanks for posting.

[derifaa]

Amazing Video! I guess Electromagnetic induction would have been better if instead of keeping the dipoles tangentially, they would have been kept them normallly wrt field.