Massachusetts Institute of Technology
Sign in | Create Account

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.

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 Robert J. Van de Graaff, an MIT professor.

Comments (1)

interesting

Posted almost 6 years by Anonymous

You need to log in, in order to post comments. If you don’t have an account yet, sign up now!

MIT Department of Physics Technical Services Group

MIT Department of Physics Technical Services Group

Category: Science | Updated over 1 year ago

Created
January 16, 2009 16:40
Category
Tags
License
Creative Commons Attribution-NonCommercial (What is this?)
Additional Files


Viewed
44896 times

More from MIT Department of Physics Technical Services Group

MIT Physics Demo -- Inductor Radio

MIT Physics Demo -- Inductor Radio

Added over 6 years ago | 00:01:01 | 30724 views

Center of Mass Trajectory

Center of Mass Trajectory

Added over 5 years ago | 00:01:30 | 48235 views

Gyroscopes Made Easy

Gyroscopes Made Easy

Added over 2 years ago | 00:29:09 | 4891 views

The Wimshurst Machine

The Wimshurst Machine

Added over 4 years ago | 00:02:33 | 40531 views

Waves on a Chain

Waves on a Chain

Added over 5 years ago | 00:01:26 | 42321 views

MIT Physics Demo -- Pendulum and Magnet

MIT Physics Demo -- Pendulum and Ma...

Added over 6 years ago | 00:01:11 | 40407 views