How Can I Demonstrate Electric Forces Using a Van de Graaff Generator?

[RossMiller]

I need to perform a demonstration of electric forces. Something more substantial than weak static charge forces would be best. Could someone please help me by describing a practical way for me to put a charge onto something lightweight and then generate an electric field to move it back and forth. A way to make an electric field that has a variable and easily controlled magnitude and direction is what I am looking for. Thanks.

 

[berkeman]

I need to perform a demonstration of electric forces. Something more substantial than weak static charge forces would be best. Could someone please help me by describing a practical way for me to put a charge onto something lightweight and then generate an electric field to move it back and forth. A way to make an electric field that has a variable and easily controlled magnitude and direction is what I am looking for. Thanks.

Welcome to the PF.

One demo would be to show a naked CRT and explain how the electrons are boiled off of the cathode at the base of the neck, and accelerated through the electron gun lenses in the neck and out to the anode/face of the CRT. It's the electric field of the lens elements and the high + voltage of the anode surface that accelerates the electron beam enough to light up the phosphors coating the inside of the face at the anode. Pretty impressive acceleration!

One downside of this demo is that a naked CRT can expose some pretty high voltages, depending on how you package the demo. If you guard all the HV generating circuitry, the anode button and the neck endcap are pretty well insulated.

EDIT -- The x-y deflection of the electron beam to paint the picture on the CRT face is done with magnetic fields generated by currents in the deflection yoke, but the acceleration of the beam toward the face/anode of the CRT is all due to the electric fields generated by the high voltages in the electron gun and on the anode.

 

[jim hardy]

For a demo you want something visual that moves.
could any of these be refined?



http://www.scientificamerican.com/article/bring-science-home-static-electricity-attraction/

 

[DrZoidberg]

Here are a few more videos that might inspire you.