Van de Graaff Generator 5A50.30
The Van de Graaff generators are located in the Electrostatics Cabinet, B3. The plastic stool is located on the top of the Electrostatics Cabinet, A1 or A2.
There are many demonstrations that use the Van de Graaff; the one described below is very popular with students of all ages.
Note 0: The shock from the Department's Van de Graaff is not likely to be painful or cause injury, but it will get your attention, and some people may dislike it.
Note 00: The Department's Van de Graaff charges positive, due to the materials used for the belt and rollers.
Put the Van de Graaff on a table so that the big silver ball is at least one meter from other objects (to minimize leakage current).
To see if the Van de Graaff is going to work well:
- Turn the power on and see if a spark starts to jump between the big silver ball (high potential) and the small silver ball (ground).
- If a spark does jump, grab the rod supporting the ground ball and touch the ground ball to the big silver ball.
- Turn off the machine.
The Van de Graaff might not work well if the air is humid, or if the belts are old.
If the Van de Graaff is working well, then:
- move the Van de Graaff to the front of the table, closest to the audience
- remove the ground ball, and attach the grounding stick (shown in picture) to the ground terminal
- place the plastic stool in front of the Van de Graaff about 60 cm away from the table
- ask an audience member (preferably one with long, fine hair) to stand on the stool and place one hand on the big silver ball
- place the tip of the grounding stick on the big silver ball
- turn on the machine
- remove the grounding stick from the big silver ball. The audience member's hair should stand up!
- angle of repose of audience member's hair should be a function of distance from tip of grounding stick to big silver ball.
- when done, place grounding stick on big silver ball, and turn off machine.
Note 1: multiple audience members can be taken for a "ride" on the Van de Graaff without switching the machine on and off, through proper use of the grounding stick: people are only allowed to put their hand on the big silver ball or take it off if the big silver ball is grounded.
Note 2: while at high potential, the audience member may get a shock if he or she gets too close to the table, too close to you, or too close to other audience members.
