Van de Graaff Demonstrations
Hair Standing Demos and You:
To perform the following demonstrations you will need a large milk crate that that can keep you insulated about a foot off of the ground.
Some people may not feel comfortable touching the VDG while it is running, so here is a trick to coax everybody into their first hair standing demo. Place an insulating plastic milk crate about 3 to 5 feet from your generator depending upon how big of of a VDG you have. Next, have the student take a paper clip and unfold it so that it is pointed and then have them stand up on the milk crate and point the paper clip at the VDG. If all goes well, their hair should start to stand up as they swoosh their hair back and forth.
Stand on an insulated platform while touching the VDG’s dome and allow your hair to stand on end. Most VDGs will do this demonstration.
If the student is using a paperclip to point at the VDG so they do not have to touch it, ask them to point the paper clip the other way and their hair will go down. If a spectator has a pointed paper clip they can point at the charged person and that will cause their hair to go down as well. Just don’t touch the charge person because they will take a nasty shock.
While standing on the platform with the VDG running, hold both hands in as a fist and keep them near you. Next, hold up one hand into the air and open your fist so your fingers are pointed away from you. You will feel the high voltage field immediately decrease as the electrons leave your fingers. Close your hand and the field will come back because the electrons are no longer escaping at a point.
Once your hair is in the air, take your right hand and move it around your head keeping it about 10 inches away. The electric field of your hand and that around you head will cancel out shutting off the field where ever your hand is. You will see your hair drop right at your hand because of the cancelation of the fields.
While pointing your fingers in the air as in the last demo, turn out the lights and you will see the electrons producing a blue glue as they leave your finger and ionize the air around you.
Take a fluorescent tube and have one student hold the tube that is standing on the ground. Have the person who is being charged on the insulated platform point at the tube and you will see the tube light up at the location it is pointed at. The charged person can also hold the tube and it will light up as well kind of like in Star Wars. Just make sure the lights are out so you can see.
Using the fluorescent tube, have the charged person grab one side and the person on the ground grab the other. Next have the person on the ground touch a sink and watch the light as a surge of electrons pass through them.
When standing on the crate, point with one finger at people that are close to you and they will begin to feel shocks in their feet and will shock anybody they touch.
When you point your finger at your local neighbor ask them if they can feel the breeze. This is the result of the electrons leaving your finger and then hitting the air molecules causing and exchange of momentum hence creating the breeze.
Take a piece of paper and rip it up into little pieces. Next hold them in your hand while standing on the insulating platform and open your hands. The paper will go flying out of your hands as it develops a negative charge that repels off of the negative charge on your hand. You can also do this with a balloon to make it levitate in one spot.
With more cut up paper, place it on a table. Insulate yourself on the generator and point towards the paper and you will see it link up and dance around your fingers. The kids really like this one!
Make sure the VDG is off before starting the demo. Have one person insulate themselves and then touch the generator. Next, have the students begin to link arms with the person touching the VDG. If the last person is shocked by an outsider, everybody will feel the surge of electrons pass through them especially the very last person because they feel the electrons from each person passing through them. This works best is everybody is insulated however do not do too many students if all are insulated because they will be too much charge.
That right. Just place ton pans on your head. For best results use the small 4 inch pans. The pie pans will fly off due to the electrostatic repulsion between them.
VDG and Props
Charging by induction can sometime be difficult to explain but the VDG make a great resource for doing and this is how: First place a charge on a balloon and hold it next to the VDG sphere. The free moving electrons on the metal will be pushed to one side. Touch the other side of the sphere and you will hear a shock as the electrons leave the sphere. Let go of the balloon and it will stick to the VDG. The balloon will also stick to the VDG just be bringing it near it because of the electrons being pushed to one side just not as well. This would also be a good way to introduce charge by polarization.
Light a candle and then blow it out. Bring the smoking wick near the VDG and watch how the electrostatic force interact. I wonder if the charge of the VDG will affect the direction the smoke goes?
Take a bunch of balloons tied to a string and tie them to the top of the generator. Watch what happens as the VDG is turned on. Cheers!
What is really neat is that you can also make an electrostatic motor out of the balloons by just pointing at them with your finger. Just get near it and point at the balloons and away they spin due to the transfer of charge to your finger.
Another cool thing is to point at the VDG with a straightened paper clip. By pointing the paper clip at the balloons, it will suck all of the charge from them and cause the balloons to attract to the VDG sphere. You can also point at the sphere and watch the balloons drop as the electric field quickly turns off.
The water molecule has molecular polarity due to the high electronegativity of the oxygen atom. Run water past the VDG and notice how it is affected. For those who are interested, research structure water. Washington State University a done a significant amount of work in this field and it is now starting to catch on.
Blow bubble at your VDG.
Place a light candle near the VDG and watch what happens!
It’s a simple electrostatic motor. Take a balloon and blow it up to only a small size and then attach a string to it. Next wrap the balloon in aluminum foil and stand two feet away from the VDG holding the string with the balloon dangling about 2 feet between you and the VDG. Allow your hand to touch the balloon and the balloon will begin to bounce back and forth between your hand and the sphere. This also works well using large bouncy balls.
Place the pie pans directly on the VDG and let them fly. The best pans are the small pans.
To turn the VDG electric field off, just point a sharp metal object at it. The electrons will immediately focus to the metal object and the sphere will not be able to develop a charge.
Bring a propane torch next to the VDG while running on it highest speed and allow the torch to arc to the top of the torch nozzle and it will night. Something about high voltage and a bottle of propane seem to add a lot of suspense to the crowd.
The sphere of the VDG is a capacitor because it can store electrons. The bigger the sphere, the more electrons it stores the larger the electric field. Actually, for every one inch in radius the electric field theoretically increase by 70,000 volts. Bigger is better! So try this if you can. If you have an extra sphere, place it on top of the generator while running and feel what happens to the field. You can use gazing globe if you have them.
Place a water bottle on top of the VDG and after about a minute of charging electricity will begin to arc through the water bottle. What is really interesting is that the bottle will store the charge and it will crackle in your hands after placing a charge on it.
Just as with magnets, bring a generator up to your old TV screen and watch how the electrons deflect the image on the TV screen due to electric field interfering with the passing of the electrons through the cathode ray tube.
Place your VDG next to a wall where phone lines are not running through and you will see it producing very loud bright arcs. I first found this out when running my VDG at the house while filming it and then it began to produce these arcs which almost sounded like firecrackers going off.
Turn the lights out so that the room is just about pitch black and then turn on the VDG. Next watch the sphere of the VDG and you will see same rippling point of electricity on the sphere and the discharge points move around it. Blow air on one of the discharge points and watch out!
To the right is simple illustration of an apparatus that cause Styrofoam balls to bounce back and forth between two charged plated. To make this you will need a clear tube using acrylic and metal foil for the top and bottom. The tube contains just a handful of Styrofoam balls. If one plate touches the VDG while the other side is grounded, the balls will begin to fly back and forth between the plates.
Take ¼ inch chicken wire or wire mesh form and wrap it in a tube like shape that has a diameter of about 8 inches. Next, place it on a running VDG and ask the student to touch the outside of the generator and then stick their hand on the inside of the wire cage. The electric field on the inside is zero so nothing will happen and its actually more of the cage of life. That’s why it’s safe to go into your car during a thunder storm and why you lose AM channels when driving through a bridge.
Using the VDG for Science Explanations
A great attribute of the VDG just like magnets is how you can feel the sudden increase in electric field as you get closer to the unit. Hold your hand 2 feet from a VDG and then hold it 1 foot away. Notice the huge change in the electric field! Just the same way, gravitational fields act like electrical fields in the sense that the gravitational field become much stronger as an object draws closer to a planet. Actually, the magic numbers is 4 times stronger. If you half the distance, the field strength goes up 4 times. If you double the distance away, the field strength goes down 4 times. Get the VDG out and feel the difference!