How Does a Van de Graaff Generator Work?

[HorizonDelta]

kool

[samet9709]

Woow thats awsome

[blanknot]

Is a Van de Graaff Generator no more dangerous than rubbing your feet on the carpet and touching a door nob, or can it cause serious damage?

[JeffersonLab]

@blanknot It's certainly possible to build one that would be dangerous.

[AnubisEye009]

I wonder how this would work in low gravity or vacuum, or both.

[JeffersonLab]

@AnubisEye009 Low gravity won't change anything and it should work better in vacuum.

[U235hexafluoridedude]

@JeffersonLab It wouldn't work under vacuum due to the lack of a medium for coronal discharge. For optimum results one would place a VDG or better yet a Pelletron in anhydrous pressurized SF6.

[MegaTeenprincess]

the belt whch u hve used iz of whch material.?

wot else cn v use.?

[JeffersonLab]

@MegaTeenprincess I believe that the belt is latex. The materials you can use depends on what you choose for the rollers. Check the triboelectric series.

Imagine how difficult that would have been to understand if I hadn't actually used all the letters in the words...

[MegaTeenprincess]

i jxt wnt to knw wot is d rate of rpm of motor.?

[JeffersonLab]

@MegaTeenprincess It's rated for 60 rpm.

[MegaTeenprincess]

@JeffersonLab n wot iz d transparent tube called.?

[JeffersonLab]

@MegaTeenprincess The tube is just a tube. Don't think it has an official name. Stand-off tube, maybe? Isolation tube? It's job is to insulate the charged dome from the ground. It doesn't need to be transparent. Regular old PVC pipe would be just fine. I think ours is acrylic. As long as it insulates, it's fine.

[calif92627]

Looks to me like both of the brushes are on the curve of the belt. The first time I saw one work I thought that the brush needed to at the start of one curve and the end of the other. What this video totally leaves out is how does it know if it is pumping up or down. It was my idea that the electrons were pinched as the outside of the belt was compressed and released as the belt was bent so then both brushes needed to be at ends of the same flat side.

[JeffersonLab]

@calif92627 The video does not leave that out. We state that in order to tell whether electrons are being transferred to the belt or from the belt depends on the materials involved. Since we can't possibly anticipate every possible combination people might use in trying to make a VdG, we do the only sensible thing - we refer them to the Triboelectric Series.

[KanzlerM]

I think the concept of the Van De Graaff Generator would be better explained with a hand crank instead of a motor.

[JeffersonLab]

@KanzlerM What possible difference would that make?

[KanzlerM]

@JeffersonLab

If people see that it doesn't need to be plugged in or have batteries in order to function, it would make it clear that it works by converting motion into electricity (actually, uses motion to gather existing static electricity... but it's not like a simple transformer)

[leoclub626]

very well made video.

[thewii552]

is the speed controller a variac?

[JeffersonLab]

@thewii552 No, it's just a variable resistor.

[thewii552]

@JeffersonLab So would it get hot after the generator has been running for a while?

[JeffersonLab]

@thewii552 Basically, yes. It just sits there dissipating its (i^2)r worth of power.

[fellan12]

could you use Vinyl Laminated Polyester to the belt?

[JeffersonLab]

@fellan12 I assume so. It's not easy to make a judgement without seeing the actual piece you are thinking of using. There's nothing wrong with the choice of material, but it could be too thick, to brittle, etc...

[TheSupertecnology]

how much ampers does it generate?

[JeffersonLab]

@TheSupertecnology We've never measured or calculated it. But, safe to say that it's pretty low.

[TheV8freak]

so wil a latex belt work?



[JeffersonLab]

@TheV8freak It should.

[sajdrj]

What is the top pully made of?

[JeffersonLab]

@sajdrj My guess is nylon.

[mathscirocks]

one thing i am very curios about is since it's so simple why do they cost so much?

[JeffersonLab]

@mathscirocks "Charge what the market will bear."

[desenxuxator]

Yes, teflon belt instead of rubber one..is it OK?

[JeffersonLab]

@desenxuxator There's nothing wrong with using a teflon belt, as long as it doesn't become conductive under the voltages it will experience. The important thing is that it's the difference between materials that creates the static charge. If you have teflon on rubber, you'll get a separation of charge. It doesn't matter which one is the roller and which one is the belt.

[JeffersonLab]

@xXANGRYPURPLEHIPPOXx Not sure, exactly, but I'm betting it's latex.

[karlbiper14]

if I can use teflon tape as a band. ;)

[JeffersonLab]

@karlbiper14 Shouldn't be any reason why you couldn't, assuming that the teflon tape is strong enough to be made into a belt.

[karlbiper14]

I can use teflon tape to the band?

[JeffersonLab]

@karlbiper14 Sorry, but I don't understand what you mean by this. Are you asking whether you can use teflon tape as the band or if you can use teflon tape to fix or join the band?

[FutureInventions]

I built a Van de Graff kit. Oh man does it hurt.

[poptoping]

where did you get that one that you are using'

and how much does it cost

[JeffersonLab]

@poptoping We bought ours from Edmund Scientific, although there are many other companies that carry this and similar devices. Looks like they are currently selling the model we have for $500.

[keithecampbell1]

I just improved on my VDG by putting a teflon top ,alum.bottom roll. Found that I had a leak from the wire going to the dome and fixed that. NO HOLE IN DOME and I am getting a 20 inch spark this A,M.. Temp is 60 degrees, humidity is 50 %. I blew hot air down the tube for about one minute and started it up. The spark jumped about 20 inches and hit me on the chest. I have a bottle of sodium chloride sitting on top of the dome. Rubber belt is 3 inches wide, 30 inches long. Beats mythbusters sparks.

[JeffersonLab]

@keithecampbell1 I just have to ask... Why do you have a bottle of sodium chloride on the dome?

[keithecampbell1]

@JeffersonLab

The NaCl seems to act as a capacitor. It charges and discharges a really big spark all around the bottle. I just haappened to have the bottle sitting beside the VDG and wondered what it would do. To my surprise , it made bright sparks.. After stopping the motor and touching the bottle, it crackles and pops and flashes for several seconds . I am building a 1/3 scale VDG to see if cutting the hole hurts or helps. I believe it hurts the performance. Will let you know if you like

[JeffersonLab]

@keithecampbell1 Please, keep us informed.

[ActiveStorage]

@keithecampbell1 yeah. crystals are good capacitors

[keithecampbell1]

@JeffersonLab The bottle of sodium chloride will store a very good shock for up to 4 hours.! It is raining here today and I am getting 15 inch sparks. The temp is 60 degrees. If the mythbusters VDG got sparks in relation to it's size compared to mine, I wouldn't touch it. At 15 to 20 inches it feels like a spark plug on the lawn mower. Keithecampbell1

[keithecampbell1]

@JeffersonLab I just finished my 1/3 scale to my big VDG . 1" wide belt, teflon top,aluminum bottom roller, and a 3.5 inch dome. The dome is not spherical but flat bottomed stainless steel bowls (from my wife's kitchen) No hole in the domes yet. I will get spherical balls and cut a hole in one and not the other to see if cutting the hole helps or hurts performance. I think it hurts. Getting 7 " sparks on this one and 20 inch sparks on the 10" one. You MUST try NaCl on the dome.Stores for days.

[HybridWaterMan2]

@keithecampbell1 - mythbusters stuff sucks. If you got that knid of spark- you did well! Good job!

[spongebob107856]

We did this at school it is sooooooooooo fun

[keithecampbell1]

your suggestion of silicon adhesives worked well. I now have my VDG working and it is on you tube. Up to 10 inch sparks and NO HOLE in the globe. Believe me it does not have to have a hole. It may be even better with a hole but I don't know yet. I will change the top roller from PVC to teflon soon. I found a solid teflon pasta roller at Wallmart and intend to use it soon.. Should be even better. Thanks for the help.

[JeffersonLab]

@keithecampbell1 Awesome! Page address?

[keithecampbell1]

@JeffersonLab page is keithecampbell1 (don't leave out the e in keithecampbell1) thanks for the help,where were you guys when I was in school? Not even born I suspect.

[keithecampbell1]

do you know what type cement is best to join the ends of the latex rubber exercise belts for the VDG. I tried rubber cement (two kinds, tube and brush on) , super glue,(expensive type), contact cement, (spray on type) nothing holds well enough . belt is streching only 3 inches but keeps seperating at the joints. Can't keep it going long enough to make a video. thanks Keith

[JeffersonLab]

@keithecampbell1 I hear that silicon adhesives work well.

[keithecampbell1]

I am building a VDG with a 10 inch gazing ball. Is it necessary to cut a hole in the ball or can you connect the comb wire to the outside of the dome and just sit the dome on top of the PVC --anyone know? I have two Stirling Engines on YOU TUBE at Keithecampbell1 Thanks , kec

[JeffersonLab]

@keithecampbell1 It's best if the pick-off comb is inside the dome. If it's on the outside, it'll also bleed charge off the dome.

[keithecampbell1]

@JeffersonLab Hi again, I have finished my VDG with a rubber belt, nylon bottom roller , teflon top roller, 10" gazing ball WITH NO HOLE 46% humidity and getting 10" to 12" sparks. Ball is mounted on top of the PVC pipe, grounded to water pipe. Ran about two mins. when teflon came off and wrapped around the top roller shaft and broke my belt. Will fix today. Will post video on You Tube later. what would happen if the ball was filled with some gas like helium that can hold a charge? thanks KEC

[JeffersonLab]

@keithecampbell1 Congratulations!! I'm actually surprised that it works so well without having the pick-off comb inside the dome.

Filling the dome with some sort of gas or other substance shouldn't change a thing. The static charge is only on the outer surface of the dome. What's inside of the dome is irrelevant.

[keithecampbell1]

@JeffersonLab Thanks much for your help. This is a great site for people interested in science.How much difference does the length of belt or square inches of belt make?

[JeffersonLab]

@keithecampbell1 A longer belt helps in that you can get the dome further away from the ground. It'll allow the dome to charge to a higher voltage. You need to be careful that the belt doesn't get so long that it can pinch together in the middle. Opposite sides of the belt should attract each other and the further apart the pulleys are, the easier it is for the belt to come together in the middle. The wider the belt is, the faster you'll charge the dome (more current).

[rkshirey]

@keithecampbell1 cut the hole it ensures a maximum ark and higher performance

[rkshirey]

cool thanks ill use this in my science demonstrations keep it up

[hadabeesago]

hi i really like your quality work in putting that thing together, i am almost done building mine, since yours is doing a good job in producing good voltage i was just wondering, i read somewhere that said it is better to put the brushes on the side where the belt is rolling away or off from the roller, does this matter or do you know which side works better to put the brushes at and can i put brushes on both sides of one roller to make it more effective, or to eliminate guessing??

[JeffersonLab]

@hadabeesago FIrst of all, ours is a commercial unit. We didn't build it. In my mind, the only comb that really matters where it is is the bottom comb. It needs to be where the belt and the roller come together. If you place it where they come apart, the comb will tend to neutralize the charge on the belt.

[htirah100]

aww the resistor breaks down all the fun :(

[coldarc]

the comb on the top collect charges and transfer it to the comb on the bottom adding charges on one side of the belt roller side and collecting charge form the other belt roller side. its like a water wheel with water beeing lifted back to the top. there is a charge differential between each side of the rollers. one side have more charges than the other. the current is dc. the van de graff generator is a static capacitor and a charge separator at the same time. in a sense its a battery.

[jillifer24]

I work for the company that makes these :)

[JeffersonLab]

@jillifer24 That's shocking!

[SuperSkarmory2]

@JeffersonLab This Was an electrifying experienced video.

[Digadogup]

@JeffersonLab wow biggest pun

[jeobeahon]

@jillifer24 not to creep or any thing but... can i have one? pretty please?

[rkshirey]

@jillifer24 hook me up

[Gireesh092]

Can we use cellophane instead of rubber belt ??

[JeffersonLab]

@Gireesh092 From the standpoint of creating a static charge, yes, but I really don't see a cellophane belt being sturdy enough to last very long. Give it a try and let us know what happens!

[Gireesh092]

@JeffersonLab Ok Thanks 

[aaron45765]

@JeffersonLab Can I use a silicone rubber belt and a glass belt for the pully?

[JeffersonLab]

@aaron45765 Probably. You can run into trouble if the belt has a lot of carbon in it. It's conductive enough that you'll have a hard time delivering a lot of charge to the dome.

[Gireesh092]

Is the wire mesh touching the rubber belt ???

[JeffersonLab]

@Gireesh092 No, the mesh is not touching the belt. Having the belt scrape against the mesh only shortens the life of the belt.

[561inurface]

someone like me would have tons of fun just shocking myself over and over.... :D

[AHW214]

Is it OK that my belt is wider in some places ( I couldn't cut it right) and the belt seems to be closer to one side of the roller than the other. Also, my upper roller isn't very smooth.

[JeffersonLab]

@AHW214 It doesn't matter that the belt all the same width and centering it on the roller isn't important as long as the belt doesn't 'walk' off of it. THe rollers also don't need to be all that smooth, as long as they aren't so rough they damage the belt, it should be okay.

Did you ever get a good ground connection hooked-up?

[AHW214]

@JeffersonLab

I haven't got it grounded yet, but I've heard that there's a way to ground it through a variac speed control to the 3 prong plug. I'm going to use a variac on the motor. I got some sharpie on the belt while marking where to cut it (just a couple dots of sharpie). Would this cause problems? (make the belt conductive)

[JeffersonLab]

@AHW214 Nope, a couple of sharpie marks won't matter. You can run into trouble with rubber belts that contain relatively large amounts of carbon. They can become conductive at the voltages produced by VdGs. Those belts are usually blackish, though.

[JeffersonLab]

@EMW214 Gotcha. Good plan. Let me know how it turns out.

[AHW214]

Do you think steel mesh would work better than frayed copper wire?

[JeffersonLab]

@AHW214 Steel mesh is fine, too. The material doesn't matter so much. It's more important for the brush to be wide enough to span the entire width of the belt. It may be easier to do that with steel mesh than with stranded wire.

[AHW214]

@JeffersonLab

Do you think the way my brushes are positioned (theres a video on my channel showing them called Building a Van De Graaff Generator) is ok? I heard that the brushes should be positioned where the belt leaves the roller.

[JeffersonLab]

@AHW214 I don't know which way your belt runs, so I don't know how the brushes are positioned relative to the belt's movement. But, if you watch this video again, you'll see that our brushes are positioned where the belt and roller come together, not where they come apart.

[AHW214]

While testing my van de graaff generator with a drill at 1200 rpm as the motor, I only got 1/2 cm sparks but I'm suppose to be getting 8 inch sparks. I think there are 3 reasons why this is happening:

Humidity

Brushes were accidentally rubbing on the belt while I did this

I grounded it with my body

If anyone knows how to make bigger sparks please tell me.

There is a video about my van de graaff on my channel.

[JeffersonLab]

@AHW214 What are you sparking to? In your video, you just sort of point at the dome with your finger. Not sure if you were doing that to show about how large the sparks are or if that's how you make it spark.

Humidity is also a big spark killer. When it gets humid here, we go from 6-8" sparks down to 1-2" sparks.

[AHW214]

@JeffersonLab

I'n the video I'm trying to show how long the sparks are.

They are hard to spot, but if you look carefully you might see them.

Today where I live there is 57% humidity.

Do you think frayed copper wire is a suitable choice for both brushes?

[JeffersonLab]

@AHW214 57% RH isn't that humid, assuming the temperature isn't too high.

Stranded copper wire should work just fine for the brushes.

What are your rollers made from and what are you using for a belt? It's best if the brushes don't touch the belt, but that has more to do with keeping the belt from getting damaged than anything else.

Try connecting a wire to a metal drain pipe for a ground connection.

It also helps if the VdG's dome and the grounding dome are close to the same size.

[AHW214]

@JeffersonLab

My top roller is pvc wrapped in aluminum tape, and my bottom roller is pvc wrapped in plumbing teflon. My belt is made from excersice rubber. BTW I don't have a ground dome, I am trying to make these sparks by putting my arm near the VDG's dome.

[JeffersonLab]

@AHW214 If it's easy to do, try using bare PVC for one roller and cover the other with felt. The adhesive backed stuff you get with velcro works well. Also, you are grounding your lower brush, right? You wrote in yesterday about that. If the bottom brush isn't grounded, there isn't much hope in getting it working.

You can use a soda can attached to a dowel for a grounding dome. Make sure the grounding wire makes good metal to metal contact.

What on earth is exercise rubber??

[AHW214]

@JeffersonLab

Let me rephrase exercise rubber. I should have said exercise band or resistance band. Search resistance band in google. It's basically a big band made of latex.

Do think it would be ok not to change the rollers since teflon is negative and aluminum is positive? Also while I was doing a test run, the top brush was accidentally rubbing against the belt and it made white streaks on the belt. Should I make a new belt or is this fine?

[JeffersonLab]

@AHW214 The belt should be fine. It's just that if you leave the brush rubbing against it, it would eventually cut through the belt. And, the brush doesn't need to touch the belt for the charge to transfer, so nothing much is gained by having them touch.

[JeffersonLab]

@AHW214 Yeah, but aluminum tape and plumbing teflon aren't known for their durability. And, without being able to see them, it's hard for me to judge whether or not they 'look like' they'll work. Plus, bare PVC is pretty good on its own and it's fairly easy to cover another roller with sticky-back felt.

Get a good ground hook-up first and see if that fixes things.

[AHW214]

@JeffersonLab

If you want to see what the rollers look like there is a video on my channel that will show you. The video is called Building a Van De Graaff Generator. If the look OK to you could you tell me?

[JeffersonLab]

@AHW214 As far as I can tell, the rollers look fine. There's nothing about them that screams 'yikes' to me.

[AHW214]

@JeffersonLab

Should the grounding dome be connected to the bottom brush of the VDG or to ground?

[JeffersonLab]

@AHW214 Ideally, it's the same thing. Running a wire from one to the other and then to the ground is the same as running each one to the ground individually. In ours, the whole case is grounded, so anything that electrically connects to the case is also grounded.

[AHW214]

@JeffersonLab

BTW during my test with the VDG, I grounded it to my body. If I were to ground it to a 3 prong power cord would I get better results?

[JeffersonLab]

@AHW214 If you power it with a 3 prong power cord, use the ground wire that it provides. Otherwise, I would run a wire from the plumbing system or the HAVC air ducts.

[EMW214]

@JeffersonLab

How do you attach the ground part of the 3 prong plug to the motor safely?

[JeffersonLab]

@EMW214 Don't you have your motor on the outside of your VdG? It isn't actually mounted to its base, right? If that's right, grounding the motor's case isn't going to do anything for you. Also, I wouldn't try to modify a cord just to get a ground line. One mistake there could be very, very bad. Running a wire to a metal drain pipe will work just as well. It'll just look a bit messier.

[AHW214]

I am making a van de graaff generator, how should I ground my bottom brush?

[JeffersonLab]

@AHW214 The easiest way is to use the ground line from a three prong power cord. Ground the case with that and attach the bottom brush to the case.

[moneyjr1122]

is this doesn't prove atoms then i don't know what

[mdragondude123]

another question what materials are your brushes made of and what are the best materials you can make your rollers out of?

[JeffersonLab]

@mdragondude123 The brushes are just a wire mesh - probably steel, but I don't know for certain. As for roller material, you need to consult the Triboelectric Series. You're best off if you choose two different materials that are far apart from each other with the belt material in between. Our machine's lower roller is covered in felt and the upper roller is, I believe, nylon.

[mdragondude123]

if you take a cordless drill and use that as your motor do you need a ground and if so how do i make a ground out of it

[JeffersonLab]

@mdragondude123 You really do need a ground. For the VdG to charge, it needs to transfer change from somewhere. The best source for this is the ground. Let's say that your VdG is completely isolated. The bottom comb can only draw charges from the base. As the base becomes charged, it gets harder to remove additional charges. Attaching the base to the ground solves this problem. It's like taking a bucket of water from the ocean. As far as the ocean is concerned, nothing happened. (Continued...)

[JeffersonLab]

@mdragondude123 (...continued) You're going to want to run a wire from the VdG's base to something in your house that's grounded. Try running a wire to the drain pipe under the sink. Attaching the grounding wire to the heating/AC conduits should also work.

Good luck!

[dbradley771]

What is the name of the model?

[JeffersonLab]

@dbradley771 I'll assume you mean the Van de Graaff and not Joanna...

It's a Winsco model N100-V manufactured by Wabash Instrument Corporation.

[dbradley771]

@JeffersonLab Thanks!

[TheRealVerbz]

You guys are so cool.

:oD

Right on for answering my weird questions.

[TheRealVerbz]

When we work out, our muscles get hot. Why doesn't that heat convert into static electricity?

Is it possible to convert that into static electricity?

And do our spinal cords and head resemble a VdG?

[JeffersonLab]

@TheRealVerbz A static charge is created when two dissimilar objects come into contact with each other and are then pulled apart. Some substances have a greater affinity for electrons than others, so there's a transfer from the one to the other. You can see a relative ranking of materials by looking at a thing called the triboelectric series.

Our heads and spinal cord resemble a VdG only in that they both look like round things on a stick. Other than that, there's no real resemblance.

[TheRealVerbz]

If a coil of copper wire is -1 on the diamagnetic scale and water is -.91, then rather than using a 16 gauge copper wire to coil around an electro-magnet, couldn't you use a 16 gauge stream of water in a tube injected with nano-particles of Bismuth?

Bismuth is -16.6. Plug the ends of the tube with stoppers and make sure some copper is sticking through the stopper to touch the water. Now you have leads to your power source and an electromagnet 16 times more powerful with the same energy?

[JeffersonLab]

@TheRealVerbz Well, diamagnetism is something completely different. What you're really after is conductance. As far as (room temperature) elements are concerned, it's hard to beat copper. Silver's better, but kind of pricey. In fact, when they were making the electromagnets for the uranium separators during WWII, they made the wire from silver borrowed from the treasury due to needing copper for other things.

[TheRealVerbz]

When you touch someone after touching the generator, it shocks people.

That leads me to believe that it charges your body.

What would happen if you touched the generator for long periods while sitting on a wooden platform making sure nothing touches you?

Or would you want your feet touching the ground?

[JeffersonLab]

@TheRealVerbz If you are insulated from the ground, charge would gather on you, making your hair stand up. For something like this, a 'long time' is 15 or 20 seconds or so. Once you're on there for that long, you've reached equilibrium with the generator - the amount of charge leaking off of you into the air is balanced by the generator providing you with additional charge. Staying on there for more time doesn't result in more charge.

[TheRealVerbz]

@JeffersonLab hmmm very cool.

I've been doing quite a bit of research on ancient hieroglyphics and some of them seem to resemble van de graff generators.

I keep seeing a person holding 2 rods while sitting on a stool as not to be grounded.

I've been studying Bio-Voltage also from electric eels, fire-flies and human 'Chi'. I think the hieroglyphics are related to charging one's self somehow.

So I'm trying to figure out what holding 2 rods does if you were surrounded by a lot static electricity.

[JeffersonLab]

@TheRealVerbz If you are holding a pointed rod near a charged object, the charge would tend to be drawn to you from the object through the rod. If you were charged and were holding a pointed rod, the charge would tend to leak off of you through the rod.

Round objects tend to hold charge (that's why VdG's have round domes) and pointed object tend to bleed charge.

[TheRealVerbz]

@JeffersonLab So you are only charged with as much static as the generator itself?

So in hypothetical theory... if perpetual energy were possible and you created a big enough charge, could a person retain that charge? And if there is squared the amount of static than makes up the mass of an object, would that object levitate?

Why does tinsel and confetti hover or get repelled? Is it because the static squares the energy that makes up the mass of the tinsel?

[JeffersonLab]

@TheRealVerbz The amount of charge a person ultimately picks up from the VdG depends on the operating voltage of the VdG and the shape of the person. The person essentially gets turned into a capacitor.

An object is going to float if the force of repulsion is equal in strength by oppositely directed to the force of gravity. The EM force is much stronger than the gravitational force, so it isn't too hard to get enough charge on a light object to make it float. Think of static cling... (cont)

[JeffersonLab]

@TheRealVerbz (cont)... The slight imbalance in charge between a sock that's stuck to a towel creates enough force to overmatch gravity. If it didn't, the sock would fall. The whole planet is trying to pull the sock off the towel. It is defeated by the static charge on the sock and towel.

[carlosjunior57]

what materials can I use the top rope and pulley bottom? Can I use brush with copper?

[JeffersonLab]

@carlosjunior57 Whatever you use, it's helpful if they are on opposite sides of the triboelectric series with your belt material more or less between them. There's nothing wrong with using copper as one of the two pulleys. Just consult the triboelectric series to see what other material would be a good match. Our pulleys are felt and, I believe, nylon.

[ventje5haar]

Maybe tire inner tubes don't work because they use carbon as a filler for the rubber.

( but i'm not sure on that...)

[JeffersonLab]

That could very well be the problem. Carbon containing rubber isn't a great material to use for the belt. While it insulates at low voltages, higher voltages result in arcing. The end result is that the charges 'bleed off' before they make it to the upper dome.

[bonarka]

I was trying to made one van de graaff generator in my home but it does not work. The upper roller is made of rubber and lower is made of metal (it's drives by the engine from the drill). As a rubber belt i"ve got the innertube from bike. the lower comb is attached to the gdound and the upper comb to hollow sphere. Help me please!!!

[JeffersonLab]

Does it do anything at all when it runs? Does it collect any change at all? If you could post a video of it, that may help.

[bonarka]

What is the lower and upper pulleys made of? I've made the van de Graaff generator (at home) but it doesn't work. In my generator the lower pulley is made of metal and upper is made of rubber. I need your help. I will send you more informations and photos if you want.

[JeffersonLab]

Our lower pulley is covered with felt and our upper pulley is nylon, I believe.

[mackenzie235]

use a home sewing machine motor, it comes with a speed control.

[EricaDizzle]

This video is amazing. I learned about how this device works in class, but I didn't get it at all... after watching this it seems so obvious.

You've helped me greatly!

[SanchezAfricano]

is the grounding wire connected to the same cable that provides power to the motor? Isn't it dangerous to feed high voltage electricity back into a wall socket?

[JeffersonLab]

Yes, the grounding wire is using the ground provided by the three wire power cord. While the voltage we're feeding back into the wall is high, the current is low, so there isn't any danger to people or to the building.

It does cause problems for the computers in the back of the room, though. If they are on when we discharge, the machines will often reboot. Having something that is electrically sensitive hooked-up to the same ground as the Van de Graaff isn't a great idea.

[shinrage13]

speak spanish?

[JeffersonLab]

Not well enough to be understood. You can try turning the closed captions on and use the translation feature to convert it into Spanish.

[RomanianUser]

google translate

[mistershadeslayer]

where did u get the motor from ?

i am trying to find one .... any ideas?

[JeffersonLab]

We bought our Van de Graaff, so the motor came with it. Here are the specifications, for what it's worth:

Dayton AC-DC series motor

Model Number 2M033A

115 Volts

1/15 Horsepower

1.2 Amps

60 RPM

[lingrivedfed]

What is the grounding wire actually for. This was not made clear. Where is it connected? Thanks!

[JeffersonLab]

The grounding wire connects the base of the Van De Graaff to the ground. Connecting the base to the ground provides the device with an inexhaustible supply of electrons. Let's say that the case weren't connected to the ground and that it was on a well insulated table, so it's basically an isolated system. Electrons from the base would be brought up to the dome by the belt. The dome would become negative but the base would become positive. As the base becomes more and more positive...

[JeffersonLab]

...it gets more and more difficult to remove electrons (since opposite charges attract). Connecting the base to the ground allows electrons from the earth to neutralize the base. The earth becomes positively charged, but, since the earth is so much larger than the base, it doesn't really become a problem. It's kind of like taking a cup of water from the ocean. The level of the ocean goes down, but no one is going to notice.

[JeffersonLab]

There is also a port on the base that we can plug other devices into. This becomes important in some of our other videos. We attach a 'grounding dome' to this port, mainly so we can discharge the main dome. It completes the circuit. Electrons go from the earth, up the belt, onto the dome and back to the earth somehow. The grounding dome is a convenient way to get them there. You can see this in action in the oddly named 'Big Sparks, Little Sparks!' video.

[BlueGolem]

Im building one about that size right now : )

My rollers will be made from 2 diameter nylon rod.

The top roller will be covered with silicon tape to put it on the opposite side of the triboelectric series from the bottom roller.

The case of an old UPS will be the base and house a 3 speed fan motor. The top-load will be comprised of two stainless mixing bowls.

Perhaps I will make a brief film of its construction.

Thank you for this demonstration! It helped to confirm a few things for me.

[JeffersonLab]

What are you using for the belt?

[BlueGolem]

3 inch wide rubber exercise band.

[theducktapeking]

I tried to make one with a soda can and such... Never got it to work :(

[JeffersonLab]

I have seen one like that, so it can be done. If we can get one working, we'll make a video showing how to do it.