Talk:Van de Graaff generator

message: Maybe there are two different versions, but the version I made used the triboelectric effect with a rubber belt and rollers made of different materials.  The power supplied was only used to drive the motor.  Am I right in thinking there are two different kinds?  If so, both should be addressed. - Omegatron 14:21, Mar 30, 2004 (UTC)
I agree with both.  I did not look at the charging and un-charging mechanisms on the MP tandem I used, but I believe its operation was closer to the description in the article.  It did have a high voltage supply to charge the belt.  On the other hand, small demonstration Van_de_Graaff_generators I have seen use unlike materials, as above.  I don't know whether nuclear reactions have been induced with this type of charging.
--David R. Ingham 18:31, 7 August 2005 (UTC)
thread_title:  Belt charging 

message: Re:  http://en.wikipedia.org/w/index.php?title=Van_de_Graaff_generator&curid=52642&diff=20358302&oldid=20305308
I agree with this edit, but would like to hear other opinions.  The exhibit at the Smithsonian is or at least was called "Atom Smashers".
I think that is archaic, but I am not sure.
I agree with this edit too. I am pretty positive that is archaic.  —Preceding unsigned comment added by 24.187.35.214 (talk) 23:44, 27 January 2009 (UTC)
thread_title:  Popular name for nuclear reaction experiments. 

message: The whole thing about connecting the wire to the inside of the sphere is false. i made a vdg machine and connected it to the outside of the sphere, and it worked just fine. anyway outside and inside are relative terms, thus the whole concept of ice pail effect does not make sense to me.Also going by that logic a circular plate would not carry any charge as it would not know which side to put the charge on(it can be assumed to a sphere of infinite radius)  Pranay
:The wire can be connected to the outside of the sphere; the crucial point is to have the charge removed from the belt inside the sphere, where there is little electric field. Theoretically, a closed conducting shell has no electric field inside, no matter how much charge is on the outside.  Although the sphere has an opening, only a small amount of electric field will get in.  The principle is that like charges try to get as far away from each other as possible, so they concentrate on the outside of conductors.  Charge liberated from the belt will migrate to the outside of the sphere, if given a wire attached to it anywhere. --ChetvornoTALK 15:24, 29 December 2007 (UTC)
replies: text: A circular conducting plate does have the same amount of charge on both sides, but the charge is concentrated on the rim, as far away from the other charges as possible.  --ChetvornoTALK 15:24, 29 December 2007 (UTC)
thread_title:  Sphere Connection 

message: I've just uploaded the picture, but  I think, it is not perfect: see the talk page at the Wikimedia Commons. -- Harp 15:24, 30 June 2006 (UTC)
thread_title: Schematic view

message: Can anyone tell me why small commercially available (for about $450) Van de Graaff generators with 14 " diameter globes are said to produce potential differences of about 400,000 to 450,000 volts, and yet Van de Graaff's huge original machine (15 ft globes), at the Boston museum of Science, only generates a potential difference of about 2 million volts?  My supposed 450,000 volt device is only capable of producing a 12 " discharge on a really good , very dry day, yet I've seen machines in some science museums throw discharges that looked like bolts of lightning clear across the room.  I had always assumed the voltage of such sparks to be a couple of orders of magnitude greater than that of my little machine.
:Umm, marketing? ;-)
:More seriously, the first few tens of kilovolts are easy, and after that, each additional volt becomes more expensive. There's also the question of current. That machine at the MoS can produce substantial current as well as 2MV; it recharges fast enough to throw a multi-megavolt spark every second or two, so there are quite a few electrons being pushed around (and a lot of primary power being consumed).
:The usual value assumed, BTW, for the breakdown voltage of air is about 3KV/mm, but corona discharges obviously have a huge impact on reducing that value or the MoS machine would never produce the sparks that it does.
:Interesting link (PDF):
::http://library.abb.com/GLOBAL/SCOT/scot221.nsf/VerityDisplay/B0900B81040BA3F6C12570750029D71F/$File/ISH05_Humidity.pdf#search=%22breakdown-voltage-of-air%22
:Less technical link:
::http://www.sciencebuddies.org/mentoring/project_ideas/Elec_p032.shtml?from=Home
:Atlant 16:10, 30 August 2006 (UTC)
thread_title:  More bang for the buck? 

message: The starting description talks about E1 and E2 electrodes. It would be easier to understand if the 
schematic view showed those electrodes as well.
::and/or if the callout numbers in the schematic view were explained in the description.
  Mcswell 01:40, 24 October 2006 (UTC)
thread_title:  Schematic view 

message: Heed the warning. A pint-size Leyden Jar can be lethal. A while back, my wife asked me to build her a simple Leyden Jar that she could show to her 2nd grade class. She already has my small Science First Van de Graaff Generator, so I warned her not to let the Leyden Jar near the operating Van de Graaff Generator. She did as she was told. However, I recently was demonstrating my large Van de Graaff Generator to a group of Boy Scouts in an Electricity Merit Badge class and had left the Leyden Jar on the floor near the Van de Graaff Generator. After the demonstration, I casually picked up the Leyden Jar and pointed my finger at the metallic-painted ping pong ball at the top of the jar.... I remember a flash of extreme pain, after which one of the other instructors said he hoped I don't normally use such language in front of boy scouts. --Etymolog 04:47, 15 December 2006 (UTC)
replies: text: Thanks for the warning! Van de Graaffs are usually thought of as harmless because of the small current, but capacitors can accumulate enough for a lethal shock. Caveat emptor. --ChetvornoTALK 16:30, 29 December 2007 (UTC)
thread_title:  Leyden with Danger 

message: The title and first line don't agree. Deizio talk 08:51, 21 January 2007 (UTC)
thread_title:  Graaf or Graaff? 

message: I know of a page that shows you how to construct a Van de Graaf generator with pieces you would usually call trash. The site is here: . Please tell me if it would be a good addition to the external links section. Slartibartfast1992 16:32, 10 February 2007 (UTC)
replies: text: I think it would, but not that page, but this. -- Harp 13:13, 21 March 2007 (UTC)

text: Oh, yeah. That'd be better. I'll just go ahead and add it.Slartibartfast1992 00:46, 26 March 2007 (UTC)
thread_title:  Another external link 

message: This is a wonderful article, but I had a question about one small point of the explanation of operation.  In addition to the transport of positive charges to the sphere, the example shows a transport of negative charges in the other direction, sprayed on the belt by E2, the sharp electrode in the sphere: "the high potential difference ionizes the air inside the sphere, and negative charges are repelled from E2 onto the belt".  Isn't the inside of the sphere at nearly constant potential?  The only electric field inside the sphere should be from the tiny amount of positive charge on the portion of belt inside the sphere.  So what creates the negative ions?  The Van de Graaff explanations I've seen that show transport in both directions, it is caused by the triboelectric effect of the upper pulley. --ChetvornoTALK 16:19, 29 December 2007 (UTC)
thread_title: A small error?

message: Sorry for removing the part about applications, I just had never heard of these applications and thought they were misconcieved extrapolations of it being a high voltage source and that other high voltage sources (which I've seen on accelerators where I study) are used for the purposes here stated.
Sorry also about not just placing a  tag as it is proper conduct here in WP. I got distracted and when I got back to this and found good sources found out someone had already done the revert I was about to do.
I'll add a source to this application so that other people don't make my own mistake JunCTionS 22:58, 30 July 2008 (UTC)
replies: text: One of the great things about Wikipedia is running into something you've never heard of; after having this occur scores of times, I'm now very cautious about deleting something I see only on the Wikipedia, even if its in a field I think I know pretty well. References are good. Mind you, there are crackpots about, too....which makes it more interesting. --Wtshymanski (talk) 13:16, 31 July 2008 (UTC)
thread_title: Applications

message: all your hair get negatively charged so negative charges attract eureka! you hair stands upFdkmx236 (talk) 19:36, 23 April 2010 (UTC)
thread_title:  answering the question 

message: As noted by AlexWillisson above, the illustration does not match the description in the text. The text describes a generator where the charge is provided by a high voltage source, the image is one charged by friction due to the different material of the rollers. Also, the legend with the picture is:
:3) upper roller (metal)
:..
:6) lower roller (for example an acrylic glass)
But when you look at the picture file page [File:Van_de_graaf_generator.svg|File:Van de graaf generator.svg] (don't know how to link to such a page, just click the picture.) there it reads:
 
# hollow metallic sphere (with positive charges)
#     electrode connected to the sphere, a brush ensures contact between the electrode and the belt
#     upper roller (for example in plexiglass)
#     side of the belt with positive charges
#     opposite side of the belt with negative charges
#     lower roller (metal)
#     lower electrode (ground)
#     spherical device with negative charges, used to discharge the main sphere
#     spark produced by the difference of potentials
And the three other languages agree with this. 
Basically, someone tried to match the text with the illustration, adding the numbers to the article, then maybe someone else noticed discrepancies and tried to fix them by altering the legend under the illustration, but it's still not correct. Seems the best thing to do is change the text so first a "statically charged" one like in the drawing is explained, with corresponding numbers, right charges etc.., and with the original legend under the picture. and describe the "electrically" charged one in the next paragraph, the one that currently reads:
:Another method for building Van de Graaff generators is to use the triboelectric effect. The friction between the belt and the rollers, one of them now made of insulating material...
84.197.178.75 (talk) 14:34, 8 March 2012 (UTC)
thread_title:  contradiction in Description section. 

message: Wikipedia:Administrators' noticeboard/Edit warring#User:Менде Фёдор reported by User:Guy Macon (Result: ) --Guy Macon (talk) 19:23, 10 June 2017 (UTC)
thread_title:  Edit war 

message: The figure showing the charges on the rubber belt is still not correct. For the acrylic roller being the one on the top, as shown in the figure, this roller will acquire a positive charge (as shown in the figure) due to the triboelectric effect. This will cause negative charge to get sprayed onto the outer surface of the belt as it passes below the top electrode sprayer (and thus the dome becomes positively charged). The belt thus descends with a strong negative charge on its outer surface, on the right (descending) side of the belt (assuming that the belt is turning clockwise, as shown in the figure). This charge is mainly removed by the electrode charge sprayer at the bottom, so that the charge on the outer surface of the belt is minimal on the ascending (left) side of the belt.  The entire inner surface of the rubber belt will acquire a negative charge from the triboelectric effect, but the corresponding charge density is weak due to the large surface area of the belt (compared to the roller), and this charge thus plays no important role. More details may be found in the following reference: http://amasci.com/emotor/belt.html 2600:1700:12B0:2FC0:DD5:6AA9:1D5B:9722 (talk) 22:52, 14 March 2023 (UTC)
thread_title:  Charge on Belt