The Physics of a Van de Graaff Generator
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- čas přidán 11. 07. 2024
- This short animation describes the physics behind the Van de Graaff Generator.
A Van de Graaff Generator makes use of the Triboelectric effect to transport electrons from a source to a sink, generating a large potential difference in the process which can result in a spark.
Narrated by Muhammad Omar and animated by Nasir Yousufi.
0:00 Introduction
0:24 Triboelectric effect
1:23 Anatomy of the Generator
1:53 How it works (at the bottom)
3:05 How it works (at the top)
4:22 What causes the spark?
4:51 Overview
Disclaimer: image of Robert Van de Graaff by Suaima sourced under the Creative Commons Attribution-Share Alike 4.0 International license.
commons.wikimedia.org/wiki/Fi...
Man that was fantastic! I was loving everything. Terrific explanation. Clearest and most understandable one I have ever seen. Keep it going!
Awesome, thank you!
Finally, I can rest in peace!
This has to be the most beautifully explained amongst all others
Well thank you very much! I'm glad you found it so useful
Thx for such a clear explanation!!
Loved the way you talked bout them
Perfect explanation with precise graphics and clear voice.
Thank you. I finally understand how this thing works after an hour of researching. Brilliant explanation.
My pleasure!
i watched multiple vidoes before this one in order to understand how VDG works and this was the video that worked for me. Thank you!
i watched many videos and read many articles about this but i found yours the most helpful among them all! tysm i finally can grasp it hahaha
Perfectly explained. Thanks a lot🎉
I truly look up to you. explaining something complicated in a way that anyone can understand is a skill I strive for.
Thanks for the kind words!
If it helps, I find that giving your explanations an underlying structure makes it easier to understand without having to oversimplify things. I think it allows people to better organise the information they're receiving, making it easier to learn and then later recall, as well as make connections to other things. That's the idea atleast!
You are the best teacher, ever!
Amazing man I love it❤
After a long hours I finally understood the mechanism of this device, thanks a lot :)
If you understand then explain to me How can the under spikes be positively charged if the rod attached to it has negative charge?
Soo effective .Thank you.
Thanks, mate! When I can't sleep I play your video and before the end of it I'm in dream-land ;-)
Thanks! Glad you like it
Muito bom! Obrigado!
Thanks for the help
Nicely explained
Super!
Superb
Lovely work!
Thanks
Many thanks for your effort.
No problem
Clear explanation
very nice
this explained it a million times better than my teacher
Thanks for this wonderful video and God bless.
Also, why does the negatively charged bottom roller and positively charged belt not balance out by a spark? For example if one is +ve and other -ve, they should produce spark and equalise electrons?
Thankyou
Definitely the best video, but I still have one question. When the belt becomes positively charged at the bottom roller by the triboelectric effect, why do the positive ions stick to the already positive belt? Shouldn’t the belt repel the positive ions despite the attraction of the roller? The belt is closer to the ions after all.
Well done, I've wanted to build one just for the fun of it. Did you do the animations in blender?
Yep. Animation and video editing. It's a very versatile software.
I'm not sure I understand the balloon example. I get that the balloon gets electrons, and becomes attracted to the protons in wall. But wouldn't it be equally repulsed by the equal number of electrons in the wall?
Ok I think I figured it out. I should've watched more before commenting. Just like in the other examples, the negatively charged ballon repels electrons in the wall.That makes the wall positively charged. and then that attracts the negatively charged balloon.
Yes exactly, you have the right idea!
The atoms/molecules of the wall are overall electrically neutral, but in the presence of an electric field the electrons will shift slightly and separate from the positive nucleus (this is called polarisation). The negatively charged balloon provides this electric field, repelling the electrons in the wall and leaving behind the positive nuclei.
This same effect can explain a lot of molecular forces (e.g. the electric field from a charged molecule polarizes a nearby neutral molecule and they attract) and is used when designing capacitors (a material placed between two oppositely-charged parallel metal plates gets polarised by the resulting electric field - the electrons are shifted one way, the nuclei go the other way).
It's good that you raised the question as I'm sure this helps clarify things for other people too!
do you think it's possible to make the belt using Teflon and the roller using PVC, Will it work?
I don't think so because the belt has to both gain and lose electrons, so the materials for the two rollers need to be above and below the belt material in the triboelectric series. Teflon is already really low down in the triboelectric series, so I doubt you'd find a material even lower than that for one of the rollers.
From what I've seen online, Teflon and PVC are very close, so you could try it out. Just make sure the two rollers are of different materials above and below Teflon e.g. PVC and glass
@@mr.nofear8646 thanks alot!
How can the under spikes be positively charged if the rod attached to it has negative charge?
You're asking how the same object can be both positively and negatively charged?
Initially both the rod and metal spikes are neutral. As the bottom roller builds up negative charge, this repels electrons at the tips of the metal spikes and they move down to the rod.
So the electrons have flowed from one area (spikes) to another (rod), leaving the spikes with less electrons (positively charged) and the rod with more electrons (negatively charged). Hopefully this makes sense.
🎉⭐⭐⭐⭐⭐
Help.
The mechanism seems exactly opposite of the hair and balloon. If a balloon becomes negative after friction with hair why doesn't the rubber belt become negative when run against the felt rollers of the Van Degraaff? Straight to the point, I was always under the impression that the dome became more negative and not positive.
Whether the dome becomes positively or negatively charged depends on the materials used and their relative positions on the triboelectric series.
The balloon becomes negatively charged because rubber is lower down on the series than hair and thus has a greater tendency to gain electrons.
However, the rubber belt becomes positively charged because the bottom roller is made of Teflon which is lower down on the series than rubber, so Teflon has a greater tendency to gain electrons than rubber (so the rubber belt loses electrons).
Compare that with the top roller which is made of aluminium, which is higher up on the series than rubber, so has a greater tendency to lose electrons than rubber and is left positively charged (while the rubber belt gains electrons).
In this setup, the dome becomes more positively charged because the top roller loses electrons, but if you swapped the two rollers around, then the bottom roller (aluminium) would lose electrons, and the top roller (Teflon) would gain electrons, causing the dome to become more negatively charged instead.
You can use other combinations of materials too; as long as you know where they are on the triboelectric series, you can figure out where the electrons flow.
Hopefully that clears things up
@@mr.nofear8646 ok. That helps quite a bit. The one I teach with has a felt bottom roller and a plastic of some sort up top.
Thank you
That's interesting. So presumably the felt roller would lose electrons, which ride up the rubber belt and are then gained by the plastic roller, giving it and the dome a negative charge.
If you have an electroscope you should be able to find out the polarity of the charge on the dome. I suppose you could also charge up a balloon by rubbing it on your head and then hang it by a string near the dome. If it's repelled, the dome is negatively charged; if it's attracted, the dome is positive.
Glad I could help
@@mr.nofear8646 I always hang a balloon from the classroom ceiling. When the kids stand next to the generator I always have them reach out to the balloon to repel it away.
I also have them reach for a thin board that I mounted to a fidget spinner. They are able to attract the board with their hand like the balloon to the wall.
Why is the negative pole a sink when electrons are moving to the positive charge and the pole is the source of the electrons
A sink is the opposite of a source.
The dome acts as the source of electrons as it supplies the electrons - as electrons are removed from it, it becomes positively charged.
The metal rod acts as the sink as it takes up electrons - as electrons gather on it, it becomes negatively charged.
Electrons are moved from the source (dome) to the sink (rod) by means of the belt carrying electrons down the column.
During the spark, electrons move from the negative metal rod to the positive dome, so the rod is now acting as the source and the dome now acts as the sink.
Hopefully this all makes sense.
what if the spikes touch the belt?
I don't know exactly - the device probably wouldn't work as well. Presumably there would be another triboelectric interaction as the belt rubs against the spikes, I guess depending on which material is used for the spikes.
The device relies on the belt losing electrons at the bottom and remaining positively charged on its way up to the top where it collects electrons from the dome and brings them down. So if the bottom spikes lose electrons to the belt, this could reduce the size of the positive charge carried up the belt, impeding its ability to charge up the dome.
If the bottom spikes instead gain electrons from the belt, this might interfere with the roller charging up, but maybe not since I don't think there are many metals lower down on the triboelectric series than Teflon.
If the top spikes gain electrons from the belt, this would leave the belt even more positively charged, rather than it taking away electrons from the dome.
If the top spikes lose electrons to the belt, I think the device should still work, maybe more slowly.
There may be other phenomena that occur too with all the interacting electric fields, but this is my best guess for now.
So.. it flings electrons
Depends on how you think about it I guess, but it's more accurate to say its like an electron vacuum sucking them out of the air till the bin is full and needs emptied
@@theamaturepro I think flinging is better
@@xlargetophat 😂 then flinging it is! I actually like it.
@@theamaturepro the centripetal force is overtaken and the electrons are flung out. The curve seems important.. idk.. maybe not because maybe the curve only exists because of the form factor of the machine. I guess the electrons would leave if the copper pickup was a long the sides as well.. but maybe the roller it self being Teflon does the pushing and the curve doesn't matter at all? Idk
@@xlargetophat oh, are you talking about the belt flinging electrons? That totally makes sense. I thought you meant the sphere. Also, nice use of the term centripetal. You've obviously taken physics
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