Attracting small splinters of glass with a Van de Graaff generator

  • #1
Hello,

I work for a container factory where re-used bottles have a lot of tiny glass splinters. Inspired by the standard experiment of picking up glass splinters using a comb, I thought I could insert a charged rod into a bottle to attract little splinters towards it. To get similar voltages as a comb, I bought a small tabletop Van De Graaff generator.

I took a rod, connected it to the VDG sphere, and tried placing a few splinters close to it. The splinters don't seem to get attracted to the rod in any consistent way. Some of them 'orient' themselves towards the rod, but don't move towards it. Some touch the rod and then repel. I don't know how to proceed from now - could anyone please throw some light on this? My ultimate aim is to get rid of the splinters in whatever way possible.

I'm new here, so please let me know if I should re-post this in a more appropriate sub-forum. Thanks a lot in advance!
 

Answers and Replies

  • #2
ideasrule
Homework Helper
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Hello,
I took a rod, connected it to the VDG sphere, and tried placing a few splinters close to it. The splinters don't seem to get attracted to the rod in any consistent way. Some of them 'orient' themselves towards the rod, but don't move towards it.

That's because the rod isn't charged enough for the splinters to overcome the friction of the surface they're sitting on and start moving towards the rod.

Some touch the rod and then repel.

That's because when the splinters hit the rod, the charge on the rod tries to spread out across the splinters. The splinters will then have the same charge as the rod and repel it.

I don't know how to proceed from now - could anyone please throw some light on this? My ultimate aim is to get rid of the splinters in whatever way possible.

What's wrong with filling them up with water, giving them a good shake, and dumping out the water? That seems fast and reliable.
 
  • #3
Thank you for the quick reply, I was suspecting the low charge magnitude and the charge transfer were causing these problems.

That's because when the splinters hit the rod, the charge on the rod tries to spread out across the splinters. The splinters will then have the same charge as the rod and repel it.

Would it be possible to shield the sphere in some way so that the splinters do get attracted to it, but there is no charge transfer (and so no repelling, so they will stick to it)? I tried a plastic and paper coating, but that did not work.

What's wrong with filling them up with water, giving them a good shake, and dumping out the water? That seems fast and reliable.

That is a nice idea, and we have a similar system working with a jet of air. The problem is that this severely limits the rate of bottle production. We have rates in excess of 60 bottles a minute, so this causes problems.

Please let me know if there's anything else you have in mind, as I'm really stuck with this :(
 

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