# Static electricity with spinning disks

1. Apr 26, 2004

### Jdo300

Hello, I am working on a project involving static electricity. I am trying to build a motor type device that can accumulate a static charge through two disks made of dissimilar materials (I’m still working out which two materials would be best) spinning past each other in close proximity. I’m wondering if it is possible for a static charge to build up on the two disks if they are spun close to one another (say with about 1/16 in separation between them. Or do the disks have to be touching/sliding on each other for this to work? I would like to use smooth materials for this experiment. Could someone please enlighten me on this?

Thanks,
Jason O

2. Apr 26, 2004

### wolram

3. Apr 26, 2004

### Jdo300

Thank you for the reference. What I am working on is vaguely similar to a Wimherst machine. My question is answered about weather the disks have to be in contact (they don't) to generate a charge, right?

Well, I have a few other questions as well. If I were to use two solid disks spinning close to eachother, only facing horizontally one above the other on a vertical shaft, and I had the top disk magnetically levitated above the first, when the static charge builds up, would there be any kind of mechanical friction that would try to slow down the movement of the bottom disk? In this example, I plan to rotate only the bottom disk and fix the top one to the shaft (which is also non-moving). My idea is to eliminate as much friction between the two disks as possible. I know that the disks will want to attract eachother when they become charged, but as far as rotational force goes, what they be slowed down from the static charge present? Also one more thing: would the presence of permanent magnet fields have any effect on the charge buildup on the disks?

Thank you,
Jason O

4. Apr 27, 2004

### wolram

5. Apr 27, 2004

### Jdo300

Thank you for the resource link. It looks like I need to do more reading up on the Wimherst and other electrostatic machines. I'm not sure but I think what I am trying to make is similar to an influence electrostatic machine. The whole idea is that I don't want any parts rubbing, rolling, or brushing up against each other to create the charge. Would that be the correct definition of an influence machine?

Well, I came up with yet another question, and this one I have had some trouble finding information on. Perhaps someone here could help me out I'm wondering if it is possible to induce a static charge using a permanent magnet. (Ex: spinning a disk next to the pole of a magnet). Would that cause charges to collect?