Though EE was the best section but if not I'll repost or get a mod to move it. We were learning about Electrostatic precipitators that are used in power stations and the like to remove dust particles from the smoke they release. However in the diagram that our teacher had it just showed the metal grid and then the plates above them. And he said that the grid is positively charged and the plates are negatively charged and as the dust particles pass through the grid they become positively charges and are then attracted to the negative plates where they lose their charge and fall down. Now I've seen these things before at a trade show my dad took me to and at the trade show the demonstrator was talking about positive corona discharge around the plates and the effect it has of ionizing the air and dust and then its attracted to the negative corona around the plates. So I said to the teacher and he basically said that no corona discharge should occur as there should be no arcing between the grid and the plates?