what is the potential difference of AIR GAP????????
A charge distribution or configuration throughout vaccum/air medium in given region, will have potential difference across any two selected points in the region.
The potential difference across an air gap has no meaning unless and until the the charge configuration at the to sides of AIR GAP is specified, and it'll be same without air gap, since vaccum and air has the same permittivity.
You have rated this answer /10