Electron Movement in a Dielectric

Understanding how electrons move through and interact with a dielectric material is instrumental in understanding capacitance or gravity. When electrons are more plentiful and active voltage is found to be more negative. The more negative voltage area is going to have electrons emanating from it. These electrons will fly relatively fast and straight. A dielectric material will backfill the fast electron with an electron moving in a more erratic manner.

There is a lot of space between atoms in a medium. This allows electrons moving from a more negatively charged region to a less negatively charged medium. The atoms the electron passes along the way may give up electrons to backfill the fast electron that blew past. How fast this backfill process happens depends on the root mean squared speed of electrons at that point in space. 

Electron movement is generally more ordered when an electron moves from negative to positive. This is because there is generally a lot of space between atoms.  Less ordered is the movement when moving from positive to negative. This is because the electrons will wander back at the local root mean squared speed to backfill a fast moving electron going from a more negative environment to a more positive environment. Electrons shoot one way and bubble back to fill the charge balance from the electron that blasted away.