Can someone explain the charge generation process of a van de Graaff generator?

[sauri]

I am having a difficulty understanding how the van de Graaff generator works. Especially with the charge configuration diagrams. Can anyone help to clear the steps involved with the charge generation process?

 

[abercrombiems02]

A van de Graaff generator has two ends. there's one end towards the top (which is like the sphere) and there's on at the base. Connecting the two ends is a non conductive belt and a non conductive rod (for structure). Initially the entire apparatus is grounded (meaning that there is an equal number of protons and electrons on each end so the net charge and potential is zero). When the device is turned on, the belt is powered like a treadmill. The belt runs over both ends and strips electrons off the top end, these electrons are then carried away as they are grounded when approaching the bottom end. The result is that over a period of time the number of electrons on the top will approach a finite value. Actually, the rate at which electrons are stripped off the top decay exponentially. In the end the top half of the van de graaff is left with a deficiency of electrons and thus a net positive charge. Of course it would be unwise to discharge the van de graaff by then touching it. On the other hand if u keep you hand on the van degraff while it is running from start to finish i will never know the difference other than your hairs popping up. To discharge, simply run the machine very slowly for a little bit. When the device runs slowly, the electrons accumulate more on the belt and are returned to the top half, thus reducing the potential, and the pain that would be associated if u were to immedeatly ground yourself.