# Homework Help: Earthing of a charged sphere

1. Aug 27, 2013

### andyrk

When we earth a positively charged sphere, the positive charge of the sphere vanishes. Why does this happen? When we connect two charged bodies doesn't charge redistribute till we get equipotential surface? Now when there is no charge on the sphere means the sphere has 0 potential. So that means even the earth is taken to be at 0 potential? Is it true? And if yes then why we take the earth to be at 0 potential? Is it because earth is considered to be neutral? Do positive charges from the sphere flow into the ground? Does this mean there is deficiency of positive charges in the earth?

Had the sphere been negatively charged, what would have happened then? Would the electrons would have also flown into the ground? Does this mean there is deficiency of negative charges in the earth?How can earth be deficient in both negative as well as positive charges? If the earth is neutral why would it want negative or positive charges? Does this simply mean that if we connect a charged body to a neutral body body the bodies become neutral? That is, both get potential as 0?

2. Aug 27, 2013

### Staff: Mentor

Size matters. If you take an atom and add an electron to it, you are greatly increasing its energy through the Coulomb interaction. If you add an electron to a conduction sphere the size of the Earth, you are not changing the its energy as much, even if it is already negatively charged, as it has many ways of redistributing its charge to accomodate the new electron. Even if Earth is not exactly neutral, it is an universal absorber/giver of electrons.

If you take two identical bodies and charge one, when connecting them together you will get equal charge on each, mening half the original charge if one was neutral.