why is it logical to say that potential of an earth connected object is zero?what can be said about the charge on the earth?

Question

anonymous · Answer

Simply put, the Earth is so big that any charge you try to fill it up with to give it a charge will not affect it's charge density.

anonymous · Answer

It's not logical at all, but it is reasonable.  It's reasonable because nearly everything that we'd like to regard as "neutral" is in contact with the Earth, or was a little while ago.  The most common electric potential of objects on the surface of the Earth is, for obvious reasons, equal to the electric potential of the Earth itself.  We might as well define that as zero, and measure everything from it.

What is it, really?  Who knows?  We'd have to go somewhere else in the universe, connect wires to the Earth, and see which way a current flows, if there is any at all.