Question

Why is it logical to say that potential of an earth object is zero?

Answer 1

if you mean gravitational potential energy, you're only really interested in differences in energy between points, so it doesn't matter where you set the zero point.

so for inverse square stuff it is handy to set \(U_{\infty} = 0\) for the maths, and then have negative energy as you approach the source of the gravity

for the linear assumption near the earth's surface you can say \(U_o = 0\) so \( U(h) = mgh\) but you're still really saying that \(\Delta U = m g \Delta h\). It's the differences that matter.

but then again i'm guessing what you are really asking so this might be a load of old crap :-)

Answer 2

Thanks for this info but i am asking for the electric potential?

Answer 3

It doesn't affect charged objects.

Answer 4

Still guessing but it's the same idea of relative values.

If you interested in circuits, then circuits are commonly grounded [hard-wired into the earth] as a safe place for current to flow to in case of a circuit fault. The earth is a conductor (moisture etc) and it is mahoosive so it can take on board charge due to say the potential generated by a power station and fed into homes ...... much as it does when lightening is conducted to earth via lightening conductors.

But as before, it is called zero because it is convenient to do so. Its potential is fixed and it is a universal ref point for eg home circuitry. You could call it anything you like but you'd need to modify everything by ref to that.

if you more academically interested, for potential \(V(r) = \dfrac{kQ}{r}\), with zero being agreed upon as \(V_{\infty}\), maybe you can stuff the earth in there as a point charge with \(r = R_e\) and see where you come out.

Answer 5

"mahoosive" :D

Answer 6

I'm going to assume the poster is 6 feet tall.
That height would have been measured presumably from the soles of the feet.
They in turn, presumably would have bee resting on a flat surface - a "local earth".
Special Relativity aside, you presumably are a very similar height wherever you are. So, against ALL those earths you are still 6 feet.
However, in electricity and electronics where there are circuits involved you can get things called "earth loops" or "ground loops" which can be disruptive, shall we sway.
Or, to put the thing slightly differently ... who says that science is LOGICAL, although I have been exhorted to bellieve that it is !