A question about electrical ground (with diagrams)

[jim hardy]

This "infinite Sink" concept i think comes from thermodynamics where there is an infinite heat sink.

There is no infinite "charge sink" that i know of.

In your earth-moon-lightbulb experiment try this thought: (EDIT - oops i forgot yur battery. Kindly reconsider the experiment with no battery)

Earth and moon have some finite area facing one another and are separated by what, 240,000 miles of free space?
So they have capacitance of [free space permittivity X that area / 240,000 miles X some weird units converter constant] farads. Your light would illuminate until that capacitance is discharged.
How it got charged to begin with is a mystery to me. Some geologists think the moon was once the floor of Pacific Ocean, maybe it took some charge with it when it left. Do you suppose a few electrons came back with Apollo astronauts ? (EDIT - maybe it was you left it at 50 volts ! That's a he-man toy you got there, dude !)

Kirchoff's current law says basically charge gets back to where it came from.
In the case of static electricity Kirchoff will accept a temporary delay.
This is exemplified by lightning. Charge is swept upward from Earth but comes back with a bang.
Consider the parallel with water - it evaporates from oceans rains on the hilltops and runs back into ocean. (Just watch the pretty Weather Channel ladies showing satellite pics of clouds sweeping up from Gulf of Mexico across Tennessee Valley and on up to New York) .

Basically Earth is just another wire. But it goes everywhere on the planet. And like any other wire there'll be some voltage drop wherever current flows along it.

I think we are imprinted early in life by lightning to think of Earth as somehow attracting electricity. Some folks won't even set a car battery on the ground.

hope this helps.

old jim

 

[nausher]

Ordered Chaos - I really liked your diagrams, and I had the same exact questions to begin with.

After reading all the replies I understand -
(i) An AC Circuit needs to be complete before the current will pass through it and light up the load (Light Bulb).
(ii) The Earth 'can' be used to complete the circuit, and if it is, the light bulb will still light.

My open question is if the Earth (a) 'can' be used to complete the circuit or
(b) 'should' / 'is normally' used to complete the circuit. I am not clear as to which of these is right.
Or in other words, in a regular home circuit with 2 prongs ('hot' and 'neutral') does 'neutral' go back to the transmission system to complete the circuit or does it go to the earth.


PS: I also read up a bit at the following sites which helped somewhat, but they are all missing a simple circuit diagram,
showing where 'Hot' , 'Neutral' and 'Ground' go to (i.e Either back to the Transmission system or to Earth)
http://amasci.com/amateur/whygnd.html
http://electronics.howstuffworks.com/everyday-tech/question110.htm

PPS: I do understand that for the purpose of protecting the innards of metal covered appliances the metal cover needs to go directly to the earth.