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Mains = Active - Neutral - Earth
Lets split answer into two:
- current from Active through a load and Neutral travels back to the nearest step-down mains transformer, where the loop is closed; if not for that transformer it would go back to the power generator ..
- Earth/Ground; in ideal situations no current should flow through the Earth wire; it is provided only for safety reasons and is connected to the local Earth just outside of your building, quite often connected to a copper rod hammered into ground and/or watter supply pipeline ..
The above arrangement may vary from country to country and depends on the local regulations ..
Good question. Neutral is connected to "earth" at the power station for safety reasons. The power system is not isolated from earth but there is a very solid earthing (grounding) at the power station. Also ground is connected to earth outside your building. So the loop is closed between one end- the "live"or "mains" of the power generator at the power station (or the high/medium voltage transformer of the power company that also has its neutral connected to earth), the cabling to your house, the leak, the grounding scheme at your building and the grounding arrangement at the power company connected to the other end of the generator (or transformer) named neutral.
Of course this is simplified because 3-phase power is used but still neutral is earthed by the company. Many years ago neutral was also connected to earth at each house but this scheme has been abandoned and is against the regulations of most countries.
There is normally some ground current through the ground electrode at the neutral main. The current is much smaller than the neutral current. The neutral provides a very low impedance path back to the generator, however the ground provides another high impedance path back to the generator. Ultimately, the current provided by the generator must flow back, but electrons don't care much about the path and will take every path back to the generator in proportion to the admittance of that path.
The purpose of the ground electrode is simply to remove the step potiential between the neutral and the ground near the ground electrode. Without the ground electrode, you cannot guarrantee the potiential of the neutral is at zero volts relative to ground.
The ground potiential actually varies from place to place. Large ground currents have been recorded in the crust of the earth. The magnetic field of the earth itself can be explained by large currents in the earth (most people think in the core and mantle). Basically, however, this is a hypothesis and no one really knows the entire nature of the magnetic field or the currents in the earth. I read an article that earthquakes may be detected by measuring ground current and potiential (in reference to what?) and radiation due to corona discharge from the ground to the air.
Anyway, I ramble because I have more questions than answers but perhaps this helps some: for every amp that leaves one terminal on the generator, an amp must enter the other terminal and current flow through the surroundings is dictated by the resistance of paths between the terminals (some electrons even wander the gap through the air from one terminal to the other, however, these would be rare indeed).
it goes no-where...strange huh...!!!
i explain it..
the ground terminal or the neutral, the positive terminal..all these are used to produce thrust to move electron..and when electron moves, current is produced.. so, the kinetic energy of electron is shaped into electronic current..
as i said current goes nowhere..because the electron remnains within conductor, it don't leave it..
rememeber that that the actual flow is from Ground(or neutral) to the positive terminal..we use convention that the current flows from positive terminal to Ground(or neutral)
In North America standard "mains" power was two-wire (hot and neutral) in many places. Within the last 50 years, the standard has gone to 3 wires, hot, neutral, and ground. The reason was mainly for safety. The replies before correctly state that any current flows between the hot, through the load, to the neutral, and then the reverse, mains being AC power. Since many machines include electric motors, to prevent shock from these machines the machine frames are connected to the ground wire in the mains circuit. If the motor winding shorts to the frame, for example, theoretically any current will flow through the ground wire and not through any person who happens to be touching it. You'll probably notice that most power tool bodies today are made from plastic and not metal as in the past. In addition to being more economical, the plastic bodies insulate the user from the power line. Whereas any device that has a metal housing is required to have a 3-wire grounded plug, plastic-housed devices are not, and commonly use a 2-wire plug. So if the power circuit and load are functioning properly, there should be no current flow through the ground wire.
The Current gets a closed loop in the ground ........and whenever there is a closed loop shall the current be able to flow..........The direction of the flow depends on the voltage difference...........the current always flows from a high voltage point to a low voltage point !!!...........(remember diffusion )