electricity question

[Finial]

Can some powerful brain explain something simple for me?

I think (or at least hope) I understand that the live wire brings the current from the power station and the neutral carries it back to complete the circuit. But if that is right, what is the meaning of live and neutral with AC? When the polarity reverses, why doesn't the live become neutral?

 

[Grinding One]

AC is alternating current
DC is direct current---Battery type
generating Stations put out 33,000 volts into a Transformer- the windings in the transformer determine the out going voltage .In the USA its called High Line Voltage or 765,000 volts(Our largest line here)when it has to be used it is stepped down into another transformer to usable voltages .Here that 7200 volts ,stepped down to 110 phase to ground,220 phase to phase.Anything not used goes back to the station on the Ground Neutral System.You can put your tongue on a neutral and nothing will happen but if you break the wire and get between the two ends your dead.
Polarity goes back and forth in cycles here it 60 cycles it happens so fast you cannot see it some say you can feel it,I never did but still its said if you get on the wrong cycle it pulls you in(Muscles contract) other wise it blows you away.I was blown off wire a couple of times,never pulled in,if you do get on good your usually a crispy critter(smoking)& possibly dead.Neutrals kill more people then phases here.

 

[Racers]

Hi,

The Neutral is connected to earth at all the transformers in the supply chain. The current does flow from neutral to live during the negative half cycle of the mains but because it’s earthed it does not change potential in respect to earth.
And what’s even stranger it they guessed the direction of current flow and they got it wrong it flows from negative to positive.

Pete

 

[Grinding One]

Hi,

The Neutral is connected to earth at all the transformers in the supply chain. The current does flow from neutral to live during the negative half cycle of the mains but because it’s earthed it does not change potential in respect to earth.
And what’s even stranger it they guessed the direction of current flow and they got it wrong it flows from negative to positive.

Pete

And thats why if your in an Airplane above the clouds you see lightning going up.

 

[devonwoody]

Hi,

.

Pete

And thats why if your in an Airplane above the clouds you see lightning going up.

Unless you are flying upside down? :x

 

[Grinding One]

Hi,

.

Pete

And thats why if your in an Airplane above the clouds you see lightning going up.

Unless you are flying upside down? :x

In which case you should be running for a hand on the controls...someone has fallin asleep

 

[Finial]

The Neutral is connected to earth at all the transformers in the supply chain. The current does flow from neutral to live during the negative half cycle of the mains but because it’s earthed it does not change potential in respect to earth.

Pete

I forgot the neutral is connected to earth. But when the current is coming in on the neutral, why doesn't it go direct to earth? Is it going out through the earth as well and going back through the live?

 

[CHJ]

Is it going out through the earth as well and going back through the live?

No they (neutral and earth wires) are, or should be, the same potential so no pressure to cause a flow.

In an Ideal world there should be no current flow in an appliance Earth wire, it should be the same potential as the Local soil and providing a shield around the power consuming components.*

Current is coming and going in the Neutral line, which in an ideal world would be the same potential as the Ground(The Earth), in practice the current flowing through the Ground would be constantly variable due to the differing resistance of soil/rock/water etc. so a Neutral circuit wire has to be taken back to the generator.

The fact that there is a parallel route for flow of current through the Ground/Soil/Earth is the reason that Residual Current Circuit Breakers work.

If a current flow gets partially diverted via the Ground(soil/earth) so that the current in the Live and Neutral lines to an appliance do not balance then the device assumes that a fault is occurring (someone has stuck their finger where it should not be) and turns off the supply.

* in practice a small current flow can often be found in an appliance earth wire due to interference suppression components fitted to motors and switches and induced current due to cross linking, in household systems using older technology Earth Leakage Protection Units (overhead wire supply) where the earth wire cannot be guaranteed this leakage can be enough to keep tripping the system.