When an emf is generated in the alternator both poles are simultaneously 0V or at polar opposites in varying degrees of voltage. However in the supply circuit the live is +tve or -tve in varying degrees of voltage & the neutral remains at 0V.

So the question is, what happens after the alternator? In the supply circuit, the live seems to represent one of the alternator poles, whilst the other pole is seemingly converted to create a 0V neutral path.

Many thanks.

A neutral, technically referred to as the grounded conductor, is created by intentionally grounding, or connecting to earth. The same current flow of the supplied load can be measured in the "neutral", however voltage is measured to ground will be at zero.

Does this answer your question?

Thanks for the reply.

In my minds eye I see a simple alternator, the two poles of the rotor are connected via the slip rings to two conductors. Are you saying that one of these conductors is connected to an earth terminal whilst the remaining conductor is the functioning live? Or is it more sophisticated than this?

Perhaps I should try to find a wiring diagram of a generator which shows the two conductors at one end & the live & neutral supply connection at the other.

While utilities providing homes and business create power using alternators, the grounding is not usually done at the source, more done at step down transformers located closer to the consumer, and the neutral is created at that point for the wiring in a building.

However, if someone where to buy their own generator, (we still call them generators even thou they are actually alternators) at that point, the neutral is grounded.

A grounded conductor is required in buildings for safety, and reliable operation
Of overcurrent protection devices. Not so important for high voltage long line transmission lines.

No electrical circuit has by nature a "neutral".
Every electrical circuit has just two or more points that differ in voltage.
If you take a battery, there is no neutral. Just two contacts.
A transformer - depending on the internal wiring - may have a common contact that is called a neutral (with 2 or 3 phase voltage supply).
A neutral is "created" if one of the points in a circuit is either common to other circuits or to "earth".
.
In the main power supply to your home, a neutral is created in the utility transformer that brings the voltage down to that you are used to at home.
Depending if that neutral is connected with earth or not, the neutral is either really without any voltage related to earth, or very near to that of earth.
The power consumption from such a transformer may cause an electrical imbalance, with the neutral fluctuating around that safe earth nil voltage.
In an alternator circuit the voltage is coming from the generator coil(s) via a rectifying circuit. Normally the negative output contact is connected to neutral or earth.