# A.C Neutral.

Discussion in 'General Electronics Chat' started by Arsalan Raghib, Jun 1, 2014.

1. ### Arsalan Raghib Thread Starter New Member

Mar 21, 2013
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If A.C (alternating current) changes its direction it means that both terminals should be phase. but there is always a neutral in A.C which is the returning path for current. I want to ask why there is a neutral in A.C? Does it also has a polarity when A.C changes it's polarity?

Jul 18, 2013
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In a single phase supply, the neutral is just another name for essentially the same conductor, it also applies either to the star point of a star connected 3ph transformer grounded or not, or any grounded conductor of an AC supply.
If you have a AC supply fed from a single phase isolation transformer both conductors are considered identical, it is arbitrary which one you earth ground and make 'Neutral'.
Max.

Aug 27, 2009
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4. ### #12 Expert

Nov 30, 2010
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"Ground" is a convention (an agreement) about declaring a convenient place to reference your measurements. "Neutral" is a type of declared ground that has particular properties like being connected to the Earth. The current changes direction, but the voltage at the declared ground is always zero because we agreed to do that. It is not about the properties of electricity. It is about an agreement among the professionals.

Jul 18, 2013
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But to reiterate, neutral is not always earth ground, as in the star point of 3 phase supply, it is declared a neutral whether earth grounded or not.
Although in many cases it is also taken to earth ground.
Max.

#12 likes this.
6. ### Arsalan Raghib Thread Starter New Member

Mar 21, 2013
10
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But if we touch the neutral wire we might not get shock but if we touch the phase wire we definitely get a shock. it means that there should be no phase in neutral. then how neutral also has a polarity. and if we ground the neutral then it should remain on 0V. but still A.C changes it's polarity. How is it possible. Plz can you give me video illustrations?

Jul 18, 2013
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Think of it this way, both conductors, live and neutral, start out as identical in nature, i.e. the same current flows in each and alternates direction at the rate of the applied frequency.
Now if you earth ground one of them, this makes this conductor to equal the same potential as yourself.
Nothing else has changed, only the fact that you will experience no effect in contacting one of them (N).
The same current flows regardless of grounding or not.
Max.

Last edited: Jun 2, 2014
8. ### #12 Expert

Nov 30, 2010
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I don't think we have a video production department.

Jul 18, 2013
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Besides I left my rubber soled shoes at home.
Max.

10. ### BobTPH Active Member

Jun 5, 2013
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If one terminal is 0V or neutral, the current changes direction when the other terminal goes from negative to positive.

Bob

Jul 18, 2013
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Define 0v.
It applies to both conductors, either one can be termed '0' or neutral.
The identical current flows in each.
If I supply you with two 1ph conductors, it is impossible to differentiate between the two, even if one was earth grounded or not, if the pair only are read.
Max.

12. ### BobTPH Active Member

Jun 5, 2013
808
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I did, I defined it as the voltage on one of the terminals.

Bob