AC Current versus AC Voltage on the Neutral Wire of AC Mains

[Sarrah]

Homework Statement

AC Current

Relevant Equations

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Sir how can one explain with the help of an analogy to a grade 10th student the reason behind not getting a shock on touching the neutral wire of the household AC circuit, even though the current flows alternately through live as well as neutral wires.

 

[berkeman]

Problem Statement: AC Current
Relevant Equations: -

Sir how can one explain with the help of an analogy to a grade 10th student the reason behind not getting a shock on touching the neutral wire of the household AC circuit, even though the current flows alternately through live as well as neutral wires.

I am not familiar with the home AC Mains electrical codes in your country. In the US, Neutral and Earth Ground are connected by Code at the home distribution panel, so there is very little voltage developed between Neutral and Earth Ground within a home. (Safety Note -- that assumes that the home has been wired to Code, and there are no faults in the system -- it is always a bad idea to use a human as a "shock/fault detector"; I hope you realize that.)

Can you post the relevant Code regulations for the country where you are teaching these students please? In the US, the Code requirements are published in the NEC.

 

[berkeman]

And to add a very important safety note, when you say "touch" and "shock", you need to also mention what else the test dummy (literally) is touching. A bird on a high voltage wire will not feel a shock, because it is just sitting on one wire, with no other voltage references. A (stupid) person touching only a Hot or Neutral wire alone and nothing else will likewise not feel a shock.

But a person touching a Neutral wire and a Hot wire is risking their life, due to the large shock that they will experience. I once had a very discouraging discussion with a very experienced carpenter who tried to convince me that a GFCI would protect you if you grabbed Hot and Neutral in your two hands. I tried my best to explain to him how GFCIs only protect against faults from Hot to Ground, but he was having none of that. Hopefully you are smarter than that.

 

[lomidrevo]

In normal situation, current flows through the neutral wire only when the loop is closed, i.e. when electrical appliance is connected (to hot wire also). In any case, touching the wires is strongly not recommend!

 

[Sarrah]

I am not familiar with the home AC Mains electrical codes in your country. In the US, Neutral and Earth Ground are connected by Code at the home distribution panel, so there is very little voltage developed between Neutral and Earth Ground within a home. (Safety Note -- that assumes that the home has been wired to Code, and there are no faults in the system -- it is always a bad idea to use a human as a "shock/fault detector"; I hope you realize that.)

Can you post the relevant Code regulations for the country where you are teaching these students please? In the US, the Code requirements are published in the NEC.

View attachment 243458

Please explain as per your country's norms.

 

[haruspex]

Problem Statement: AC Current
Relevant Equations: -

Sir how can one explain with the help of an analogy to a grade 10th student the reason behind not getting a shock on touching the neutral wire of the household AC circuit, even though the current flows alternately through live as well as neutral wires.

The principle is that neutral stays at roughly Earth voltage while the line(s) vary relative to that.
As has been noted, this means that the neutral is in fact earthed at intervals in the distribution. Correspondingly, the power station is earthed on one side. Only the lines run on wires to the grid.
If there is a high current, I, on the circuit at the house then the voltage on the neutral can deviate from Earth by IR where R is the resistance of the neutral wire from where it is earthed to where you are touching the neutral. There is always the risk of a short, leading to a very high current and perhaps a dangerous voltage on the neutral. (And by resistance here I should include capacitative/inductive loads.)