Ohms law in theory and practice

[JohnW2]

Surely a neutral conductor is always earthed, otherwise it ceases to be a neutral conductor.

Not at all - It would still function as a neutral without being earthed. Norway uses such an arrangement, for example.

I'm a bit uneasy about this off-topic stuff confusing the OP but, anyway, my understanding was that Norway utilises IT with no neutral conductor (just two phase conductors) being provided to single-phase installations (and just the three phases to 3-phase ones) - is that not the case?

Kind Regards, John.

 

[ant101]

Think Im getting there. No doubt youll here more from me soon.
Thanks for your time.

 

[Space cat]

I'm a bit uneasy about this off-topic stuff confusing the OP

Agreed. That's why I didn't expand on the difference between impedance and resistance.

Ant101, by now you will see that the definition of "neutral" is not clear cut but one thing remains true: "NEUTRAL" does not mean "SAFE".

 

[Paul_C]

my understanding was that Norway utilises IT with no neutral conductor (just two phase conductors) being provided to single-phase installations (and just the three phases to 3-phase ones) - is that not the case?

I believe that is so for many supplies, i.e. it's 220-230V between phases, unearthed and with no distributed neutral, and possibly supplied from a delta-connected secondary. But I've also seen references to a 230/400V wye system being used with unearthed neutral - I think it might have been in some of the Schneider documents. Either way, a 3-phase wye system with unearthed, distributed neutral is possible.

To look at this from a slightly different perspective, in North America there can be found a configuration known as corner-grounded delta, so that in normal operation one of the three phases will be at or near earth potential, and thus just as safe (or unsafe, depending upon the circumstances) to touch as an earthed neutral.

Even if not following all of these details, I think the key point for the original poster to recognize here is that whether touching any particular conductor will result in a shock or not (assuming that the circuit is completed through the body to earth) depends not specifically upon whether it's a neutral conductor or not, but upon the voltage on that conductor relative to earth. It's just that under normal operating conditions the neutral on a U.K. LV public supply will be at (or almost at) earth potential.

 

[JohnW2]

Even if not following all of these details, I think the key point for the original poster to recognize here is that whether touching any particular conductor will result in a shock or not (assuming that the circuit is completed through the body to earth) depends not specifically upon whether it's a neutral conductor or not, but upon the voltage on that conductor relative to earth. It's just that under normal operating conditions the neutral on a U.K. LV public supply will be at (or almost at) earth potential.

Yes, in the context of this thread, I think that's the important point. In fact, as I'm sure (s)he would recognise, the first thing that ant101 probably needs is to get a clear understanding of the most basic concepts (per the thread tile, I suppose) about voltage, current and the relationships between them - conceptually, as well as in terms of Ohm's Law.

Kind Regards, John.

 

[ban-all-sheds]

• http://www.google.co.uk/search?q=electrical+circuits+101
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/electricity.html

 

[ban-all-sheds]

Edit: The connection from neutral to earth probably isn't in your house; it'll most likely be at the substation.

PME?