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Is the neutral hole socket on the left or the right side? Is this universal to all countries and most houses?

The neutral wire is usually at 0V relative to earth right? Or 0V RMS? HYPOTHETICALLY, if one were to stick a knife into the neutral hole, would they be fine?

Edit: Would the outer-pin of a laptop charger always be neutral regardless of the polarity of wall socket?

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  • \$\begingroup\$ While they might not get electrocuted, I'd consider them suicidal and they should get treated accordingly. And in Germany there is no rule on where neutral goes (as far as I know), so the answer is probably no. \$\endgroup\$ – Arsenal Sep 28 '16 at 13:38
  • \$\begingroup\$ Then the outer-pin of a laptop may be live then? Or does the transformer ensure it is neutral? \$\endgroup\$ – user40300 Sep 28 '16 at 13:43
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    \$\begingroup\$ @user40300: The power supply of your laptop has a mains side and a low voltage side. These two are completely separated. So dont worry. \$\endgroup\$ – Decapod Sep 28 '16 at 13:49
  • \$\begingroup\$ The "transformer" will usually provide an isolated output, so neither pin will be anywhere near live. \$\endgroup\$ – Arsenal Sep 28 '16 at 13:49
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    \$\begingroup\$ @Arsenal how much voltage is the outer pin relative to ground? \$\endgroup\$ – user40300 Sep 28 '16 at 14:26
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The neutral wire is usually at 0V relative to earth right? Or 0V RMS?

The 0V is relative to earth, in theory. When the neutral wire carries some current from devices, the resistance causes a small voltage between neutral and earth.

Besides, RMS does not mean "relative to hot wire". It just tells how voltage is expressed.

HYPOTHETICALLY, if one were to stick a knife into the neutral hole, would they be fine?

HYPOTHETICALLY, yes. Though, don't to this!

Is the neutral hole socket on the left or the right side? Is this universal to all countries and most houses?

Some outlets have a distinct orientation, some have not, like this Type-F used in Germany: enter image description here

There is absolutely no rule which one is neutral and which is hot. It is sometimes said to connect neutral to the left when the outlet is mounted with the holes aligned horizontally, since then it's the same as Type-E, which is used in France, for example:

enter image description here

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  • In North America, Japan and most other countries, Neutral is always Earthed at the D.T. ( Distribution transformer ) ... It also may be earthed at residential plumbing for underground copper pipes.

    • In (most of) Europe 2 of 3 phases and grounded neutral are provide to residents 400/230Vac

    • In America only 1 of 3 phases is used per household and is split with centre-tap neutral-earthed 240/120Vac called L1 & L2 with 240Vac differential or 120vac with respect to neutral, while Europe using 2 of 3 phases the differential voltage is (root3) * 230V = 398Vac approx.

"The purpose of grounding the electrical system as stated in NFPA 70: National Electrical Code (NEC) is, “To limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines that will stabilize the voltage to earth during normal operation.”

Power distribution is regulated in countries with good infrastructure to 5% for transmission load variation and 5% for distribution.

In split phase delivery in America, since Neutral carries the return current for both L1 and L2, the voltage drop is expected to be less or near zero, if they are balanced. If notm then an voltage difference drop of up to 5% can occur when the breaker panel is loaded on one phase only with I^2R voltage drop from this imbalance.

We do not see much here, but your location is different.

Appliances using a 2 pin plug must be "Double insulated".

The possibility for Neutral to rise with lightning transients is greater with exposed power lines.

However that being said, there are line filters which conduct EMI noise pulses to ground to reduce interference and on laptops this ground barrier stops in the external battery charger and is not passed onto the laptop case ground, so the laptop is "floating" and limits ground current from lightning transients by the quality of the insulation.

i.e. your laptop is never grounded, unless you connect it externally.

But due to the high frequency noise currents to ground ( up to 0.5mA permitted) you may experience a tingle if your laptop touches a sensitive body area like a wrist or kneecap when your feet are wet or hands earthed to plumping and you bump laptop on counter with your wrist. It can also degrade external mic noise with hum until the laptop case is grounded say thru the VGA port to a external monitor. This makes the EMI common mode noise much less for the high impedance mic but also increases risk for ground faults but unlikely in a redundant grounded stationary monitor.

I hope that makes sense....

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  • \$\begingroup\$ In Europe 2 of 3 phases....? Why only 2 and not 3 phases? \$\endgroup\$ – Uwe Sep 28 '16 at 14:37
  • \$\begingroup\$ No need for 3ph. in residential power L1-N for small appliances, L1-L2 for large to increase power at lower current (stove) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Sep 28 '16 at 14:37
  • \$\begingroup\$ @Uwe: In Europe Household connections have one phase connection and sometimes 3. The use is as follows: L1-N for small appliances. L1-L2 for large appliances like electrical stoves. L1-L2-L3 for power appliances like 3ph motors. Even if all three phases are entering the building they are not always used. \$\endgroup\$ – Decapod Sep 28 '16 at 16:50
  • \$\begingroup\$ @Tony:Please see comment to Uwe \$\endgroup\$ – Decapod Sep 28 '16 at 16:51
  • \$\begingroup\$ @Tony: In Germany we have household connections with one phase or three phases, but not two phases. We also have electrical stoves using all three phases, some are configurable to use 1 or 3 phases. \$\endgroup\$ – Uwe Sep 29 '16 at 9:08
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Neutral is defined by the socket (or not)

Each plug or socket has a design specification. That decides where neutral goes. For some socket types, it does specify at all.

Keep in mind that the very concept of neutral is not at all a given. Consider NEMA 6: no neutral, it's not in the connector.

Consider 480V "delta" (non-wild-leg), it is an isolated service which inherently has no neutral. It can be provisioned as an isolated system with no bias to ground.

Neutral Is Not Ground

Neutral and ground are bonded at the main service. That does not mean neutral and ground are the same. Neutral is the current return. Ground is a safety shield. It protects humans from shock, and equipment from lightning and ESD damage.

The Electrical Codes define neutral as a conductor, which means working current normally flows over it. Ground is not a conductor, and is not counted where conductors are considered, such as wire heating and eddy current effects. Current never travels on ground except during a fault condition.

What defines neutral is that it's near ground potential. It is not at ground potential because of voltage drop in conductors. Remember, while voltage drop in a "hot" conductor makes it drop -- voltage drop in a neutral makes it rise. It should still be within a few volts of ground.

Stick your knife anywhere you like - at your peril

If you stick your knife in the neutral pin, provided the system is healthy, you are OK unless you are also touching something at "hot" potential. However if your system has a problem, that may not be so. Electricity follows all possible paths back to source, in proportion to their conductance (inverse of resistance). If you have a damaged neutral or a broken grounding system, its conductance may be low enough that you look like a usable path. In which case you will be shocked.

The goal of neutral (and ground) is to give a much better path than you.

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http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepic/recept.gif It's supposed to be the left one if you're in the US.

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  • \$\begingroup\$ Welcome to the EE Stack and Stack Exchange! Don't be discouraged by the downvotes! Here we are always looking to promote the top quality answers. Maybe edit yours to explain a little more as to the original post (Why wouldn't you get shocked?) and add some more details! \$\endgroup\$ – user86234 Sep 28 '16 at 14:18
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    \$\begingroup\$ The USA National Electrical Code (NEC) does not require the receptacle to be mounted with the neutral pin at the bottom, although that orientation preference seems to have the majority. If it is mounted the opposite way, the neutral pin is on the right. It is best to describe the neutral as the larger of the two flat pins or use an illustration. \$\endgroup\$ – Charles Cowie Sep 28 '16 at 14:30
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The connection of neutral and live on the socket is not regulated in many if not all countries in Europe. UK is most probably an exeption. The reason is simple. The plug can be inserted either way. So it only makes sense in situation where the plug can only be inserted one way.

The voltage level of the neutral is intended to be 0V in respect to the PE (protected earth). These both lines come in most situation together on the distribution transformer. There the neutral and PE are connected to a large earth electrode.

In socalled balanced systems (three phase) the neutral did not carry a lot of current in the past. This however is changeing due to the use of led systems where the 3e harmonic of the mains frequency causes a strong current in the neutral conductor.This results in the situation that the neutral is not always at 0 V in respect to PE anymore. In new installations the main cables are thicker so the problem remains under control.

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Per French regulations, the neutral is on the left and the phase on the right.

http://www.schema-electrique.net/schema-cablage-branchement-tableau-electrique.html

However, at the wall outlet you will often find that the lines are wired "back to front" !

Pole-Volter

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Neutral is on the left for a UK BS1363 socket outlet (square pin 13A plug). This is labelled '2' in the graphic below, the blue conductor is neutral.

UK plug

In the UK, there are various different ways that the neutral can be connected to earth (in the property or on the distribution network, or at multiple locations (PME)), so it is typically only a few volts away from earth. However, it should never be considered safe to be touched until the circuit is reliably isolated.

If you want to learn more about UK earthing and neutral connections, you might find this IET publication useful.

And in answer to your later edit, the DC output from a laptop power supply should be isolated from the mains input, so shouldn't be connected to any of the pins of the mains plug. This is required for EU safety compliance, and presumably similar in most other countries. However, some supplies have poorly designed insulation which can easily fail and create a connection from mains to low voltage.

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  • \$\begingroup\$ What you indicate on the connection inside a power supply can not be correct. This would mean that there is a direct danger of electrocution. \$\endgroup\$ – Decapod Sep 28 '16 at 14:08
  • \$\begingroup\$ @Decapod can you clarify what was incorrect about my description of a typical power supply and fault conditions? I have read it over and it seems correct. \$\endgroup\$ – rolinger Sep 28 '16 at 15:40
  • \$\begingroup\$ "Some poorly designed supplies do have a connection". Even sloppy designs never have a direct connection between the mains side and the low voltage side. \$\endgroup\$ – Decapod Sep 28 '16 at 16:44
  • \$\begingroup\$ "And in answer to your later edit, the DC output from a laptop power supply should be isolated from the mains input, so shouldn't be connected to any of the pins of the mains plug." Surely this is incorrect - the output can be connected to the Ground pin of the mains plug. It should not be connected to the live or neutral pin. \$\endgroup\$ – Kevin White Nov 29 '16 at 3:23

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