The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

can i get electrocuted by holding the NEUTRAL ?

a circuit only needs two wires to be complete.

so how does the third wire - ground - fit in the circuit ?

"blackboab" wrote in message
oups.com...
The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second

yes

so that they swap over the roles of
positive and negative.

no

can i get electrocuted by holding the NEUTRAL ?


not if all is working properly (ie not wiring faults etc)

a circuit only needs two wires to be complete.

so how does the third wire - ground - fit in the circuit ?

it prevents dangerous voltages that might exist on metal parts of appliances
during fault conditions by connecting them to earth


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

Bob

AC current changes direction 50 times a second so the current must
first flow one way - live to neutral - and then the other way - neutral
to live.

no ?

"blackboab" wrote in message
ups.com...
Bob

AC current changes direction 50 times a second so the current must
first flow one way - live to neutral - and then the other way - neutral
to live.

It changes direction because the live varies first positve with respect to
neutral and then negative with respect to neutral. The neutral wire is
(roughly) at earth potential and stays there (more or less - in practice
under no fault conditions, there may be a few tens of volts (ac) or so on
the neutral depending on the generating and distribution arrangements.

It's the size of the voltage with resepct to earth, not its sign that causes
the toucher problems.

I did say the neutral wont electrocute you under no fault conditions. It is
true, as another poster pointed out, that, if the neutral retrun becomes
disconnected in a circuit somewhere neutrals between there and an appliance
will rise to 240V if the appliance is on, giving, clearly, the risk of
electric shock - this is a fault condition though.

As a practical example, our incoming mains supply comes overhead in a
concentric cable. The centre inner core is the live. The outer sheath is the
neutral. They are insulated from each other (obviously) and insulated
overall, to guard against a) the outer becoming live under fault conditions
b) unwanted neutral leakage currents to earth (which can be quite high where
the impedance is very low and c) corrosion of the netral sheath. When my
meter was moved, they reconnected live. The outer insulation and neutral
sheath were removed/unwound and pulled back with no protective gear. The
inner was then cut with a pair of extremely insulated cutters!

I have held neutrals many times under no fault conditions.


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

On Wed, 5 Oct 2005 08:53:23 UTC, "blackboab"
wrote:

AC current changes direction 50 times a second

No, it doesn't.

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
Avenue Supplies, http://avenuesupplies.co.uk

Bob Eager wrote:
On Wed, 5 Oct 2005 08:53:23 UTC, "blackboab"
wrote:


AC current changes direction 50 times a second


No, it doesn't.


I thought it did actually as Electrons flow from -ve to +ve IIRC, or the
current flows from +ve to -ve in conventional notation.

The live is always energised though with either a +ve or -ve potential
wrt the neutral.

Alex.

"AlexW" wrote in message
...
Bob Eager wrote:
On Wed, 5 Oct 2005 08:53:23 UTC, "blackboab" wrote:


AC current changes direction 50 times a second


No, it doesn't.


I thought it did actually as Electrons flow from -ve to +ve IIRC, or the
current flows from +ve to -ve in conventional notation.

The live is always energised though with either a +ve or -ve potential wrt
the neutral.

You fell into his little trap! It changes direction 100 times per second,
having a burst in both directions 50 times a second.


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

In article ,
says...
Bob Eager wrote:
On Wed, 5 Oct 2005 08:53:23 UTC, "blackboab"
wrote:


AC current changes direction 50 times a second


No, it doesn't.


I thought it did actually as Electrons flow from -ve to +ve IIRC, or the
current flows from +ve to -ve in conventional notation.

It changes direction twice on each cycle.

AlexW wrote:

I thought it did actually as Electrons flow from -ve to +ve IIRC, or the
current flows from +ve to -ve in conventional notation.

The live is always energised though with either a +ve or -ve potential
wrt the neutral.

Alex.

That's an approximation.

If the frequency is high enough, and/or the distance is long enough, a
lot of the power gets carried as an electromagentic wave around the
conductor.

I'm used to seeing this at MHz and GHz ranges in short conductors, but
I'm pretty sure this is why HT pylons have 4 wires with airgaps for each
conductor.

Andy

if the nutral is carrying a current at the time of you holding it then yes
you can be electrocuted......nutral is the preferd method for a current to
make it's return. ground or earth is a protection circuit and back at the
generation site is connected to nutral.

"blackboab" wrote in message
oups.com...
The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

can i get electrocuted by holding the NEUTRAL ?

a circuit only needs two wires to be complete.

so how does the third wire - ground - fit in the circuit ?

On Wed, 5 Oct 2005 08:39:23 +0000 (UTC), "pat"
wrote:

| if the nutral is carrying a current at the time of you holding it then yes
| you can be electrocuted......nutral is the preferd method for a current to
| make it's return. ground or earth is a protection circuit and back at the
| generation site is connected to nutral.

Assuming proper wiring, there will only be a *small* voltage on the neutral
wire, whatever current is being carried. IIRC it needs more than 30 volts
to kill someone, I have personally touched 30 volt supplies more times than
I care to remember without ill effects, apart from a tingle. Mind you it
is a practice best avoided ;-)

--
Dave Fawthrop dave hyphenologist co uk
The London suicide bombers killed innocent commuters.
Animal rights terrorists and activists kill innocent patients.

On 5 Oct 2005 01:21:04 -0700, "blackboab" wrote:

The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

er..sort of.

can i get electrocuted by holding the NEUTRAL ?

Yes. See above.


a circuit only needs two wires to be complete.

?


so how does the third wire - ground - fit in the circuit ?

Electricity is generated three-phase:
http://en.wikipedia.org/wiki/Three_phase
(for various reasons including efficiency)

and then for domestic supply you get one of the three live conductors,
and the neutral:
http://en.wikipedia.org/wiki/Single-...electric_power

The ground connector is for safety only - it's carried round the house
and connected to various bits of exposed metal, including those that
are part of your electrical equipment. If then you have a fault in
some device where live becomes connected to these same bits of
exposed metal, a large current briefly flows to ground and your
fuse/MCB/whatever pops, cutting off the circuit.

C

"Charlie" wrote in message
...
On 5 Oct 2005 01:21:04 -0700, "blackboab" wrote:

The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

er..sort of.

can i get electrocuted by holding the NEUTRAL ?

Yes. See above.


a circuit only needs two wires to be complete.

?


so how does the third wire - ground - fit in the circuit ?

Electricity is generated three-phase:
http://en.wikipedia.org/wiki/Three_phase
(for various reasons including efficiency)

and then for domestic supply you get one of the three live conductors,
and the neutral:
http://en.wikipedia.org/wiki/Single-...electric_power

The ground connector is for safety only - it's carried round the house
and connected to various bits of exposed metal, including those that
are part of your electrical equipment. If then you have a fault in
some device where live becomes connected to these same bits of
exposed metal, a large current briefly flows to ground and your
fuse/MCB/whatever pops, cutting off the circuit.

C

If you disconnect the neutral of a circuit at any point then the neutral
will be at 230v with respect to earth as there is no volt drop across the
load. It could then kill you.

On Wed, 5 Oct 2005 10:21:28 +0100, "Bob Watkinson"
wrote:


If you disconnect the neutral of a circuit at any point then the neutral
will be at 230v with respect to earth as there is no volt drop across the
load. It could then kill you.

indeed. If the circuit is all perfect though then the neutral *should*
be at the same potential as ground, so no current should flow. However
since the neutral is definitely a current carrying conductor you
shouldn't ever touch it in the first place, just in case.

C

Charlie wrote:
On 5 Oct 2005 01:21:04 -0700, "blackboab" wrote:


The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.


er..sort of.

can i get electrocuted by holding the NEUTRAL ?


Yes. See above.


a circuit only needs two wires to be complete.


?


so how does the third wire - ground - fit in the circuit ?


Electricity is generated three-phase:
http://en.wikipedia.org/wiki/Three_phase
(for various reasons including efficiency)

and then for domestic supply you get one of the three live conductors,
and the neutral:
http://en.wikipedia.org/wiki/Single-...electric_power

The ground connector is for safety only - it's carried round the house
and connected to various bits of exposed metal, including those that
are part of your electrical equipment. If then you have a fault in
some device where live becomes connected to these same bits of
exposed metal, a large current briefly flows to ground and your
fuse/MCB/whatever pops, cutting off the circuit.

C

Arggh, whenever people post wikipedia links I always waste hours
clicking on hyperlinks and end up learning bizarre things.

On that topic, I have a theory that in order to create the ultimate AI
computer, all that is needed it to write a program that allows the
machine to cross reference unknown words in text files. Then simply
feed the entire contents of the OED into it and let it site there for a
bit while it cross references every word in it. It will then be able to
reccursively cross-reference every word and gain total and utter
comprehension of the English language.

In article , Richard Conway
wrote:
On that topic, I have a theory that in order to create the ultimate AI
computer, all that is needed it to write a program that allows the machine
to cross reference unknown words in text files. Then simply feed the
entire contents of the OED into it and let it site there for a bit while
it cross references every word in it. It will then be able to
reccursively cross-reference every word and gain total and utter
comprehension of the English language.

30 years ago that's what we thought. Then computers started to get fast enough
to do a very small amount of that task and we realised that each word didn't
need simple hooks to other words but a whole word-specific program of their
own. AI (true AI) is now further away than it was in the late seventies. ;-(

I don't know how she worked it out - or how much it was deliberate - but my 14
month old granddaughter calls our small dogs 'dog' and her own (much larger)
dog 'dog-dog'. One of us swears that, on seeing a horse, she called it
'dog-dog-dog'. Now tell me how you'd program a computer to produce the
possible grammar behind that!

--
John Cartmell john@ followed by finnybank.com 0845 006 8822
Qercus magazine FAX +44 (0)8700-519-527 www.finnybank.com
Qercus - the best guide to RISC OS computing

John Cartmell wrote:
In article , Richard Conway
wrote:

On that topic, I have a theory that in order to create the ultimate AI
computer, all that is needed it to write a program that allows the machine
to cross reference unknown words in text files. Then simply feed the
entire contents of the OED into it and let it site there for a bit while
it cross references every word in it. It will then be able to
reccursively cross-reference every word and gain total and utter
comprehension of the English language.


30 years ago that's what we thought. Then computers started to get fast enough
to do a very small amount of that task and we realised that each word didn't
need simple hooks to other words but a whole word-specific program of their
own. AI (true AI) is now further away than it was in the late seventies. ;-(

I suppose the problem is that even if it could cross reference all the
words, it still wouldn't actually know what any of them mean.

I don't know how she worked it out - or how much it was deliberate - but my 14
month old granddaughter calls our small dogs 'dog' and her own (much larger)
dog 'dog-dog'. One of us swears that, on seeing a horse, she called it
'dog-dog-dog'. Now tell me how you'd program a computer to produce the
possible grammar behind that!

You'd have to create an algorithm that took factors such as the
dimensions and mass of an animal and output the word dog x number of
times as a result!

In article , Richard Conway
wrote:
I don't know how she worked it out - or how much it was deliberate - but
my 14 month old granddaughter calls our small dogs 'dog' and her own
(much larger) dog 'dog-dog'. One of us swears that, on seeing a horse,
she called it 'dog-dog-dog'. Now tell me how you'd program a computer to
produce the possible grammar behind that!

You'd have to create an algorithm that took factors such as the dimensions
and mass of an animal and output the word dog x number of times as a
result!

That's easy enough. The problem is how the easily-communicated idea developed
in the first place. No one has taught her the concept of multiple words =
bigger and, at the stage of hardly even having a communicable vocabulary
(whilst she talks plenty I don't pretend to understand any of it - except to
her!) she appears to have generated a grammar of her own. This isn't a new
observation: very young children brought up in a family using (deaf) sign
language will probably acquire a formal, slow, limited, grammar but - where
able to converse with other, similar kids at a young enough age, develop a
natural fast, open-ended grammar of their own making.
this is uk.d-i-y.grammar isnt it?
Organic life is far more proficient than any artificial equivalent that we can
(yet) design.

--
John Cartmell john@ followed by finnybank.com 0845 006 8822
Qercus magazine FAX +44 (0)8700-519-527 www.finnybank.com
Qercus - the best guide to RISC OS computing

"blackboab" wrote in message
oups.com...
The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

AC is usually regarded as not having positive and negative.


can i get electrocuted by holding the NEUTRAL ?

You can get electrocuted by holding any of the wires in a mains installation
(even if its only a fault that does it).
Treat all wires as though they could be live and you will survive for
longer.


a circuit only needs two wires to be complete.

Not strictly true as some circuits don't need wire to complete.


so how does the third wire - ground - fit in the circuit ?


Its the *most important* wire.
Its there to stop some common faults killing you.

"blackboab" wrote in message
oups.com...
The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

Yep

can i get electrocuted by holding the NEUTRAL ?

You shouldnt do, becasue back at the electrcity sub station the nuteral is
connected to the earth (and in the brown stuff outside) so everything is
connected to nutral all the time.

a circuit only needs two wires to be complete.

so how does the third wire - ground - fit in the circuit ?

The ground, or earth wire is only there for protection, if there was a fault
in an appliance where the live or the neutral wire somehow came into contact
with the metal casing of something, the current will travel down this wire
instead of down the neutral wire.
Now, if the wire that has become connected to the metal casing of the
appliance is the Live, this is effectively shorting the live to the neutral,
causing a lot of current to flow (because neutral is connected to the earth)
so your fuse or little MCB (Circuit breaker) will blow/trip.

Also, if you have an RCD, this checks the current going out of the Live, and
returning back via the Neutral, if there is an imbalance (because some is
going to earth, maybe through a person, or the earth wire etc.) then the RCD
trips.

Sparks...

Sparks

if the live wire comes loose and touches the metal case
of my toaster then the current flows from the generator down the live
wire , through the metal case, through the earth wire to ground,
through the ground back to the generator where it goes up the earth
wire there to neutral ?

when the neutral wire touches the metal case is the circuit simply
totally grounded with the neutral wire at the same potential as the
ground to which its connected ?

"blackboab" wrote in message
oups.com...
Sparks

if the live wire comes loose and touches the metal case
of my toaster then the current flows from the generator down the live
wire , through the metal case, through the earth wire to ground,
through the ground back to the generator where it goes up the earth
wire there to neutral ?

That's right - but as there isnt much resistance in this circuit, lots and
lots of current flows (as it is effectivly a short circuit) so the fuse or
circuit breaker will brlow/trip

when the neutral wire touches the metal case is the circuit simply
totally grounded with the neutral wire at the same potential as the
ground to which its connected ?

yes - if you dont have an RCD, then this fault will remain undetected, but
as long as the earth is all connected properly, then the toaster will still
finction and you shouldnt get a shock.

If you did not have an RCD, and you connected somthing to Live and Earth,
the appliace should work and nothing should blow or trip

If the circuit has an RCD, then some of the current will return via the
nutral wire, but some will return through the earth. The RCD will see that
there is an inbalance between the current flowing from the live and
returning via the nutral (It doesnt care where it has gone, it just knows it
is missing!), and it will trip.
Sockets will usually have a 30mA RCD - this will trip if the inbalanace is
30mA or greater.

This means, if there was a fault with your toaster where either the live or
the neutral was in contact with the metal casing, but the earth wire was not
connected, if you touch the metal casing, some current will be conducted
through you to earth - the RCD will spot this missing current, and trip,
hopefully saving your life :-)

Sparks...

This means, if there was a fault with your toaster where either the live
or
the neutral was in contact with the metal casing, but the earth wire was
not
connected, if you touch the metal casing, some current will be conducted
through you to earth - the RCD will spot this missing current, and trip,
hopefully saving your life :-)

Sparks...

Just curious. How safe is an RCD. If I stood bare footed on a damp concrete
floor and grabbed the Live wire, would it still be a nasty shock but not
kill me, or does it switch off so quick that I would not even notice it.

Simon

"Simon" wrote in message
...

This means, if there was a fault with your toaster where either the live
or
the neutral was in contact with the metal casing, but the earth wire was
not
connected, if you touch the metal casing, some current will be conducted
through you to earth - the RCD will spot this missing current, and trip,
hopefully saving your life :-)

Sparks...

Just curious. How safe is an RCD. If I stood bare footed on a damp
concrete
floor and grabbed the Live wire, would it still be a nasty shock but not
kill me, or does it switch off so quick that I would not even notice it.

Simon

Assuming the RCD is working correctly it would trip between 10 and 20
milliseconds while carrying 30mA (depending on type). To quick for you to
feel it I would think but as they say 'Don't try this at home folks'.

"Simon" wrote in message
...

This means, if there was a fault with your toaster where either the live
or
the neutral was in contact with the metal casing, but the earth wire was
not
connected, if you touch the metal casing, some current will be conducted
through you to earth - the RCD will spot this missing current, and trip,
hopefully saving your life :-)

Sparks...

Just curious. How safe is an RCD. If I stood bare footed on a damp
concrete
floor and grabbed the Live wire, would it still be a nasty shock but not
kill me, or does it switch off so quick that I would not even notice it.

It depends on your heart really, if you were in good health, then I expect
you would be OK, but dont try it!! You would feel it for sure.
The RCD should trip extremly fast (I think it has to be at most .04 of a
second)

Sparks...

On 5 Oct 2005 01:21:04 -0700, "blackboab"
scrawled:

The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

No, it's live and neutral you're after. Positive and negative are for
DC. I'd forget about the swapping over bit, it sort of isn't relevant.

can i get electrocuted by holding the NEUTRAL ?

Yes

a circuit only needs two wires to be complete.

Technically.

so how does the third wire - ground - fit in the circuit ?

There for protection, as others have explained.
--
Stuart @ SJW Electrical

Please Reply to group

I dont want to be pedantic but AC current is just swapping the positive
and negative electrodes around 50 or 100 times a second,

so positive and negative are switched around by AC current,

http://www.tpub.com/neets/book2/1.htm

AC AND DC

Alternating current is current which constantly changes in amplitude,
and which reverses direction at regular intervals. You learned
previously that direct current flows only in one direction, and that
the amplitude of current is determined by the number of electrons
flowing past a point in a circuit in one second. If, for example, a
coulomb of electrons moves past a point in a wire in one second and all
of the electrons are moving in the same direction, the amplitude of
direct current in the wire is one ampere. Similarly, if half a coulomb
of electrons moves in one direction past a point in the wire in half a
second, then reverses direction and moves past the same point in the
opposite direction during the next half-second, a total of one coulomb
of electrons passes the point in one second. The amplitude of the
alternating current is one ampere. The preceding comparison of dc and
ac as illustrated. Notice that one white arrow plus one striped arrow
comprise one coulomb.

blackboab wrote:
The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

can i get electrocuted by holding the NEUTRAL ?

a circuit only needs two wires to be complete.

so how does the third wire - ground - fit in the circuit ?

See http://amasci.com/amateur/whygnd.html

MBQ

great article. the current goes from live to neutral and back again 50
times a second as explained here

@@@@@@@@@@@@@@@@@@@@@@'

But still, every once in a while a Customer will get a really nasty
shock
from a cheap plastic appliance that's wet. Or perhaps an electric hair
dryer will fall into the bathtub, but the short-circuit current in the
water won't be enough to blow the fuses in the house, and the bathtub
water will become lethal. In theory there is a way to prevent this.
These Customer shocks are happening because the customers' bodies offer
a
path for current between the appliance and the lightning-safety earth
grounds. During the shocking event, some of the flowing charge is
going
in (and out) of the "hot" wire, but it is NOT going back into (and out
of)
the "neutral" wire as it's supposed to. Instead, it's going through
the
human, and also going into the grounded pipes of the plumbing.

If we could measure the current that's taking the "wrong" path, maybe
we
could detect the problem and turn off the power before anyone dies. We
can't measure the current in the plumbing, but we can measure it in the
"hot" wire, measure the current in the "neutral" wire, then subtract
them. This tells us what level of current was escaping via the
"illegal"
path through the human to ground. The subtraction should normally give
a
zero result, since there never should be a current path to ground that
isn't using the neutral wire. If we amplify the subtraction's result
and
use it to trip a circuit breaker, we'll have a new type of appliance
which
turns itself off immediately when a human gets into the electrical
path.
These devices are now required in wet areas of homes (bathrooms.)
They're
called Ground Fault Interrupters. And so we've finally entered modern
times, the "Age of the Electric Outlet with the Little Red Button Which
Pops Out!"

On 5 Oct 2005 09:16:56 -0700, "blackboab"
scrawled:

These devices are now required in wet areas of homes (bathrooms.)
They're
called Ground Fault Interrupters. And so we've finally entered modern
times, the "Age of the Electric Outlet with the Little Red Button Which
Pops Out!"

Er, this is uk.d-i-y, note the UK bit.
--
Stuart @ SJW Electrical

Please Reply to group

i know.

but most of the information is still relevant.

say what you want about the yanks being imperialist , war-mongering
*******s but their technical knowledge is pretty impressive, at least
they make good websites,

blackboab wrote:

but most of the information is still relevant.

Apart from the bit about having sockets allowed in bathrooms...

say what you want about the yanks being imperialist , war-mongering
*******s but their technical knowledge is pretty impressive, at least
they make good websites,

Alas their electrical installations are of state of the ark in
comparison to ours. So of very limited use as a source of reference
material.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article .com,
blackboab wrote:
The LIVE and NEUTRAL wires are both passing current and the current is
reversing at 50 times a second so that they swap over the roles of
positive and negative.

It's actually 100 times a second. The 50 Hz refers to a full cycle - from
zero to + then zero to - and back to zero. Relative to *both* conductors.

can i get electrocuted by holding the NEUTRAL ?

What causes harm is potential difference. You could have a million volt
supply, and if one side is earthed you should be able to touch that
conductor safely. But not the other one...;-)

a circuit only needs two wires to be complete.

so how does the third wire - ground - fit in the circuit ?

In an ideal world both neutral and earth are at the same potential.

--
*A fool and his money can throw one hell of a party.

Dave Plowman London SW
To e-mail, change noise into sound.