Neutral wire-isnt it active always ??? !!!

[rahulr88]

why don we get a shock on touching the neutral wire...???
in the main switch board of my house,using a tester, i tested the neutral wire...and i found that it s not glowing...i couldn find a reason for that...since the supply is alternating,it should show that neutral s also active...but i couldn see anything...please answer my question ...

 

[flatulent]

The neutral wire in a three phase power system and also in a one phase 220-110 V system is connected to the earth at the transformer output.

This is independent of the safety wire connected to earth at the building power entrance.

 

[barrybear]

The neutral wire will be connected to earth at many points between you and supply generator

 

[kender]

The load induces current through the neutral, as a result there's a voltage difference across the neutral. This voltage can be as high as 20V w.r.t. earth ground (with respect to) depending on the load an the resistance of the neutral. This voltage is the source of the shock.

 

[rahulr88]

first of all i thank u all for ur answers...but i still have doubt...if the neutral wire is earthed at different places,it will be having ground potential(zero pot.)...then only phase ll be active... that means just 110V...then how do the appliances work...
:?:

 

[kender]

first of all i thank u all for ur answers...but i still have doubt...if the neutral wire is earthed at different places,it will be having ground potential(zero pot.)...then only phase ll be active... that means just 110V...then how do the appliances work...
:?:

The short answer is: No, the appliance end of the neutral will not be at ground potential, when the appliance is pulling current, because the neutral wire has resistance (it's not an ideal conductor).

Why do you think that the appliance will not work?

 

[rahulr88]

i thought when neutral wire is earthed , it ll be at ground potential(0 volts)...so only 110 volt drop will be there acoss the appliance...then how does it work ???
if it is designed for 220 volts...my dear frnd...how the circuit diagram would be in such a case ??? if the neutral is earthed,it ll be at ground pot.and u r saying it won't be ...i am not understanding !!!
my question may be a big blunder...please excuse me ...i am a beginner...

 

[jallem]

The neutral sometimes is not provided as in
delta system. So neutral is taken of ground
bar directly. This creates stray currents. That
is for old systems. New system provide neutral
and theoretical would be same potential than
ground but due to distances and corrosion among
others causes, there will be a "small" difference
between neutral and ground, specially if ground
is not perfect due to short bar grounding or
dry soil, etc. Other cause would be an unbalance
on the three phase system, which cause that the
neutral get some potential above ground.

 

[johnyaya]

My turn. Lets see if I can shed some light.
Picture this: You have a single-phase transformer, primary side is 220V, secondary side is 110V. The secondary side of the transformer has 2 wires. We'll call them "hot" and "neutral". The load goes across the 2 wires of the secondary. Now, pick one of the secondary wires at the transformer and also attach it to earth ground (we'll use the one we're calling "neutral"). The secondary voltage is still the same, the load still sees the secondary voltage. It's just that now you have a point of reference, earth ground. If you look in your main power panel you will see that earth ground and the neutral bus are connected there. On sub-panels located further than 40 ft. away, electricians are required to connect another ground rod to the neutral bus again. The main feed into your house usually has two-phases (L1 and L2), but the idea is still the same.

Now for your tester light. The tester light requires a minimum voltage before it will light, so just about anywhere along the neutral wire you will not have enough voltage (relative to earth ground) to light the lamp.

The same current is flowing through both the hot and neutral wires. A GFI outlet or GFI circuit breaker is used to detect any current going directly to ground instead of back through the neutral (ie. you're getting shocked), and breaks the circuit. But this is a different subject.

Is it any clearer now?