ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

Topic Options
Rate This Topic
#129071 - 07/10/04 05:48 AM why we do not fell shock in neutral?
luckyali Offline
Junior Member
Registered: 06/22/04
Posts: 7
Loc: pakistan
In single phase current flow through phase and returned to neutral.when we touch the phase we fell shock but when touch the neutral we don`t,while current is also present in neutral.if we take the example of pipe and water,the water is present at every point of pipe,so please tell me why we do not fell shock in neutral?
Top
Tools for Electricians:
#129072 - 07/10/04 09:18 AM Re: why we do not fell shock in neutral?
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
Hi Ali,

The reason is that in a system which is functioning normally the neutral has no, or very little potential with respect to earth.

On a normal supply the neutral side of the transformer is grounded. So the "hot" side of the line is at 120, 240, or some other voltage with respect to the earth. If you touch it while simultaneously in contact with the earth, you therefore have that voltage applied across your body and you feel a shock.

But even though current is flowing through the neutral, the only voltage present on it is a very small amount due to voltage drop along the cable. So you may have just 1 or 2 volts on it with respect to earth -- Not enough to shock you.
Top
#129073 - 07/10/04 10:05 AM Re: why we do not fell shock in neutral?
ElectricAL Offline
Member
Registered: 10/10/01
Posts: 597
Loc: Minneapolis, MN USA
Ali,

Following on Paul's last two sentences, look at this situation:
When the tool is working normally, the current flowing will be about 7 Amps. The circuit and its resistance can be shown by this diagram:
When the circuit works normally and 7 Amps is flowing, the touch voltage on the neutral will be:

(R4 + R6)* 7 Amps = 2.1 Volts. Too low to feel.

(R1 and R2 are so big, compared to R4 and R6, that they can be ignored to simplify the calculation; and R7 and R8 aren't present, cause the tool is working normally, that is, the hot wire hasn't broken loose and touched the grounded metal of the tool body.)

When the hot wire shorts to the tool body, and is not connected to the neutral, the current that flows is 188 Amps and all of a sudden, the person not only gets shocked, but because of the bad conditions (weather, mud, sweat) gets badly shocked. The circuit becomes this equivalent:
_________________________
Al Hildenbrand
Top
#129074 - 07/10/04 07:30 PM Re: why we do not fell shock in neutral?
luckyali Offline
Junior Member
Registered: 06/22/04
Posts: 7
Loc: pakistan
Thx very much both of U Paul and electrical.
Top

Member Spotlight
Member Since: 10/07/00
Posts: 3417
New in the Gallery:
SE cable question
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box


Who's Online
0 registered (), 54 Guests and 7 Spiders online.
Key: Admin, Global Mod, Mod
 
New in the Gallery:
SE cable question
 
Top Posters (30 Days)
Admin 51
HotLine1 43
gfretwell 17
Trumpy 16
Ruben Rocha 13
 
Newest Members
clee512, Jdscott2005, FAIZAN, Regitest2, sureshazhagai

ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals