Line Wire

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LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Student, welcome to the forum! :)

Rule #1: Touching live wires intentionally is not smart.

What you feel as a shock is from the current, which is driven by the potential difference (voltage) between two points. The current is limited by the resistance between the two contact points of your body.

Please remember Rule #1. ;)
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Severity of shock is due to contact resistance. I missed that one on a test, I answered amperage.
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
When we touch the line wire or supply wire we get shock. What is that? Is it voltage or current or something else?

Shocks and Burns are caused by current flowing through the body and not due to the voltage. However current flowing through the body follows ohm's Law I =V/R.

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broadgage

Senior Member
Location
London, England
To receive a shock, one must touch a wire or other conductor, at the same time as being in contact with the ground/a grounded article, or whilst being in contact with another conductor energised at a different voltage.

Most electric shocks are between energised conductors and ground.
A minority are whilst insulated from ground, the shock resulting from touching two energised conductors at different voltages.

It is in theory perefctly safe to touch an energised conductor, if completly insulated from ground. Please dont try it though as a mistake could kill.

Every year people die as a result of touching energised overhead lines, yet birds perch upon these without harm. The bird is well away from ground, but the person is likely standing on the ground, or is in contact with grounded articles.

The degree of danger is in rough proportion to the current that passes through the body NOT to the normal operating current* of the circuit touched.
Touching a 120 volt conductor carrying 1,000 amps is no more dangerous than one carrying 15 amps, as regards electric shock.

Other factors being equal, high voltage circuits are more dangerous becuase the higher voltage, under similar conditions, will result in a greater current through the body.

*High current circuits are more dangerous as regards arc flash and burns, but not as regards electric shocks.
 

topgone

Senior Member
To receive a shock, one must touch a wire or other conductor, at the same time as being in contact with the ground/a grounded article, or whilst being in contact with another conductor energised at a different voltage.

Most electric shocks are between energised conductors and ground.
A minority are whilst insulated from ground, the shock resulting from touching two energised conductors at different voltages.

It is in theory perefctly safe to touch an energised conductor, if completly insulated from ground. Please dont try it though as a mistake could kill.

Every year people die as a result of touching energised overhead lines, yet birds perch upon these without harm. The bird is well away from ground, but the person is likely standing on the ground, or is in contact with grounded articles.

The degree of danger is in rough proportion to the current that passes through the body NOT to the normal operating current* of the circuit touched.
Touching a 120 volt conductor carrying 1,000 amps is no more dangerous than one carrying 15 amps, as regards electric shock.

Other factors being equal, high voltage circuits are more dangerous becuase the higher voltage, under similar conditions, will result in a greater current through the body.

*High current circuits are more dangerous as regards arc flash and burns, but not as regards electric shocks.

At higher voltage, just being near the HV lines - too close than what is safe can get you shocked!
 

brian john

Senior Member
Location
Leesburg, VA
At higher voltage, just being near the HV lines - too close than what is safe can get you shocked!

If the clothing you are wearing (shoes in particular) allow you to be at a different potential, Or if noted if you are touching a surface at a different potential.

BUT as noted touching energized conductors or standing too close IS NOT SOMETHING that should be done.
 

glene77is

Senior Member
Location
Memphis, TN
At higher voltage, just being near the HV lines - too close than what is safe can get you shocked!

Top,

That sounds like a capacitive coupling,
wherein no contact is required, but it makes your hair stand on end.
I have worked around high voltage RF circuits,
and received arcing burns at 1/2 inch distance.

Blue Collar Electricians don't normally have to deal with extreme voltage,
nor R.F. high frequency circuits. Lucky!

Your words of caution are good advice. :)
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Severity of shock is due to contact resistance. I missed that one on a test, I answered amperage.


Depending on exactly how the question is worded, I'd say you got that question right, and the person who wrote the test needs to think about the question and answer a little more.

I could have the same contact resistance when I touch 10 volts as when I touch 100 volts, but the shock won't be the same severity.

So contact resistance isn't a sole determining factor on how severe a shock is, but amperage (through the person) is a sole determining factor.
 

zog

Senior Member
Location
Charlotte, NC
Duration is a bigger factor than the amount of current, but they both come into play. There are many factors that determine the severity of an electrical shock and they are explained in detail in IEEE Std 80 and IEC 479-1.
 

glene77is

Senior Member
Location
Memphis, TN
Does it not become an open circuit?

Ham,
What is the Impedance of the human body (ball park figure for discussion) ?
You are referring to a resistive scenario: I=E/R

ZOG quote: So you rub your socked feet on the carpet in the winter and touch the doorknob, the several thousand volt charge passes how much current through your body? Not what Ohms "law" would tell you it is.
endquote:

Zog is referring to a dynamic scenario, with reactive factors.
Human-body impedance with high static charge (DC) and a contact point (touch the door-knob) and the impedance of the door-knob to reference ground.
Power available for the static discharge should remain fixed.
Voltage discharged will preceed the current flow,
based on the reactive factors of the discharge circuit (which includes the door-knob and the human-body).

It does not look like a clear Ohm's Law scenario.
I would like to hear your comments. :)
 
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