Miracle: Friend Not Electrocuted Moving Cable w/ Metal

  • Context: High School 
  • Thread starter Thread starter Sakha
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Discussion Overview

The discussion revolves around an incident where a participant's friend moved a cable with a metal piece and caused a short circuit without receiving an electric shock. Participants explore the reasons behind this occurrence, touching on electrical safety, the behavior of electrical circuits, and misconceptions about voltage and current.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the resistance between the live and neutral cables during the short circuit was significantly lower than the resistance through the friend to the ground.
  • Another participant proposes that the metal likely touched the neutral wire first before shorting to the hot wire, implying that if the hot wire had been contacted first, the friend would have experienced a shock.
  • Concerns are raised about the safety practices of the friend, with one participant questioning the lack of circuit shutdown procedures and emphasizing the dangers of electric shock, particularly at 200 milli-amps.
  • There is a recounting of the friend's attitude towards the incident, where he downplays the danger of 120V, leading to a discussion about misconceptions regarding voltage and current.
  • One participant asserts that even low currents can be lethal, highlighting the dangers of hand-to-hand or hand-to-foot transmission paths through the body.
  • Another participant shares an anecdote about a friend who experienced a high voltage jolt, emphasizing that it is the current that poses the real danger, not just the voltage.
  • A later post mentions that skin resistance can vary significantly, particularly when moist, which can affect the risk of electric shock.
  • One participant shares their experience with repairing tube-operated guitar amplifiers, emphasizing the importance of safety checks after disconnecting power to avoid electric shocks from residual voltage.

Areas of Agreement / Disagreement

Participants express differing views on the safety of the situation and the understanding of electrical hazards. There is no consensus on the implications of the friend's actions or the nature of the risks involved.

Contextual Notes

Participants discuss various assumptions about electrical safety, including the effects of skin resistance and the importance of proper circuit handling. The conversation reflects a range of knowledge levels regarding electrical systems and safety protocols.

Sakha
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Today, a friend was moving a cable with a little piece of metal. He happened to cause a short circuit and nothing happened to him. The circuit was holding around 10 white lamps, 120V and I can guess its about 40W each. The little piece of metal even got perforated, and yet nothing happened to him. Thanks God.
Can anyone explain me how can this happens?
 
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The resistance between the live+neutral cables through the short was a lot less than the resistance through him to the ground
 
The neutral wire is at ground potential. The metal probably touched the neutral wire first and then shorted to the hot wire. If it had touched the hot wire first your friend would have at least received a shock.
 
Sakha said:
Today, a friend was moving a cable with a little piece of metal.

Why? This is crazy! Do you guys know how to shut the circuit off before working on it and how to verify that it is indeed off? 200 milli-amps (1/5 of one amp) is enough to be deadly. If this was a circuit in a house, it's probably a 15 amp line. Note the difference.
 
Last edited:
He broke the switch itself and was trying to put the plastic together with a little piece of metal he found, so the teacher woulnd't punish him for breaking it. Yes I forgot to say it was in school.
After that I told him "You know that could've killed you", and as many people say, he replied "Nah, 120V won't kill me".
 
Sakha said:
He broke the switch itself and was trying to put the plastic together with a little piece of metal he found, so the teacher woulnd't punish him for breaking it. Yes I forgot to say it was in school.
After that I told him "You know that could've killed you", and as many people say, he replied "Nah, 120V won't kill me".

You might ask the teacher to discuss that in class.
 
Sakha said:
After that I told him "You know that could've killed you", and as many people say, he replied "Nah, 120V won't kill me".
Your friend is badly misinformed. Hand-to-hand or hand-to-foot transmission paths through the core of your body can kill you with very little current.
 
Sakha said:
After that I told him "You know that could've killed you", and as many people say, he replied "Nah, 120V won't kill me".

Many people think that it is the voltage that kills you, which is a large misconception. In fact, I have a friend who had to receive a 5000 V jolt to pass one of his biomedical technology courses. It's the amps that are dangerous, and it doesn't take much to do the job. Human skin resistance is typically about 1 mega-ohm (10^6) for dry skin, but for moist skin the resistance can be reduced by a factor of 100.
 
  • #10
I have restored and repaired and rebuilt a lot of tube-operated guitar amplifiers. The very first thing I do with every amp after disconnecting the power and removing the chassis is to connect the B+ rail to ground and do some voltage checks to make sure that there are not some capacitors lurking to bite you.
 

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