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How much electricity is dangerous? Answered

I found plans to make a device to give yourself a static charge using a negative ion generator. It outputs 7.5 kV and 10 mA. I've seen it in use and I know it's not dangerous. I wanted to build two of them together making it output 15 kV. Unfortunately that would also make it 20 mA. I'm not sure what the resistance of the human body is so I guess my question is will 15 kV and 20 mA flowing through a person be dangerous? Thank you for the replies and I'm sorry if this is a stupid question. I'm pretty new to my electronic hobbies.

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blkhawk (author)2012-06-29

Anything above 30 volts is considered lethal. That is enough to cause fibrillation and death.

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steveastrouk (author)blkhawk2012-06-30

No volts don't kill, current kills.

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blkhawk (author)steveastrouk2012-06-30

"In industry, 30 volts is generally considered to be a conservative threshold value for dangerous voltage. The cautious person should regard any voltage above 30 volts as threatening, not relying on normal body resistance for protection against shock"

I used as reference Lessons in Electric Circuit.

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steveastrouk (author)blkhawk2012-07-01

I am perfectly aware of that, however my point is thateven 30 volts CAN, in admittedly bizarre circumstances, kill.

The key parameter is current through the heart. It is well established that 20ma through the heart of EVEN a healthy individual can induce ventricular fibrillation.MUCH LESS can kill a child our sick adult. don't rely on 30v as soon magic level.

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blkhawk (author)steveastrouk2012-07-01
Using the same reference:

A common phrase heard in reference to electrical safety goes something like this: "It's not voltage that kills, its current!" While there is an element of truth to this, there's more to understand about shock hazard than this simple adage. If voltage presented no danger, no one would ever print and display signs saying: DANGER -- HIGH VOLTAGE!

The principle that "current kills" is essentially correct. It is electric current that burns tissue, freezes muscles, and fibrillates hearts. However, electric current doesn't just occur on its own: there must be voltage available to motivate electrons to flow through a victim. A person's body also presents resistance to current, which must be taken into account.

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steveastrouk (author)blkhawk2012-07-01

So where's the argument ? Do you REALLY think that I need to be told that ?

Yes, without volts there is no current, but with a low enough resistance, that voltage can drive enough current to kill. 1.5Volts, delivered in the right, low resistance condition, would kill. How does that fit with your trite "Anything above 30 volts is considered lethal." ?

30 V is not, from the the IEC's point of view, considered lethal.

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blkhawk (author)steveastrouk2012-07-01

I find a contradiction when you say first that: " however my point is that even 30 volts CAN, in admittedly bizarre circumstances, kill." and then you say: "30 V is not, from the the IEC's point of view, considered lethal." Which is it?

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steveastrouk (author)blkhawk2012-07-02

As I clearly said, "under bizarre circumstances", I am at a loss to see where the contradiction lies ?

If I were to place thick needles through your skin, around your heart, and apply 1.5V, I could stop your heart, or at least break its rhythm. This is unlikely, and bizarre.

Clearer ?

Under those circumstances 1.5 V would be "lethal".

In actual fact, voltages below 50V (IEC) are considered "safe, extra low" - after all, telephone circuits work with 50V signals.

More than that, and, with less unlikely circumstances, and a low enough impedance, it becomes possible for the voltage to cause a lethal current to flow through the heart.

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blkhawk (author)steveastrouk2012-07-02

Would you please cite where it says that 50 V are "safe"? Would you please cite what is the safest voltage someone can work with? What is the industry standard in regards to electric safety? I don't think that there is much difference between British and American standards.

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steveastrouk (author)blkhawk2012-07-02

IEE regs, 16th edition, Chapter 7, define several kinds of "extra low voltage", voltages not exceeding 50 V AC, 120V DC.

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steveastrouk (author)blkhawk2012-07-01

I note that the author has no professional qualifications. Be careful where you put your faith.

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blkhawk (author)steveastrouk2012-07-01

Anthony R. Kuphaldt is an instructor of Instrumentation and Control Technology, Bellingham Technical College. His web page is hosted by the University of North Carolina.

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steveastrouk (author)blkhawk2012-07-02

Cite. I couldn't see any sign of his qualifications in a single page Google search. It may be a difference in nomenclature, but here, an instructor is not a lecturer, and wouldn't necessarily have to have a professional qualification, provided he had a lot of experience.

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DoctorDv (author)2012-06-30

Its not always the voltage that is deadly. For example, it is said that a static electricity spark is 35,000 volts but at such a low current that you just feel a pinch where as 120 volts at 5 amps is definitely lethal. In the link below, it says that there are many factors determining the human body's resistance, but it is said to be between 300 and 1,000 ohms.  I hope this helps.

-Doctordv

van.physics.illinois.edu/qa/listing.php?id=19566

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onrust (author)2012-06-29

My rule of thumb is: All electricity is dangerous........ because I can't see it!

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Kiteman (author)2012-06-29

The best answer, I'm afraid, is "it depends".

According to wikipedia, high voltages change the way your body resists electricity (the dialectric of the skin breaks down), and the resistance to high voltages can be as low as 500 Ohms.

However, the same article also says that a DC current applied externally is a fibrillation risk at over 300mA.

But, be aware that if the electrodes penetrate the skin, currents as low as 1mA have been known to induce lethal fibrillations.

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Burf (author)Kiteman2012-06-29

+1
And the age and overall physical condition of the victim.

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steveastrouk (author)2012-06-29

YES YES.

Those levels are deadly, seriously deadly.

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