What is More Dangerous?

It's not the voltage but the current that is dangerous.

Though 50V AC would be more disruptive if you attached yourself to it.

I would say the CAPS LOCK KEY is very dangerous. Please press it one more time, and do not press it again.

Oh yeah, Rule 75.

Heard about it often. Rule 75........

What is it?

Rule # 75 was invented by one of the troublemakers here. It is informal and refers to posts, usually from a guest, that consist of a single, poorly constructed sentence which is difficult, if not impossible to understand.

Think "welder" silly Guest

its DC think RMS and don't ask elementary questions here.

Please explain ..what is V DC and VAC??

voltage has no effect but it is current.

Based on Dalziel Studies

All persons can safely withstand without ventricular fibrillation, the passage of a current with magnitude and duration determined by the following formula:

I = k/ (t)^0.5

where

k = (S)^0.5

where S is the empirical constant related to the electric shock energy tolerated by a certain percent of given population

Dalziel found that the shock energy that can be survived by 99.5% of persons weighing approximately 50 kg
(110 lb) results in a value of SB of 0.0135. Thus, k50 = 0.116 and the formula for the allowable body current
becomes

I = 0.116 / (t)^0.5

results in values of 116 mA for t = 1 s and 367 mA for t = 0.1 s.

So, if you want to test practically use above information and see your body resistance.

It really depends on many factors--primarily:

• the contact resistance of the skin at the wire (and things like is the skin wet, dry, ..., is there an open sore in the skin)
• is there a path for current flow (one of the standard pranks in coal mines I worked at was for someone to grab and hold on to the bare trolley wire (300 VDC) with good rubber boots, etc., and entice someone wearing standard (i.e., not electrical insulated) leather boots to do the same...
• what is the path of the current flow--across the heart is not a good idea

CR4 ADMIN: Moderated Post

Irrelevant Part of this post was deleted because it is related to a deleted post and would otherwise be taken out of context.

Treat all electricity like it will kill you, that way you know you will never make that fatal mistake.

There's no point in looking at numbers every time and deciding whether or not you are going to be sloppy with your procedure.

On the other hand, the careless ones will help weed out the herd.

Yep, I've had two acquaintances of mine get fried, both were, "professionals", that worked with electricity every day. Got used to working around it and got careless.

Unfortunately, in some cases, you only get to screw up once.

Like this?

Mr Edison and Mr Westinghouse had a violent dispute over this, a century ago. Mr Edison thought that "dangerous" alternating current (AC) was best for the "electric chair" method of execution, compared to his direct current (DC). (View "George Westinghouse" in Wikipedia). Perhaps this has biased perceptions......

A rule of thumb I and my fellow low voltage engineers used when working with high voltages was: If in doubt, keep one hand in your pocket while working on a circuit. That way if there is enough potential (voltage) to cause sufficient current (amperage) to hurt you, it's less likely to make it through your heart.

Note that this won't keep you from getting shocked, it just reduces the odds of a current passing through or near the heart.

I always remember the safety engineer's warning, when taking us into an ancient switch gear room with slate panels - and a fence as the "safety measures". He said "You do not have accidents at 11000 volts: you die!

Hmm. I'll pass on the 11 KV. For me, high voltages are 110 VAC.

Gives some meaning to my moniker.

Current is the killer. Voltage is the vehicle it rides in.

At 50V, you have to find it, grab it and hold it tight.

At 500V, you have to just touch it gently.

At 5,000V it reaches out and touches you as you walk by.

At 50,000V it's a drive-by killing.

That ignores the danger of fibrillation, which occurs at very low currents (and hence can occur with very low voltages).

With just a quick google, I found this article: Electric shock precautions. (http://pchem.scs.uiuc.edu/pchemlab/electric.htm)--and some randomly (i.e., not carefully) selected quotes:

Note that the 500 ohm resistance quoted once the skin is pierced or otherwise compromised is a maximum--try putting electrodes on either side of the heart and measuring the resistance, you will find it much lower. So how many volts do you need to push 100 ma. through 500 ohms? 50 volts

'

The actual resistance of the body varies depending upon the condition of the skin at the points of contact (moist or dry). The skin resistance may vary from 1000 ohms for wet skin to over 500,000 ohms for dry skin. However, once the skin is broken through (for example by the burning away of skin) the body presents no more than 500 ohms resistance to the current.

...

As shown in Figure 1, shock is relatively more severe as the current rises. At values as low as 20 milliamps, breathing becomes labored, finally ceasing completely even at values below 75 milliamps.

As the current approaches 100 milliamps, ventricular fibrillation of the heart occurs-an uncoordinated twitching of the walls of the heart's ventricles.

Above 200 milliamps, the muscular contractions are so severe that the heart is forcibly clamped during the shock. This clamping protects the heart from going into ventricular fibrillation, and the victim's chances for survival are good.

(2) AC is said to be four to five times more dangerous than DC. For one thing, AC causes more severe muscular contractions. For another, it stimulates sweating that lowers the skin resistance. Along that line, it is important to note that resistance goes down rapidly with continued contact. The sweating and the burning away of the skin oils and even the skin itself account for this. That is why it's extremely important to free the victim from contact with the current as quickly as possible before the climbing current reaches the fibrillation-inducing level.

The frequency of the AC has lots to do with the effect on the human body. Unfortunately, 60 cycles is in the most harmful range.

...

The frequency of the AC has lots to do with the effect on the human body. Unfortunately, 60 cycles is in the most harmful range. At the house voltage frequency, as little as 25 volts can kill.

...

Voltage is not a reliable indication of danger because the body's resistance varies so widely it is impossible to predict how much current will be made to flow through the body by a given voltage.

The current range of 100- to 200-ma, is particularly dangerous because it is almost certain to result in lethal ventricular fibrillation.

'

I'm lucky to be alive!

Back in my Navy days I worked in the engine room. Whenever something had to be worked on that involved electricity, it had to be, "tagged out", (shut off), all the way back to the source.

One day I was on the lower level, I had to climb down near the bilge to get a reading or something. There was a red tagged, open control box right where I was climbing down, with wires hanging out of it. 220 volt.

I was standing on some metal piping and not touching anything else, metal or otherwise, although I was surrounded by metal. My shoes had fairly thick rubber soles on them.

Since it was red tagged, I wasn't really thinking about the wires. Well, my arm touched one of those wires.............instantly, every muscle in my body contracted..............I was frozen in place. I could actually hear the humm of electricity in my head. Somebody had tagged it out and not got around to shutting off the power supply!

It only lasted a few seconds. Once I froze, I fell backwards........off the wire.

That one shook me up pretty good..........I can only assume, that had I been grounded, I would have been toast. It damn near qualifies as a miracle in my book.......it was a fluke that I wasn't holding on to a metal pipe with my other hand.

Do I have a healthy respect for electricity? You'd better believe it!

Standing in front of a train doing 50mph is more dangerous than either of those...

Depends on Technique