leaving conductors exposed

Wrong, wrong, wrong, wrong, wrong. The voltage has nothing whatever to do with electrocution (other than affecting how much current flows). ONLY THE CURRENT MATTERS.

You cannot be killed "with a few milliamps". The thresholds are known, and the lethal level is at about 100mA through the heart.

I can't believe the participants in /this/ group aren't more familiar with electrical safety.

That bit is correct.

The actual amount will vary from person to person. That may well be an average. How many 'milliamps' on average does 'your' electric chair seek to achieve to be fairly certain of killing someone without blowing them apart?

Electrical safety standards vary between countries. And over the years. The only truly safe advice is not to touch anything live.

That's one of the problems with electric chairs -- they don't work the way they're supposed to. They do a better job of slowly frying the criminal, rather than quickly stopping his heart.

I'll have to write a new version of Gilbert... "The criminal fried..."

I was talking about safety, not safety standards or regulations.

Human skin has a resistance between 1K and 6K, and that resistante varies with the voltage aplied to skin. This table supplied by the IEC indicates that human skin electrical resistance varies as follows:

Voltage 5% 50% 95% 25 V 1,750 =CE=A9 3,250 =CE=A9 6,100 =CE=A9 100 V 1,200 =CE=A9 1,875 =CE=A9 3,200 =CE=A9 220 V 1,000 =CE=A9 1,350 =CE=A9 2,125 =CE=A9

The 5%, 50%, and 95% columns represents the distribution of the population percentile per measurement.

Now lets assume that you have a voltage source of 24V. According to the above table your body impedance can be anywhere between 1,750 and

Now lets repeat the calculations supossing that we have a voltage source of 60V. Using again the table, and taking the lowest impedance possible (1200 ohms), the amount of current that will be drawn by the human skin would be 50 mA. OK, for sure that will be a painful experience but no one will get killed from a 60V source... except if the person is wet. In that case, the impedance will be lower.

The point I am trying to make here is that while is true that a 100 mA current is lethal, you have to provide a voltage level high enough to your body in order to make draw 100 mA. Voltage levels under 60V will not kill anybody unless the person decides to put electrodes under the skin, or the skin is wet.

That's a way-low value. Try grabbing the probes of a DVM.

The actual resistance varies with the skin's wetness, the area covered, and whether the skin has been penetrated.

nd

Certainly a DVM will show a body impedance of 20K or more, but please take into account that a DVM will, at most cases, apply 1.5V or 3V to the test probes, and skin impedance is inversely proportional to the voltage applied to it.

See this article:

"The voltage necessary for electrocution depends on the current through the body and the duration of the current. Ohm's law states that the current drawn depends on the resistance of the body. The resistance of human skin varies from person to person and fluctuates between different times of day. The NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as

The International Electrotechnical Commission gives the following values for the total body impedance of a hand to hand circuit for dry skin, large contact areas, 50 Hz AC currents (the columns contain the distribution of the impedance in the population percentile; for example at 100 V 50% of the population had an impedance of 1875=CE=A9 or less):[10]

Voltage 5% 50% 95%

Notice that depending on the amount of voltage applied to the skin, it resistance decreases. That=C2=B4s why a DVM will show a higher impedance than the one that is published in the table.

Summarizing: we agree that current is what kills, but in order to make your body draw that amount of current, you need a high enough voltage. Voltages under 60V are unlikely to kill anyone, unless the person is applying electricity directly through an open wound. Just do the math.

A humman body doesn't 'draw current'. It 'passes current' if you are in a circuit.

;-)

Indeed. To you or me it seems so simple.

Then there's me. Thick skinned. As you have to be to post to a US group from the UK.

I'd guess they are measuring through the skin - from front to back as it were. But of course it varies in thickness according to where it is in on the body.

u are

Certainly. My mistake.

In message , lsmartino writes

It's not a mistake at all. To 'draw current' is a common figure of speech. A resistor, connected across a battery, by passing current, will 'draw current' from the battery.

BTW, I know that an 8 amp charger won't put any more current through me than a one amp charger. Maybe I don't hold both claimps at once because they are big and ugly and and "zinc"-coated and seem dirty even when they're not, and much harrder to hold in one hand than the other little ones, and they are on separate wires instead of two-conductor wire that splits only a few inches from the clamps, like he little charger.

The body gives thousands of ohms resistance, even when one's fingers are wet.

Has anyone every been killed by 12-volts, DC or AC? I doubt it.

Thanks for recommending the Powermid pyramid remote extender. I got one and it works great. I'm going to get more for other rooms.

I knew about it, but hadn't had a personal recommendation before.

Sort of ir>> Certainly you can be killed with a few milliamps,

Except that the current is directly proportional to the voltage, so I don't think it's fair to say the votage ahs nothing whatever to do it with it.

And you can only apply voltage. You don't know how much current will go through most things until there is a voltage across it either from an ohmmeter or some power supply.

No offense meant, but I'm reminded of a JHS science teacher who said that water had nothing to do with rust, because the formula for rust production is Fe + 02 = Fe02 (or something like that) and water isn't in it. Even though everyone can tell that wet things rust much more than dry things.

Other than this, I agree with your posts.

Well... I didn't buy it. The issue is not about the buyer's ability to determine the safety of a Chinese lamp. The issue is about the certification agencies who have the device in their lab for qualification. Their JOB is to protect me from harm. They should not have qualified such a device. You may feel otherwise, that's your right.

That's a "creative" interpretation.

To get current, you must have volts. Power = volts x amps. So, where does that power end up? And how do you rationalize a useful distinction between "drawing" and "passing"?

That statement suggests a misguided interpretation of "certainty". I doubt you've considered ALL possibilities. "unlikely" might be a better word than "cannot" for use in that sentence.

I've got three of those design lamps here. Bought many years ago. Didn't know they'd come back into fashion. I'm no more worried about using them than I worry about having a PP3 battery with the terminals exposed...

You're right in principle, but it's difficult to think of /any/ situation in which 14 volts could pump enough current through a human body to kill its owner. You'd need a net resistance (across the heart) of 140 ohms. Not likely.