Here’s a neat page on SparkFun that discusses that very topic:
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My great grandfather was one of the first master electricians, and he got cancer from chewing wire insulation. They used to all chew it and called it “electricians gum”. I still have some of his hand forged electricians tools, they are so much better made then anything you can commonly find these days.
Back then there were three types of insulation, paper, cloth, and this thick black stuff that they’d chew. Often times wire wouldn’t even be insulated at all and be run bare, they’d attach it to ceramic insulators on metal posts in the walls. Due to resistance sometimes wire would heat up and melt at the 90 degree bends in the walls starting fires. Also rodents in the walls would get fried and smell something awful.
Anyway, he also used to carve things out of wood, i have a collection of birds he carved. he was a really neat guy.
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God I know that tingle…
The 4.5V batteries are also testable this way. The CR2032 3V lithium ones too.
Avoid licking the phone jack. I did it once when in a real pinch in an office with a malfunctioning fax machine and no voltmeter on hand. The 40-60V DC is a bit too much.
Or do it as a backup, after checking with an instrument. That way you make sure the instrument did not lie to you and then cackle from its case “Liar liar hands on fire!” when you touch the live metal.
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Reminds me of this incident:
Van der Graaf is on the demonstrator bench, churning out 10cm sparks periodically (feeding a small ball with a capacitor and a parallel meter reading 10uA). The fluorescent tube over the bench has been flickering.
Our physics teacher gets annoyed by the flickering, stands on a stool and removes the fluorescent tube.
Unfortunately it is six feet long and the far end droops to within about 15cm of the VderG. There is a spark, the tube briefly flashes, our physics teacher drops the tube (which doesn’t break) on the bench, gets down, removes his glasses, polishes them, turns to us and says “that was a demonstration of charge transfer to a body capacitively coupled to earth.”
It’s called SELV (safety extra low voltage) but you are still not supposed to put it across internal parts. It can cause severe damage; the PTC thermistors in the phone circuit and the lightning arrestor are there to protect the network, not you.
My parents let me have an old steel water tank at the bottom of the garden to carry out experiments in. They moved while I was away from home and I have sometimes wondered what the new owners made of the water tank with the blackened interior and the oddly shaped lumps of metal in the sand lining. The previous owner of our house had in fact been an explosives expert at ERDE (Explosive research and development establishment), so I guessed if they were interested enough to look back at the land tenure records they might put two and two together and get the wrong answer.
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Well a bomb proper no. I have been in on the making of questionable pyrotechnic materials though.
Domestic possibly, but actually a lot of industrial lighting is 270V. I know because I worked with Motorola on designing a failsafe for industrial compact fluorescents, as all the existing ones were rated 230V only (European standard.)
Fun off topic fact; in some places in the South-West as much as a third of a factory or office aircon load is simply removing the heat from the lighting, because the lack of natural light means that it is on all day. This means that half the facility electrical consumption is simply waste.
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I like old war stories (yours, japhroaig’s, shaddack’s, etc.). I usually want more detail. (For example, how did a guy come to touch 480v three-phase?)
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Never got the specifics, but even I have been within spitting distance of exposed copper Rods (that shit ain’t wire) carrying that kind of current.
Geez, it gives me chills. But I’ll take a pic the next time I’m at the shop. 
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In some high voltage labs you cannot wear any jewelry and must keep your right hand in your back pocket at all times for exactly this reason. You get good and doing everything with just your left hand.
Indeed. black helicopter officials.
Personally I blame Hollywood, which has taught so many possessors of sub-+1sigma IQs that anything with a red LED numeric display is a bomb. Back in the day before LCD panels I worked for a company where we used HP LED displays a lot in our equipment - I guess at the time Hollywood’s idea of “bomb” would have had a lighted string fuze.
Totally correct. In fact at one time I had a laptop with a metal lid which obviously had a slightly defective power supply. You could definitely feel a current with a hand on the lid. Reversing the live and neutral wires in the (UK, 3 pin) plug fixed it.
Who needs the Vietnam war? A number of my teachers had been involved in WW2, which was probably why they didn’t seem to worry about anything. Another physics teacher quote: “We’re not supposed to go above 5000V because of X-rays. Anybody afraid of X-rays go to the back. Right, we will now crank up to 10 kilovolts.”
Our chemistry teacher also let us do an experiment with a very small quantity of picric acid which I don’t intend to go into here. What were we doing with picric acid in the store room? No idea.
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The version I heard was that you use your right hand (so the current travels down the right side of your body and misses the heart) and you keep your left hand in your pocket (so any involuntary muscle spasms don’t cause it to flail into contact with the wire).
The advisability of doing touch-tests on current that you believe is powerful enough to cause full-body spasming was not mentioned.
(Also, seems to me that “stupid things to do with electricity” is perfectly on topic to this post.) 
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What interests me about this is that Woz’s gizmo was set up to tick faster when the door was opened, which suggests that the bizarre notion that a bomb will tick faster/louder/sound an alarm/generally draw more attention to itself the closer it gets to detonating dates back to the '60s at least. I thought it was a more recent TV/Hollywood thing.
That’s pretty much the version I heard. The back of the hand for lighting equipment always seemed sensible to me as well. I’ve been in a few environments with high voltage DC where the operating rule was: don’t point at anything.
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Which is utter nonsense because, in fact, your heart is pretty close to centre.
To quote an expert from H&SE: “There is no known lower level of current through the body which is safe.”
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