A shocking discovery - Page 1
Forum section: electronics / general

author: IanB
author_rank: Super Contributor
timestamp: March 04, 2012, 01:40:25 am
content: So I found that here in the USA, if you remove the cover plate from a wall outlet there are live metal parts completely exposed where you can touch them. What kind of crazy country is this? At least in Europe the terminal screws are recessed inside plastic surrounds so you can't touch them with your fingers. I'm going to take a picture of an American design so people can see it. I don't think there was any safety review at all...

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 04, 2012, 01:46:43 am
content: If you take the cover off a Schuko socket, while the screws are recessed, it is still possible to touch the metal parts and shock oneself. Or you can take the lazy way and just insert a couple of nails in the socket - no need to remove the cover for the shock.I also do not see any problem with that. If the outlet is damaged to the point that it is possible to touch the live wire, you should replace it and if you want to take the cover off, just switch off the power.

author: IanB
author_rank: Super Contributor
timestamp: March 04, 2012, 01:57:36 am
content: Right, so my next job coming up is to make a map of my house and label each wall outlet, then find out which outlets are connected to which circuit breaker. Someone stuck labels on the breaker panel, but there may be some fuzziness about exactly which outlets are covered. I want to be more precise. I suppose I will have to switch off each breaker one by one and then go around the house with a voltage detector to see which outlets got disconnected.In the UK it is much simpler. There are basically four ring mains: downstairs power, downstairs lighting, upstairs power, upstairs lighting; then extra circuits for cooker, water heater, garage/outside, and maybe electric shower or electric heating if installed. Luckily tumble driers plug into a standard 13 A wall socket and so there are no special circuits for that. And of course nobody needs air conditioning so there are no circuits for that either.

author: david77
author_rank: Frequent Contributor
timestamp: March 04, 2012, 02:01:20 am
content: Quote from: Pentium100 on March 04, 2012, 01:46:43 amThis is only true for older Schuko sockets/switches. The contacts on newer parts are designed to be fingerproof even with the covers removed.

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 04, 2012, 02:22:38 am
content: Quote from: IanB on March 04, 2012, 01:57:36 amPlug in a radio, turn it on, set the volume so you hear it when you are next to the circuit breakers. Turn the breakers off one by one until the music stops.There are a lot of circuit breakers in my house, but they are labeled and I always check the voltage before and after taking the cover off.Quote from: david77 on March 04, 2012, 02:01:20 amSoviet sockets are also dangerous with the cover off. Also, who the hell works on an outlet without turning off the power? As for accidental shocks, taking the cover off requires more work than putting a couple of nails in.

author: Psi
author_rank: Super Contributor
timestamp: March 04, 2012, 03:00:21 am
content: I think most of the wall plates available in NZ are recessed plastic but the original ones (which are in millions of homes) are all exposed at the back. I'm not aware of any law about new installations requiring the modem recessed type though.I think it was something PDL and other companies just did on their own when designing new ranges of plates.As i understand it, removing a wallplate is not something a typical person is supposed to be doing.

author: slateraptor
author_rank: Frequent Contributor
timestamp: March 04, 2012, 03:45:45 am
content: Quote from: IanB on March 04, 2012, 01:40:25 amWhat's so crazy about that? You shouldn't be handling live wires to begin with unless you're either qualified to do so or absolutely certain you know what you're doing, and a good nasty shock would significantly reduce the probability of any future repeat occurrences. By your argument, engineers ought to insulate every square inch of exposed metal on a power supply's primary to deter buffoons who decide to take the screws off some device's enclosure. Perhaps Americans aren't quite the liability that you suggest. =\

author: IanB
author_rank: Super Contributor
timestamp: March 04, 2012, 03:53:01 am
content: Quote from: Psi on March 04, 2012, 03:00:21 amIf safety rules were about what a typical person is not supposed to be doing, then most of the safety rules in existence would be unnecessary. Nobody should be doing anything dangerous.But here's the story with wall outlets in the USA.This is what the fixture looks like in the wall (cover removed with one simple screw):And close up, here is the fitting outside the wall:All the exposed metal parts on the side are live. The opposite side is exactly the same for the neutral wire.Here is a natural way to grasp it when removing it from the wall. Note how the fingers naturally fall on the live metal terminals. I am sure nobody has been required to produce any kind of safety case for this design.(It looks like the old fitting in the wall is a tiny bit safer than the new replacement...go figure.)

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: March 04, 2012, 03:53:16 am
content: ^ that wall outlet does seem to be a fairly poor design.Quote from: Pentium100 on March 04, 2012, 02:22:38 amPro electricians work on live wires all the time. I did on several occasions when repairing gas stoves.

author: Monkeh
author_rank: Super Contributor
timestamp: March 04, 2012, 04:06:37 am
content: American sockets leave a lot to be desired..QuoteThat's a very narrow view of domestic installations. Equipment such as tumble driers, washing machines, and the like should be on their own circuit or circuits in a properly designed installation. Also, none of those are 'ring mains', and only two are likely to be ring finals.

author: free_electron
author_rank: Super Contributor
timestamp: March 04, 2012, 06:33:09 am
content: fire your electrician !American style plugs and switches are supposed to be taped around with electricans tape after the terminals have tightened and just prior to pushing them in their wall boxes ! but it is not mandatory, only recommended....When i bought my house last year i replaced ALL outlets and switches ( they still had those ugly tumbler switches even though the house is only 8 years old )I used Cooper for all fixtures ( the charcoal style paddles with a silver trim ). taped all of them.What is more applaing is the fact that almost none of the american outlets have child proof sockets. you can just poke whatever in the holes. The coopers have a piece of plastic that refuses to budge unless you poke the plug exactly right into the socket. (Tamper resistant Outlet )

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 04, 2012, 07:06:45 am
content: Quote from: AntiProtonBoy on March 04, 2012, 03:53:16 amWell, until you come across a place that was miswired (so the wire that's supposed to be neutral is actually live) or somthing causes you to touch the live and neutral wired at the same time.The way I see it, there is no real reason not to turn off the power when working on an outlet (or a switch). On the other hand, I may poke around in a device with the power on in order to repair it (no way to measure the voltages if the device is turned off).

author: Randall W. Lott
author_rank: Regular Contributor
timestamp: March 04, 2012, 09:00:10 am
content: I always turn the breaker off when working on an outlet. There are too many things that could go wrong. Better be safe and make a little extra effort.All of the outlets in my home are exactly like the one you showed. There is no tape.When I was younger, I tried to pry the duplex outlet out of the box with a slotted screwdriver. I learned that the surrounding areas, such as the screw posts, can hurt. Granted, my house was built in the 1970's.

author: G7PSK
author_rank: Super Contributor
timestamp: March 04, 2012, 09:32:19 am
content: I have got one of those Levinton socket in front of me as I type the inclosed instructions do not mention winding tape arround the terminals It does refer to putting the "HOT" Black wire under the brass screws the "NEUTRAL" white wire under the silver screw and the 2Ground" Green or bare wire under the green screw. The cover is fixed with two screws. When fitted into the pattres there is not enough room for most adults to insert their fingers.There are many instances where if covers are removed you can access lethal voltages, when I remove the terminal covers on some of the power plants I can get both hands inside where there are six terminals with 415 volts at over 100 amps each, I once dropped a 19 ring spanner into the box when the plant was running there was a blue flash and the spanner was melted with only slight marking on the 12mm brass studs.What Is required is a world wide standard for voltage frequency and plug design.

author: wkb
author_rank: Super Contributor
timestamp: March 04, 2012, 10:05:04 am
content: Quote from: G7PSK on March 04, 2012, 09:32:19 amYes. Quite similar to world peace. And about as likely to happen

author: IanB
author_rank: Super Contributor
timestamp: March 04, 2012, 10:10:21 am
content: And one more thing: are you meant to mount the socket with the ground pin "up" or "down" (as pictured)?I have some low profile plugs where the cable falls downward with the ground pin below, and others where the cable expects the plug to be inserted in the opposite orientation.The most common convention seems to expect the ground pin downwards, but the manufacturer's installation diagram suggests the opposite.I wish people would make up their minds.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 04, 2012, 11:10:20 am
content: The part I don't understand is why you expect isolation? You had just removed the isolation, the face plate. You then sticked your fingers inside a thing that you know is connected to mains. Why do you expect a second isolation?It is not different from other mains powered things. You open the enclosure, you no longer have isolation from mains Would you just stick a finger in a random mains powered device?

author: IanB
author_rank: Super Contributor
timestamp: March 04, 2012, 11:23:57 am
content: Quote from: BoredAtWork on March 04, 2012, 11:10:20 amBecause it would be a better design that way?QuoteNo, I don't tend to go sticking my fingers in places with mains voltages present. But at the same time standards of safety should consider avoiding or removing reasonably foreseeable hazards. The face plate here is a very weak and flimsy cover. Double insulation is not a lot to ask for in the design of such a fitting.Consider tear downs of older gear on this forum. When people take the cover off a device you hear comments like "that's clearly an older design, those exposed mains terminals inside would not be permitted today". Standards change.

author: Psi
author_rank: Super Contributor
timestamp: March 04, 2012, 11:27:32 am
content: I take it the point was 110V ?110v isn't quite as dangerous as 240v, so they probably don't put such an emphasis on safety that we do with 240v in NZ/AU

author: Neilm
author_rank: Super Contributor
timestamp: March 04, 2012, 11:28:45 am
content: Quote from: G7PSK on March 04, 2012, 09:32:19 amhttp://xkcd.com/927/

author: wkb
author_rank: Super Contributor
timestamp: March 04, 2012, 01:09:50 pm
content: Quote from: IanB on March 04, 2012, 11:23:57 amYou mean: the world has changed to have more than the desired number of lawyers now? The proverbial: Can we claim damages from the vendor/his producer/his pet dog?In other words: trained people should know what they are doing. It is plain silly to work on live circuits if you very well know how you can prevent doing so.

author: billclay
author_rank: Regular Contributor
timestamp: March 04, 2012, 04:38:12 pm
content: Quote from: IanB on March 04, 2012, 01:40:25 amThe "safety" was the cover and the box protecting the outlet. You removed the safety.Would you open the cover on a plugged in power supply that was running (maybe with even a label that says "DANGER: HIGH VOLTAGE INSIDE") and touch the exposed capacitor terminals or transformer connections? No, you'd unplug the device and de-energize the caps first.

author: G7PSK
author_rank: Super Contributor
timestamp: March 04, 2012, 04:51:13 pm
content: Most of the British wall sockets the front cover plate is integral with the rest of the unit it is only with the industrial metal clad units that the cover is separate from the socket. If you pull the face-plate out the wires come out attached.

author: wkb
author_rank: Super Contributor
timestamp: March 04, 2012, 05:06:06 pm
content: Quote from: billclay on March 04, 2012, 04:38:12 pmAnd if you didn't you'd be granted a Darwin Award[http://www.darwinawards.com/]

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 05, 2012, 12:26:57 am
content: Quote from: billclay on March 04, 2012, 04:38:12 pmForget the power supply. Turn on a TV (or a monitor), remove the cover (disregarding the warning) and stick your finger (or an all-metal screwdriver) behind the anode cap. 25-30kV is more fun than 0.22kV. Somewhat insulated screwdriver will also work, but you will lose some of the voltage in the insulated handle and nobody wants that.

author: Shale
author_rank: Contributor
timestamp: March 05, 2012, 02:20:43 am
content: Quote from: Pentium100 on March 04, 2012, 07:06:45 amWhen I used to work on generators. I worked on Live 480 on a semi regular basis. As long as you take the proper safety precautions is not to big a deal. I worked around a lot of exposed 480, just part of that business.On a side note, i have been working on a home with 120 and grabbed a common that was hot. So been there, done that, not so fun, but lived to tell about it.If you have the chance to turn off the juice, then do so, but some times its not possible, and other times when working on mains, its just not convenient to turn off the juice. Ya I'm sure some one is gonna get upset and say there is always time to for safety and you should always turn off the juice. But in reality when working for an employer and the breaker to a circuit is across a building and down in the basement and your working on the 10th floor, its just not practical in some situations. So you may just wire up some little 120 plug, or 480 on some relay hot. I try not to make that a practice, and I take extra time a precaution when I know I am working with something that is hot, but it happens.

author: IanB
author_rank: Super Contributor
timestamp: March 05, 2012, 03:04:00 am
content: Half the trouble with working "hot" is those loose ends of live wires floating about. Sure, you can cap them to prevent them touching something, but you still have to remove the cap to connect them to a terminal, and during that exposed interval they might touch something they shouldn't and short out (or touch you and make you jump).I just spent the whole afternoon mapping out my house and figuring out which power outlets are on which breaker. And wouldn't you know it? Half the outlets I want to replace with new ones are on the same circuit as my computer. Which is a pain, as I never shut down my computer unless I really have to. Looks like I will have to... (shut it down again that is, not counting this afternoon's experiments)

author: Randall W. Lott
author_rank: Regular Contributor
timestamp: March 05, 2012, 06:40:08 am
content: Quote from: IanB on March 04, 2012, 10:10:21 amThey suggest ground pin up. Naturally, your thumb will tend to contact the top of the plug when handling it. I like them on the bottom because that's what I'm used to and I don't plan on handling plugs by their blades.

author: ronwoch
author_rank: Contributor
timestamp: March 05, 2012, 07:09:06 am
content: ^^ WHY oh why do we feel the need to protect people from themselves?Outlets in this country have been like that for many, many a decade. I dare say that if it were such a HORRIBLE safety concern, then our population would be significantly less. Are there better, safer designs out there? Sure. But really, let's think it through. Good parents teach their children not to touch a hot stove, a heater, or stick a penny or anything else into a socket. There are plug protectors for when the child is too young to grasp the point.Simple. DON'T touch that or it can hurt you. After they touch it anyway, the child is quick to learn that mommy or daddy was right. And they don't do it again. Also, it reinforces the concept that if mommy/daddy says that messing with something can hurt, it will!I'm only 26, but of all the many wall sockets I've seen in my life, only a few have had cracked faceplates. And ya know what? It still prevents you from touching the live wires! So 'flimsy' or not, THEY WORK! If it is so badly damaged that it DOES allow access to something dangerous, it takes a buck or two at the hardware store and a few minutes with a screwdriver to replace the damn thing.THIS is why lawyers make money suing companys like mcdonald's for not putting HOT COFFEE on the outside of a coffee cup.I mean, REALLY?!Ugh./ranting

author: Zero999
author_rank: Super Contributor
timestamp: March 05, 2012, 07:24:48 am
content: Quote from: Pentium100 on March 05, 2012, 12:26:57 amApart from the fact it's now 2012 and old CRT monitors are no longer made. The 25kV inside a CRT is much less dangerous than 230VAC because the current is limited to under 5mA and the anode capacitance is under 100pF

author: PeteInTexas
author_rank: Frequent Contributor
timestamp: March 05, 2012, 07:26:08 am
content: There is nothing shocking about this at all. What's next: "Shocking discovery! Stripping insulation exposes live wires!"

author: Simon
author_rank: Unknown
timestamp: March 05, 2012, 07:54:14 am
content: Quote from: IanB on March 04, 2012, 03:53:01 amI can't see a huge problem with that and am a firm believer in natural selection. I was wiring in Italy when I was a kid and got no formal training (as if the itis know what elecytrical safety is) and used my common sense and huge respect for a voltage that was 4-5x what is defined as lethal.

author: siliconmix
author_rank: Frequent Contributor
timestamp: March 05, 2012, 11:12:22 am
content: I can't see a huge problem with that and am a firm believer in natural selection. I was wiring in Italy when I was a kid and got no formal training (as if the itis know what elecytrical safety is) and used my common sense and huge respect for a voltage that was 4-5x what is defined as lethal.am a firm believer in natural selectionpmsl.working on live stuff.i had to kick a sparkey off a bread packing contraption once .he was stuck to it he was covering the red emergency switch which i couldn't get to.he was ok though because he said he was expecting it anyhow.

author: Simon
author_rank: Unknown
timestamp: March 05, 2012, 12:32:22 pm
content: haha

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 05, 2012, 03:02:28 pm
content: Quote from: IanB on March 05, 2012, 03:04:00 amBuy a UPS. It will also help keep the computer up when the power fails.Quote from: Hero999 on March 05, 2012, 07:24:48 amI don't particularly care that they are not made anymore. I have a few CRT monitors that work really well and intend on using them because LCDs suck (you only get one resolution and that resolution isn't very high either). OK, well, I care a bit because I will have to use old monitors instead of being able to buy a new one, but it is not that big a deal.While it may not be likely for a healthy adult to die from the anode cap, it still should hurt a lot and teach anyone about respecting devices high voltages.

author: SoftwareSamurai
author_rank: Regular Contributor
timestamp: March 05, 2012, 04:27:17 pm
content: Quote from: free_electron on March 04, 2012, 06:33:09 amUh...no.Electricians tape placed over the live terminals of a wall socket willnotstop any appreciable amount of electricity from flowing into your fingers, down your arm, through your heart, and out your toes.The only thing that will stop you from becoming the next electrically-cooked hotdog is to...turn off the power first!Look, working with household electric wiring is really easy. There are only 3 rules:1. Turn off the power.2. Turn OFF the power!3. TURN OFF THE POWER!(If you doubt rule 1, see rule 2. If rule 2 seems silly, always follow rule 3.)

author: Monkeh
author_rank: Super Contributor
timestamp: March 05, 2012, 08:21:43 pm
content: Quote from: SoftwareSamurai on March 05, 2012, 04:27:17 pmIt's not that I disagree with turning off the power, but I don't know what sort of tape you're thinking of, because mine will handle about 5kV per layer.

author: SoftwareSamurai
author_rank: Regular Contributor
timestamp: March 05, 2012, 09:14:14 pm
content: Quote from: Monkeh on March 05, 2012, 08:21:43 pmIt's not the volts, it's the amps that kill.A typical house line can supply between 15 to 20 amps before the breaker pops. (Assuming no GFCI breaker in line.) And let's not forget that we're made up of mostly water with lots of minerals and iron, which means we make a pretty good conductor. Yes, electrician's tape will prevent adirectconnection between your fingers and pure death, but I guarantee you it won't stop aninducedelectrical shock. And if you're unlucky enough to be grounded in some way, that induced charge can easily stop your heart. So yes, the tape will probably save you from instantly discovering the afterlife, but I'm not about to assume the tape makes it safe to grab with the power on.

author: MarkS
author_rank: Unknown
timestamp: March 05, 2012, 09:26:46 pm
content: Quote from: SoftwareSamurai on March 05, 2012, 09:14:14 pmMyth.

author: Monkeh
author_rank: Super Contributor
timestamp: March 05, 2012, 09:28:51 pm
content: Quote from: SoftwareSamurai on March 05, 2012, 09:14:14 pmI'd best stop touching all these flexible leads which are live, then. And no, it can supply a great deal more than that for the time required to harm someone.Feel free to show me one case of a 120V or 240V (Which is what I handle live and dead quite regularly) cable inducing fatal current in someone through several layers of PVC tape with a breakdown voltage in excess of 40kV per mm.And please remember that a shock does not equal death, and that GFCIs as you know them arenot100% reliable in operation nor in prevention of fatal shock.

author: ejeffrey
author_rank: Super Contributor
timestamp: March 05, 2012, 09:36:48 pm
content: Quote from: SoftwareSamurai on March 05, 2012, 09:14:14 pmEveryone who says this is wrong. While the statement is technically true-ish, it is only quoted by people trying to defend an incorrect statement.QuoteI have no idea what you mean by induced electrical shock, but this is nonsense. Electrical tape will protect you fine from a 230V/120V outlet. The main problem with it is the danger that it can easily be pushed aside or come loose and allow a direct contact with the live wire.

author: SoftwareSamurai
author_rank: Regular Contributor
timestamp: March 05, 2012, 09:38:58 pm
content: Quote from: MarkS on March 05, 2012, 09:26:46 pm<sigh> No, that's a fact. How else do you explain Tesla Coils? People touch "live" Tesla Coils and don't drop dead instantly. That's because a Tesla Coil generateshighvoltage,lowcurrent electricity.

author: Monkeh
author_rank: Super Contributor
timestamp: March 05, 2012, 09:40:38 pm
content: Quote from: SoftwareSamurai on March 05, 2012, 09:38:58 pmI've touched live 240V wires and not dropped dead instantly. And no, not while totally isolated from ground. Tesla coils are still fully capable of doing potentially fatal damage to you.

author: IanB
author_rank: Super Contributor
timestamp: March 05, 2012, 09:48:09 pm
content: Quote from: SoftwareSamurai on March 05, 2012, 09:38:58 pmNo, it's a myth born out of an insufficient understanding of electricity. It gets tiring to keep hearing such a wrong headed statement.There is more going on with Tesla coils than just low current. The high frequency has a lot to do with their properties. And don't ever delude yourself that Tesla coils are "safe". They can be incredibly dangerous if they are big and running at high power.

author: Randall W. Lott
author_rank: Regular Contributor
timestamp: March 05, 2012, 10:02:42 pm
content: Quote from: SoftwareSamurai on March 05, 2012, 09:38:58 pmPlease watch this. It explains exactly why it's not true.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 06, 2012, 09:19:56 am
content: Quote from: Randall W. Lott on March 05, 2012, 10:02:42 pmIn general,this video "tells it like it is".It's a bit unfortunate,though, that they show a CRT EHT connector with"Finger under here-dead!",as these supplies are most unlikely to cause a fatal injury.EHT supplies of this kind are fairly well able to supply enough current for their normal load,but the application of an excessively low resistance load across them (like a person),causes their output to drop radically,so that the initial current is quite high,rapidly falling to a very much lower level.--In other words ,their REGULATION is quite poor.(Just another way of looking at high internal resistance).You will find it extremely painful,you may have a heart attack,& if everything goes just right(or wrong),itmaygive you a fatal shock!I reiterate,however,it is very unlikely!Another thing that freaks out a lot of people is that CRTs maintain a charge after the supply is off,& the EHT lead is removed.Again,this residual charge is not dangerous,unless it makes you drop the CRT on your big toe !(By the way,many computer people have the habit of calling the whole monitor a CRT,& produce a lot of crud about them,such as"Your CRT has umpteen pounds of lead in it!"Anything about CRT monitors from computer sites should be treated with a very large "pinch of salt"!)Back to our point:If you were to start piddling around inside a 2KV DC supply in a radio transmitter,say,it's another story.Lower voltage,much better regulation (lower internal resistance),designed to supply Amps of current!You maywellbe "sent to your reward",but no doubt will be gratified to know that the fatal current followed "Ohm's Law"!About the insulating tape----it isINSULATINGtape,& that is exactly what it does!Many years ago,at work we tested two layers of PVC tape,up to about 12-13kV,so it is pretty good!Its main problem is that it is really only very good for wrapping around things where it can cover the whole of the conductive surface,with no gaps.Wrapped around a large power socket,it is quite difficult to obtain a really satisfactory wrap,so there may be gaps you could touch the "biteys" through!

author: G7PSK
author_rank: Super Contributor
timestamp: March 06, 2012, 09:55:31 am
content: I was told at school that it was possible to kill 500 people from the mains without blowing a 5 amp fuse if you got them all to hold hands, I am not sure if this is possible as I cannot find any reports of such an experiment being conducted.I once got a nasty shock from a 2 volt lead acid battery when connecting the terminals up.The maximum power allowed by law on an electric fence unit in the UK is 15 joules this is considered the maximum that will not be lethal to a normal person and I would assume that there is a safty factor there as well.

author: Rerouter
author_rank: Super Contributor
timestamp: March 06, 2012, 10:48:15 am
content: G7PSK, just as a baseline, nominal skin resistance limb to limb is about 12K,lets say its a hot day, everyones a little sweaty, that drags it down to about 8K,stick 100 8K resistors in parrellel and you end up with about 3A on a 240V supply nominal, thats 30mA per person, which is lethal, even on 110V its 1.375A which is ~14mA per person, and a current that some could walk away from, but still capable to kill, and this is only looking at a 3A, 5A could kill a lot more people, though each leg would recieve around the same current,if in series for 240V, 100 people on a good day only let 200uA pass, so even people with pacemakers would be safe

author: cybergibbons
author_rank: Frequent Contributor
timestamp: March 06, 2012, 11:33:07 am
content: Quote from: SoftwareSamurai on March 05, 2012, 09:38:58 pmOne example of something not happening doesn't prove that it can never happen.I don't get why there has to be a single mantra to deal with this. Fundamentally, only a small current is required through the chest to kill. It tends to require a high voltage to provide this current across a human body. Higher voltages are also more likely to cause secondary damage such as burns and entry/exit wounds that can also be fatal.My take on the socket - I've replace probably several hundred damaged UK sockets in a school with damaged or cracked face plates over the course of 5 years. Sometimes they are badly damaged, but the socket stays in the wall and it's impossible to touch a live part without using an implement. The US sockets look like a child could touch the live terminal.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 06, 2012, 02:11:51 pm
content: Quote from: G7PSK on March 06, 2012, 09:55:31 amYou are either the most sensitive person to voltage in theworld,on there was some kind of inductor in the circuit you were connecting to.

author: cybergibbons
author_rank: Frequent Contributor
timestamp: March 06, 2012, 02:27:41 pm
content: Quote from: vk6zgo on March 06, 2012, 02:11:51 pmStranded wire piercing the skin can cause small voltages to feel quite powerful...

author: G7PSK
author_rank: Super Contributor
timestamp: March 06, 2012, 06:37:39 pm
content: there was no wire, self capacitance is more likely

author: IanB
author_rank: Super Contributor
timestamp: March 06, 2012, 07:35:35 pm
content: Quote from: G7PSK on March 06, 2012, 06:37:39 pmIt just isn't possible to get a plain ordinary shock from touching a 2 V cell.Mostly what happens is that a pointy wire penetrating the skin hurts. If that pointy wire happens to be electified it hurts way more. 2 V will hurt a bit, 12 V will hurt like crazy. Psychologically it tends to make you jump out of your skin.

author: G7PSK
author_rank: Super Contributor
timestamp: March 06, 2012, 08:26:57 pm
content: I can assure you that at the time I got the shock there was no wires connected to the cell. I was just wiping the terminals with petroleum jelly after it had come of charge preparatory to using it. I have also had belts of car batteries in the past.

author: sacherjj
author_rank: Frequent Contributor
timestamp: March 06, 2012, 08:34:18 pm
content: Quote from: Pentium100 on March 05, 2012, 03:02:28 pmI've never seen a CRT that can touch my 24" Dell 1920x1200 IPS panel. I'm sure they were made. But I'm also sure they cost more than my first few cars. That isn't even a high res panel. Nothing like the 3,840 x 2,400 that are out there.

author: slateraptor
author_rank: Frequent Contributor
timestamp: March 06, 2012, 10:53:21 pm
content: Quote from: Randall W. Lott on March 05, 2012, 10:02:42 pmIronically, that video is off too.There are 2 ways to die by electric shock:1) death by ventricular fibrillation, and2) death by power dissipation.He's trying to justify death by point (1) using the physics behind point (2).

author: Unknown
author_rank: Unknown
timestamp: March 06, 2012, 11:20:03 pm
content: Yes, some of his arguments only focus on power dissipation, but his point that a high current 12 V supply will deliver insufficient current to cause ventricular fibrillation due to skin resistance at 12 V stands. I'm not sure about the minimum duration of the current to induce V-fib, but it's almost certainly much more than 1 us, since polarization of the heart is based on ion transport, and typical timescales are much longer.

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 06, 2012, 11:41:36 pm
content: Quote from: sacherjj on March 06, 2012, 08:34:18 pmI have Sony GDM-FW900 (24" widescreen): 2305x1440, maybe more if I set the timings correctly. My Dell P1130 (21" 4:3) supports up to 2048x1536, but 1600x1200 or 1920x1440 is good enoughI don't think there is a 24" LCD that can support higher resolutions. The 3840x2400 ones probably are something like 30".

author: Randall W. Lott
author_rank: Regular Contributor
timestamp: March 07, 2012, 01:39:10 am
content: Quote from: slateraptor on March 06, 2012, 10:53:21 pmI'm not an expert, but wouldn't you agree that the video has a better explanation than the whole "current kills, not voltage" saying?

author: slateraptor
author_rank: Frequent Contributor
timestamp: March 07, 2012, 04:51:08 am
content: Quote from: Randall W. Lott on March 07, 2012, 01:39:10 amI don't agree. Ventricular fibrillation is the main cause of death by electric shock, which is induced by sufficient current passing through the heart. It's not about frying your innards via energy discharge, which is what the video consistently alludes to.

author: Randall W. Lott
author_rank: Regular Contributor
timestamp: March 07, 2012, 05:58:55 am
content: Quote from: slateraptor on March 07, 2012, 04:51:08 amYou can die from burns or heart failure. Aren't higher voltages needed to penetrate your flesh to pass current through your heart? There's a huge amount of resistance unless the skin is penetrated. Of course, if you stab your chest with wires, you can reduce resistance enough to pass lethal current. High voltages will greatly reduce the resistance of your body.I had a professor that was working with a woman that touched a high voltage supply. The arc passed through her finger and blasted a hole through her elbow. They claimed that it was that her arm was bent that saved her. I'm not sure about the truth in that.Attaching jumper cables to each hand likely won't kill you, but attaching mains voltage could possibly.

author: IanB
author_rank: Super Contributor
timestamp: March 07, 2012, 06:12:28 am
content: Quote from: slateraptor on March 07, 2012, 04:51:08 amI didn't infer that from the video at all. The risk of ventricular fibrillation is higher when there is more energy in the electric shock, which could be a higher current for a shorter time or a lower current for a longer time. The video correctly talks about current in mA and energy in joules. Both are relevant to the amount of danger present. I'm not sure at all where you think the video talks about frying your innards?

author: slateraptor
author_rank: Frequent Contributor
timestamp: March 07, 2012, 08:26:10 am
content: I can wet my hands and hold the leads of a high-voltage, current-limited power supply all day, but nothing happens if the current is insufficient to induce the involuntary muscle contractions that lead to v-fib. Energy is irrelevant in this obvious scenario.Energy is indirectly relevant in a capacitor discharge model because of the impulse potentially exerted on the heart by combination of sufficient current offload and just the right RC time constant. That 11.2J is significantly greater than 0.0072J doesn't make a bit of difference for a sufficiently large time constant; the argument is donuts vs dynamite. A defibrillator pumps way more energy directly through the heart than the cap example in that video, yet it saves lives, not kills.

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 07, 2012, 09:17:01 am
content: Quote from: slateraptor on March 07, 2012, 08:26:10 amTry using it on someone who does not need it and it is very likely that you will kill him.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 07, 2012, 09:23:35 am
content: Quote from: slateraptor on March 06, 2012, 10:53:21 pmWe got taught an additional way, but years later health professionals told me they aren't sure it is possible. Toxic substances created by electrolysis of the blood during the shock, killing you days after the shock.And of course there is the proverbial falling off the ladder because of the shock.

author: Unknown
author_rank: Unknown
timestamp: March 07, 2012, 11:17:07 am
content: Quote from: BoredAtWork on March 07, 2012, 09:23:35 amDon't forget at HV and beyond, vaporisation is a real possibility! Whether the heart stops a microsecond before the smoke has never been accurately measured.

author: Blofeld
author_rank: Regular Contributor
timestamp: March 07, 2012, 03:52:32 pm
content: Quote from: slateraptor on March 07, 2012, 08:26:10 amThis is what Tony Kuphaldt has to say about it in his allaboutcircuits e-book (I don't know if it's true and I have no intention to try it out on myself):http://www.allaboutcircuits.com/vol_1/chpt_3/2.html"AC's alternating nature has a greater tendency to throw the heart's pacemaker neurons into a condition of fibrillation, whereas DC tends to just make the heart stand still. Once the shock current is halted, a "frozen" heart has a better chance of regaining a normal beat pattern than a fibrillating heart. This is why "defibrillating" equipment used by emergency medics works: the jolt of current supplied by the defibrillator unit is DC, which halts fibrillation and gives the heart a chance to recover."Anyway, I think the whole chapter on electrical safety is worth reading:http://www.allaboutcircuits.com/vol_1/chpt_3/index.html

author: Randall W. Lott
author_rank: Regular Contributor
timestamp: March 07, 2012, 04:24:59 pm
content: Speaking of the heart. It's an amazing organ because independently beating myocytes grow to form a unified mechanism to pump blood. The physics of the human body is incredible.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 07, 2012, 04:44:54 pm
content: QuoteNot quite any more - modern defibrillators use a biphasic shock, basically one cycle of AC.The principle is the same though - depolarise ALL of the hearts myo-fibrils and conducting system together and hope that organised electrical activity starts up once more.As tocausingfibrillation the main danger is an electric shock when the heart is trying to repolarise - in fact not just electrical energy can do this. Mechanical shock can do it as well which is why it isnota myth that a cricket ball landing on one's chest can kill.In some cases a shock is used to try to convert other rhythms back to normal such as certain fast rhythms which prevent the heart working well (eg ventricular tachycardia) - in this case the shock is synchronised to the "R" wave so as to avoid causing ventricular fibrillation.Although energies as high as 200J are used in de-fibrillation that's mainly because the body doesn't conduct nearly as well as you'd like in this situation - in open heart surgery paddles are used directly on the heart and only a couple of Joules is needed.To be honest I'm not sure that it's volts or amps but enough Jouleswillkill you.

author: sacherjj
author_rank: Frequent Contributor
timestamp: March 07, 2012, 05:03:30 pm
content: Quote from: Pentium100 on March 06, 2012, 11:41:36 pmIBM has a 22.2" at 3840x2400. If course, I think it is around $1.5k.Although that was probably more in the ball park of the GDM-FW900 when it was available.

author: G7PSK
author_rank: Super Contributor
timestamp: March 07, 2012, 09:53:52 pm
content: If you read this it states that a minimum of 1.25 amps is required for stunning pigs this is passed directly through the brain it does not cause death but epilepsy. Pigs are very similar to humans and are frequently used for training surgeons.http://www.grandin.com/humane/elec.stun.html

author: siliconmix
author_rank: Frequent Contributor
timestamp: March 07, 2012, 09:56:44 pm
content: haven't pigs got a really fatty skin though ?

author: grumpydoc
author_rank: Super Contributor
timestamp: March 07, 2012, 10:51:32 pm
content: QuoteDunno - they do have pretty massively thick skulls though.

author: entereev
author_rank: Contributor
timestamp: March 07, 2012, 11:39:42 pm
content: What's the average weight today? Aren't we nearing the pig fat thickness?

author: Pentium100
author_rank: Frequent Contributor
timestamp: March 07, 2012, 11:58:44 pm
content: Quote from: sacherjj on March 07, 2012, 05:03:30 pmNice, and it would show 1920x1200 correctly too. Hmm, I should try to get this resolution on my FW900 - in theory it should display it, at least in interlaced modeOn the other hand, Wikipedia says that IBM T221 needs a special video card and two DVI cables. If it can't support VGA, I would'nt be able to use it with my KVM switch (which is VGA/PS2).Maybe someday I'll buy something like that - assuming such monitors are still be made or at least the existing ones survive that long.

author: scrat
author_rank: Frequent Contributor
timestamp: March 08, 2012, 12:40:31 am
content: In the first part of the thread I see many people speaking about natural selection and the fact that a plug without its cover is not required to be safe at all.I'm not a safety fanatic, but it's quite handy to have a socket which cover can be removed without becoming very dangerous. Apart from the case of damaged parts, for example, with my plugs and wall switches I can remove the covers for painting better (just applying some tape, not even the insulating one, it's just for preventing fingers and brush from going near the contacts), or look for a broken wire, doing all of this with live on. Having to disconnect power would mean not having light in the meanwhile...When I was for a few days in the US, I found it strange that (in the country that has had the first absurd legal actions about safety) the plugs missed a very simple safety trick that is very common in Italy (and I think in many other countries): an insulation of the first piece of the pins (in the photo of an Italian standard plug, you can see the green part). In this way, it's impossible to touch the part when it's connected to the mains contacts. Another device that can save one (sometimes could simply be a child, instead of a stupid) from inserting any metal nails into the socket is a rotating piece of plastics, which blocks the entering unless the nails are two (in which case I agree with the natural selection idea). These things cost very little, but do their job, I think they're worth, without being excessive.That said, getting a mains shock can be quite harmless (especially if there's a GFI in the middle), and there's a heavy unbalance between perception of safety when speaking about electricity with respect to, for example, car circulation.

author: IanB
author_rank: Super Contributor
timestamp: March 08, 2012, 12:54:08 am
content: Quote from: scrat on March 08, 2012, 12:40:31 amI have seen that these are now available in the US as "tamper resistant" receptacles, although far from universal (they have been universal in the UK more or less forever).

author: Monkeh
author_rank: Super Contributor
timestamp: March 08, 2012, 02:54:10 am
content: Shuttered contacts have been required on UK sockets since the late 40s. Sleeved pins since.. I'm not entirely sure, 70s or 80s at a guess.You can insult the size of our plug all you like, but it's safe and robust.

author: PeteInTexas
author_rank: Frequent Contributor
timestamp: March 08, 2012, 02:57:40 am
content: Quote from: IanB on March 08, 2012, 12:54:08 amI came across thishttp://boards.straightdope.com/sdmb/showthread.php?t=239225Do electrical sockets and switches really have to be outside the bathroom in the UK?

author: 8086
author_rank: Super Contributor
timestamp: March 08, 2012, 03:18:08 am
content: Quote from: PeteInTexas on March 08, 2012, 02:57:40 amAnything except shaver sockets, I believe so. And as far as switches go, pull-cord or sensor activated ones are fine.

author: Unknown
author_rank: Unknown
timestamp: March 08, 2012, 03:24:57 am
content: Quote from: PeteInTexas on March 08, 2012, 02:57:40 amIn a nation where bathing is a fortnightly occurrence it would hardly even be an inconvenience.

author: PeteInTexas
author_rank: Frequent Contributor
timestamp: March 08, 2012, 03:41:14 am
content: Quote from: Uncle Vernon on March 08, 2012, 03:24:57 am

author: JonnyBoats
author_rank: Regular Contributor
timestamp: March 08, 2012, 05:22:22 am
content: Gee guys, as an American I am thinking that if someone is so stupid as to take the cover plate off the live outlet and start poking his fingers inside then perhaps he has what's coming to him ;-)I understand there are countries with more stringent safety standards, like at least one Scandinavian country where pedestrians are expected to wear a helmet and reflective gear.Perhaps it is our wild west heritage, but I kind of like being able to buy a wall outlet form less than $1 and install it myself rather than living in a country requiring me to use a super engineered outlet costing 10-20 (or more) times as much and requiring that it be installed by a licensed professional.Finaly I ask the question, have you ever heard of a documented case of someone taking the cover off an outlet and being electrocuted in America?

author: IanB
author_rank: Super Contributor
timestamp: March 08, 2012, 06:06:54 am
content: Quote from: PeteInTexas on March 08, 2012, 02:57:40 amStrangely, yes. It means, for example, that the common means of electrocution by dropping an electric fire or hairdryer in the bathtub while sitting in it is not possible(Although people have run an extension cord into the bathroom to listen to the radio and then electrocuted themselves with that.)It's odd that someone purporting to be a "UK EE" wrote that the UK mains voltage is 220 V. I smell fish(Although I smiled when I watched a US electrician on YouTube state that the mains voltage was 110 V and then proceed to demonstrate it with a meter. "Oh look, 120 V, just what we expect." )

author: Unknown
author_rank: Unknown
timestamp: March 08, 2012, 06:13:17 am
content: Quote from: JonnyBoats on March 08, 2012, 05:22:22 amI'm sure with a bit of checking you'd be able to find numerous examples where people had stuck there tongues on live conductors.But I'd have to agree you cannot legislate stupidity away. Every day people find new ways to die in Volvos.

author: Ajahn Lambda
author_rank: Regular Contributor
timestamp: March 08, 2012, 06:17:52 am
content: There are plenty of cases where children have stuck things in outlets, which is why these things are sold:That said, almost all of the AC shocks I've experienced haben't paused tooo buch brain dablage.Nah, seriously, it tickles or hums a bit, but that's when I'm not creating a low-impedance path to ground with another part of my body, either. Now, take a small child, and it'd be easily possible for them to take a metal object in one hand, place their other hand on a grounded object, and stick that metal into the hot side of the socket. I shouldn't have to tell you any more.IN MY VIEW, no system is inherently dangerous or safe. It's almost always the humans involved that make it so. Here in the US, those plastic outlet plugs are just one of those things expecting parents buy (or at least, intelligent ones do), and it's one of a boatload of things they do to keep their children safe.As for the "which way is up", I personally let the face plate determine it. If it's metal, the ground pin goes up, because if the metal plate somehow happens to fall forward (off the junction box, due to a stripped screw or mischievous morons), and something is plugged into the outlet, the plate won't become hot. Instead it will rest on or hit the ground pin FIRST, instead of the chance of resting on the hot blade. This is how ALL of the outlets on my lab bench are set up, and in some cases, it's allowed for easier cable routing -- many of my power surge suppression strips and instruments have molded, angled plugs.I'd suggest finding a copy of the NEC handbook, reading it, and understanding it, before thinking that any of the modern US electrical systems are 'dangerous'.EDIT: 120V is just a nominal value; 125, 115, and 110 VAC are sometimes quoted, too. It's almost always 123.4 VAC at my apartment, but anywhere between 112 and 124 VAC at my parents' place across the state. And just because I'm lazy, look at this:Quote

author: IanB
author_rank: Super Contributor
timestamp: March 08, 2012, 06:31:48 am
content: Quote from: SigEpBlue on March 08, 2012, 06:17:52 amRe: voltage drop under load. When I plug in my electric clothes iron all the lights dim in time with the on/off switching of the thermostat. I discovered this weekend the reason is partly that some dingbat daisy-chained 14 receptacles and 4 lights all off one 15 A circuit breaker in my house(It's even 14 gauge cable too, not even 12 gauge.)I've been examining the breaker box (rat's nest) to see if by any chance some circuits were paralleled up on one breaker (doesn't look like it), and looking to see if there are any junction boxes downstream (have not seen any yet). I'm trying to figure out if there is any way of fixing the situation without major surgery to the walls or ceilings.In the UK lights and receptacles are nearly always on different circuits, and the receptacles are usually on a 30 A ring main. The "dimming lights" phenomenon generally doesn't happen. (This is why UK plugs need to be fused, since the 30 A breaker will not protect a 13 A appliance cord.)IncidentallyI can attest that a 120 V shock tickles or hums a bit(bullshit!), but a 240 V shock is in a different league. I have not been daft or unfortunate enough to suffer one since I was a teenager, but it is really painful, definitely not ticklish.

author: G7PSK
author_rank: Super Contributor
timestamp: March 08, 2012, 08:36:29 am
content: Quote from: IanB on March 08, 2012, 06:06:54 amThe UK voltage used to be 240V but due to new EU regulations are 230V + - 6% and Northern Ireland is 220V but this will eventually rise The idea is for the whole of the EU to be standardized at 230V.

author: siliconmix
author_rank: Frequent Contributor
timestamp: March 08, 2012, 09:10:24 am
content: speak for yourself .i'm ripped.i feel tricity at 22 v .

author: Monkeh
author_rank: Super Contributor
timestamp: March 08, 2012, 01:13:04 pm
content: Quote from: IanB on March 08, 2012, 06:06:54 amActually, no. There are restrictions on type and location in wet areas, no blanket 'you can't have electricity in a bathroom' regulation exists.Quote230V ± 10%, actually. In reality this means just about everything is still 240V.

author: IanB
author_rank: Super Contributor
timestamp: March 08, 2012, 03:18:11 pm
content: Quote from: Monkeh on March 08, 2012, 01:13:04 pmBut if you go into the bathroom of any newer UK house the light will be either be on a ceiling mounted cord switch or the wall mounted switch will be outside the door. There will be no power sockets except for an isolated electric shaver socket. Electric fires if installed will be radiant heaters high on the wall with a cord switch.I have never seen any exception to any of these items.

author: G7PSK
author_rank: Super Contributor
timestamp: March 08, 2012, 03:37:48 pm
content: This is the regulations for bathrooms in the UK now they were changed in 2008 to allow sockets but only under certain conditions, size being one of them and as most UK bathrooms are small ( due to us poms supposedly only having a bath once a year whether we need it or not) you are unlikely to see sockets in said bathrooms."BathroomsThe installation of electrical devices in bathrooms and shower rooms is regulated in Section 701 of BS 7671:2008, and Part P of the Building Regulations. For such rooms, four special zones are defined, in which additional protection is required for electrical facilities:Zone 0 is the smallest cuboid volume that contains the bathtub, shower basin, etc..Zone 1 is the area above Zone 0, up to a height of 2.25 m above the floor.Zone 2 is the area above Zone 1 up to a height of 3 m, as well as the area that is horizontally within 0.6 m from Zone 1.Older regulations defined Zone 3 as the area above Zone 2 up to a height of 3 m, as well as the area that is horizontally within 2.4 m from Zone 2, from BS7671:2008this is replaced by the term 'outside the zones'. This includes any space under the bath or shower that can only be accessed with a tool.{ref bs7671:2008}Within Zone 0, no devices are allowed apart from suitable equipment and or insulated pull cords. In Zone 1, only separated extra low voltage (SELV) devices are permitted. Any AC transformer supplying such a device must be located outside Zones 0–2. The minimum required ingress protection rating in Zone 0 is IPX7 and IPX4 in Zone 1 and 2. If water jets are likely to occur, at least IPX5 is required in Zone 1–3. Otherwise, in Zone 3 and beyond, an ingress protection rating of IP20 is the minimum required. Equipment in Zones 1 and 2 must be protected by a 30 mA residual current device (RCD).Shaving sockets (with isolating transformer) are permitted in Zone 2 if direct spray from a shower is unlikely, even if they are only IP20. Before the 2008 regulations, such shaving sockets were the only sockets permitted in a bathroom or shower room. Since BS7671:2008 normal domestic sockets are permitted, at distances greater than 3m from the edge of the zones, providing the circuit is RCD protected. As the new regulations also require all general purpose sockets not for use by skilled or instructed persons to be RCD protected, this effectively permits normal wiring in the larger bathroom. (Earlier British wiring rules in bathrooms used to be far more restrictive, leading to British peculiarities in bathrooms such as the use of cord switches. The 2001 edition of the Wiring Regulations is more flexible now, placing restrictions on bathroom installations that are now more similar to those in other European countries. )"

author: cybergibbons
author_rank: Frequent Contributor
timestamp: March 09, 2012, 01:27:35 pm
content: The best thing about the old regs was that they were so strict that you ended up wit the situation that a bathroom was either completely by the book, or totally batshit crazy dangerous. I've actually found an extension socket under a bath, with an electric shower plugged into it.

author: Ajahn Lambda
author_rank: Regular Contributor
timestamp: March 09, 2012, 02:07:25 pm
content: You haven't lived until you've had to deal with knob & tube wiring.

author: SeanB
author_rank: Super Contributor
timestamp: March 10, 2012, 10:56:34 am
content: The harmonising of the UK mains was done by changing the voltage limits. It was 240V plus or minus 10 percent, and afterwards it was 230V plus 10 minus 6 percent. Thus there was no need for the utilities to change anything ( think of the cost of replacing every distribution transformer at the same time as an example) other than how much they were allowed as a variation. They have only to take care not to give too high a voltage now, and this only under low load conditions. This can be handled by the standard substation equipment easily, and had no cost.Here in South Africa there are still a few pockets of century old systems, which are nominally 240V. they will not be changed out but have the high voltage limited to not exceed the spec. At work the mains is around 234 to 238V, mostly as there is a substation of 200kVA feeding it on site. Nice low impedance feed.

author: G7PSK
author_rank: Super Contributor
timestamp: March 10, 2012, 03:25:42 pm
content: I Have a friend that used to live in a big old country house that before mains ever came along had its own power plant. On one occasion I went into the loft and found that the lights were wired with bare copper conductors about 2.5 mm dia held on wooden and ceramic battens this had been connected as is to the mains when the rest of the house had been rewired to the standards required in the early 60's when the mains power arrived. The first thing I did was find the fuse for the circuit and remove it.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 10, 2012, 03:49:06 pm
content: Quote from: G7PSK on March 10, 2012, 03:25:42 pmAnd the next thing your friend did when figuring out the lights in the loft didn't work was to improvise a fuse with a nail?

author: IanB
author_rank: Super Contributor
timestamp: March 10, 2012, 04:53:50 pm
content: Quote from: G7PSK on March 10, 2012, 03:25:42 pmAnd as long as the system was electrically and mechanically sound it was perfectly OK. The main danger would be contact or shorting by foreign objects or people against uninsulated conductors. If the wiring was placed in an inaccessible location this would not be a great danger. You just need to be aware and have the wiring upgraded to modern standards at the earliest opportunity.QuoteI can see you are not a friend anyone would want to invite round to their house. With friends like you, who needs enemies?

author: G7PSK
author_rank: Super Contributor
timestamp: March 10, 2012, 06:31:43 pm
content: Quote from: IanB on March 10, 2012, 04:53:50 pmThe light switch was on the end of this circuit just inside the loft door and it was easy to touch the bare wires also as it was a big old house there was bats and birds in there , And no the friend did not find a nail she called an electrician and had the rewiring done.

author: cybergibbons
author_rank: Frequent Contributor
timestamp: March 10, 2012, 08:07:08 pm
content: Quote from: G7PSK on March 10, 2012, 03:25:42 pmSeen this a few times before. Work of art, strung around above the ceiling. I couldn't work out the rationale behind it as the wiring down to the switches in the rooms was insulated - maybe the insulated wire was prohibitively expensive.The copper on these ends up incredibly brittle after so many years in use. I think the cooling and heating causes work the spans to increase and decrease in tension, causing gradual work hardening. Combined with lower purity of copper than now.

author: IanB
author_rank: Super Contributor
timestamp: March 10, 2012, 08:15:03 pm
content: Quote from: cybergibbons on March 10, 2012, 08:07:08 pmInsulation was generally unreliable in the days before plastic. I think wire insulation had to be made out of rubber and protected with a woven cotton covering. The rubber could become brittle and crack with age and allow the conductors to touch inside the cable. Not good. Hence the use of insulated wires would be kept to a minimum.With the porcelain insulators I think the idea was to keep the out and return conductors well separated so it was hard for anything to touch both at the same time. In an isolated and unearthed system touching a single wire was unlikely to create a hazard as it wouldn't complete a circuit. Porcelain and air made for a better and more reliable insulating system than a rubber sheath. (As it still does today: look at the number of power distribution systems that still use porcelain and air as the insulation mechanism.)QuotePerhaps the wires should have been installed with some lack in them rather than being pulled tight. Maybe not all electricians knew about that when installing the system?

author: Monkeh
author_rank: Super Contributor
timestamp: March 10, 2012, 08:28:35 pm
content: Quote from: IanB on March 10, 2012, 08:15:03 pmYou'll find that's only for high voltage installations where insulation isn't practical. Modern materials have much higher breakdown voltages than air, the problem is you need a lot of them when dealing with tens and hundreds of kilovolts. Air is easier.

author: IanB
author_rank: Super Contributor
timestamp: March 10, 2012, 08:31:10 pm
content: Quote from: Monkeh on March 10, 2012, 08:28:35 pmAnd cheaper.

author: Monkeh
author_rank: Super Contributor
timestamp: March 10, 2012, 09:00:26 pm
content: Quote from: IanB on March 10, 2012, 08:31:10 pmPrecisely. It's also insane for domestic use.

author: G7PSK
author_rank: Super Contributor
timestamp: March 10, 2012, 09:32:50 pm
content: Copper age hardens, also older wire had more oxygen left in during manufacture even today a lot of copper used in wire contains a lot of oxygen, I once tried using electrical wire as filler material for welding copper as I did not want to have to buy a 7KG pack just for one small job, big mistake it bubbled up like aero chocolate due to the oxygen and other gas in it had to bite the bullet and buy the correct filler wire still have most of it 15 years later.

author: SeanB
author_rank: Super Contributor
timestamp: March 11, 2012, 01:49:17 pm
content: I did the same, using wire from an old transformer. Worked a charm. Now I but the correct rods and silver solder.

author: IanB
author_rank: Super Contributor
timestamp: March 13, 2012, 01:53:34 am
content: Quote from: IanB on March 08, 2012, 06:31:48 amI hereby retract my words and state that this is not true. A 120 V shock bloody hurts. In the spirit of inquiry I tested what happens with dry fingers touching clean metal electrodes. If you are tempted to try that--don't! It is rather painful.I should note for the record that the test was done with finger and thumb of one hand and my chest was not in the current path. I may be crazy, but I am not suicidal

author: Monkeh
author_rank: Super Contributor
timestamp: March 13, 2012, 02:02:54 am
content: Quote from: IanB on March 13, 2012, 01:53:34 amNow across your body, it might tickle due to the increased resistance and thus lower current. Through a hand.. even 12V hurtsYeah, I may have grabbed one of those little lamps with 12VAC running up the telescopic arms with wet hands one day..

author: Lawsen
author_rank: Frequent Contributor
timestamp: March 14, 2012, 12:25:42 am
content: That outlet design and wiring are very common here in the U.S.A. Those are single outlets in a shallow depth box for single ROMEX or solid copper cable. You could replace it with a nonconducting, deeper plastic box. These are available from the Home Depot. You fortunate to have ground connector. Many older houses and places have no ground. American voltages are lower, 120 V AC. I am not an electrician, but what you shown is just very common here in the U.S.A. and North America. If you need to parallel wire another outlet, then it will need a raiser plaster metal box with an opening at the back to screw into the existing box in the wall to accommodate more wires. I have done this before with shallow depth, tight fitting in the wall outlet box like you shown in your pictures. These are not my favorite, but very common.