Plug safety

March 31, 2008 2:34 PM

If a plug is not fully in its outlet, and you touch one of its prongs, will you get shocked?

Sorry for the stupid filter on this one... just something I've always wondered and never really knew for sure.

posted by cgs to science & nature (32 comments total)

Yes. If the prongs are in the outlet far enough. I've been shocked this way.
posted by lain at 2:36 PM on March 31, 2008

It depends on how far in they are, but yes. I have been shocked by carelessly pulling a plug out half-way and then carelessly touching the exposed prongs.
posted by muddgirl at 2:40 PM on March 31, 2008

Yup. Feels like someone kicked your arm.
posted by Burhanistan at 2:40 PM on March 31, 2008

Only one of the three is hot, but if that one is far in enough to make contact with the inside of the outlet, then of course. Go spend 50 cents on an outlet at HD one day an pull it apart with pliers. You'll know 100% more about how it works after that.
posted by Patapsco Mike at 2:41 PM on March 31, 2008 [1 favorite]

Yes, but these days it's getting more and more common to see the prongs insulated to prevent this: GIS example. I expect it will be pretty much standard in a few years.
posted by -harlequin- at 2:42 PM on March 31, 2008

Yes. I've been shocked this way.
posted by limeonaire at 2:48 PM on March 31, 2008

yes, if it's plugged in, the circuit is complete, and if you add yourself to that circuit you'll feel the buzz.

Don't worry about the "stupid filter" it's far better to test this out on the green then with a wet finger. To illustrate, a former friend of mine tested this by holding a paper clip in his mouth and sticking it into the outlet.

Hypothesis:
This will shock the shit out of me.
Procedure:
Stick face/tongue in electrical outlet.
Observations:
That felt like getting kicked in the face.
Conclusions:
Sticking face in circuit can and did shock the shit out of me. No further testing needed.
posted by JimmyJames at 2:49 PM on March 31, 2008 [5 favorites]

yep. has happened to me, too.
posted by gnutron at 3:04 PM on March 31, 2008

I did this when I was a kid, plugging in a VCR. My arm went all tingly for about a half hour. Good times.
posted by backseatpilot at 3:22 PM on March 31, 2008

Ooo, I have long wondered about this... Is it the same in the UK with the different sockets?
posted by cluck at 3:27 PM on March 31, 2008

It also will shock you if you position your finger between the prongs, and THEN plug it in.

And if you convince your little sister to do the same thing with her finger, it can create a shock on your backside when your parents find out.

Also, if you put a pair of scissors in between the prongs and plug it in, you can blow a fuse.

Not that I've done any of these things.
posted by SpacemanStix at 4:23 PM on March 31, 2008 [1 favorite]

I am surprised how many incorrect answers there are here!!

Your original question asked "If a plug is not fully in its outlet, and you touch one of its prongs, will you get shocked?"

I am assuming :
the plug is not fully in the outlet, but IS in far enough so both prongs contact their seats in the outlet ( and whatever is on the end of the wire DOES operate ).

-- In this situation, if you only touch ONE of the prongs .. NO you WILL NOT get shocked!.

--- If you touch BOTH prongs , YES, YOUR FINGER WILL GET SHOCKED


You have to complete the circuit .. either by touching BOTH prongs, or a prong and a common ground (can be the third grounding prong, OR something nearby that is grounded properly to the same electrical system.)


Think about it this way ... you have a voltage meter. You touch ONE of its ends to a live wire. The other end just hangs in the air. What does the meter read? Nothing. because it is not a complete circuit!
^{(( Technically you may get very small readings , because some of the electricty can travel through teh air. But at normal 120 (or 220) volt household voltage .... full conducting arcs are not easy to accomplish at all, and not enough voltage will travel through the air for you to feel a shock. ))}
posted by Ryaske at 5:02 PM on March 31, 2008

Now we just need jjg to test this one out for us, just to be 100% sure. On second thought, I think we've settled this on our own...
posted by zachlipton at 5:08 PM on March 31, 2008

Here is a great reading that will clear everything up for you (and everyone else) about shock current paths

http://www.allaboutcircuits.com/vol_1/chpt_3/3.html
posted by Ryaske at 5:08 PM on March 31, 2008

p.s. .... one last thing to keep in mind. That reading i linked you to regards DC current, which does not change direction.

With AC current (constantly changing direction- the same stuff that runs through your house) there is not a common negative ground like there is in high voltage DC systems. In AC there is an External ground. Since neither pole in an AC plug is "locked to ground", getting between the ground prong and EITHER pole WILL shock you (if the ground is a good ground!).

So with AC - higher chance of being shocked.

I think that about covers it. I highly recommend that site i linked to .. its how i got started in electronics
posted by Ryaske at 5:19 PM on March 31, 2008

-- In this situation, if you only touch ONE of the prongs .. NO you WILL NOT get shocked!.
Don't you complete the circuit by being grounded yourself? You become the shortest path to the ground--while your multimeter in the same situation is totally isolated...
posted by ddaavviidd at 6:02 PM on March 31, 2008

Ryaske: dangerous advice there.. you absolutely can get shocked, even fatally, depending on what the rest of your body is touching.
posted by TravellingDen at 7:29 PM on March 31, 2008

Seconding the bad answer by Ryaske. You can touch one and be shocked because your damp feet are completing the circuit to ground, or your damp hand on the floor, or your elbow against the wall. Mmmmm, so many paths that go through the chest cavity, hooray!
posted by intermod at 7:43 PM on March 31, 2008

Rysake is talking bollocks, if you'll pardon the expression - as others have pointed out, if you create a circuit from the "hot" prong you most certainly will get a shock. Your response falls well into the "stupid enough to be dangerous" category.

As for UK plugs, most modern plugs have semi-insulated Live and Neutral prongs - pulling the plug enough out of the socket to touch the exposed live pin and it'll almost certainly be disconnected from the socket seat.

Not that I'll be volunteering to test the theory. A piece of advice my dad once gave me - "working with electricity is perfectly safe, as long as you respect it. The moment you don't is the moment it'll kill you".
posted by Nice Guy Mike at 7:47 PM on March 31, 2008

Absoutely by NO means am I saying TRY IT !! DO NOT !! My explanation is just to satisfy the posters curiosity ...

And I should have made more clear my othe assumtion - that you are perfectly isolated from everything else around you. ( I.e. in a typical house .. you are standing on a carpet, vinal floor , tiled floor , wood floor , etc. )... where there is no ground that you do not know about (perfectly possible of course!!)

So while touching one prong (either prong .. doesnt matter neutral or hot!), and are isolated from everything except that one prong; In that case, and only that case, are you "not shocked".

As for testing the theory .. it has been done in front of me countless times by someone quite a bit more brave then me (to prove the very point). I always cringed .. and will not ever try it myself ... and I advise you do not either!

But you have to touch both prongs, or a common ground, or otherwise complete a circuit, in order to be shocked .. just like in that link I posted ... which lays it out very clearly
posted by Ryaske at 8:05 PM on March 31, 2008

And I should have made more clear my othe assumtion - that you are perfectly isolated from everything else around you. ( I.e. in a typical house .. you are standing on a carpet, vinal floor , tiled floor , wood floor , etc. )... where there is no ground that you do not know about (perfectly possible of course!!)

So while touching one prong (either prong .. doesnt matter neutral or hot!), and are isolated from everything except that one prong; In that case, and only that case, are you "not shocked".

What?

This may be a transatlantic misunderstanding type thing, but are you seriously saying that a carpeted floor is enough to insulate you from 110V AC?
posted by Nice Guy Mike at 8:25 PM on March 31, 2008

I don't have anything to add, other than to say Ryaske's answer(s) should be ignored. I have been known to replace power outlets (110V only) without shutting off the circuit first (sometimes I need that light on...) Without taking extraordinary precautions, in the average home you're going to get shocked if you touch the wrong piece of metal.
posted by pmbuko at 8:44 PM on March 31, 2008

I have been (mildly) shocked by a live wire while wearing rubber-soled shoes on wooden stairs. Please ignore Ryaske's answer.
posted by maxwelton at 9:54 PM on March 31, 2008

I certainly have been, not fun.
posted by whoaali at 10:11 PM on March 31, 2008

I feel obligated to pile onto Ryaske here too. Raises a valid point, but for practical purposes you should start with Patapsco Mike's answer.

You can visualize voltage as something like the pressure in a pipe. So imagine you've got these two pipes running into your home, full of hydraulic fluid. Far away, at the power station, those pipes are connected to pistons that move opposite to one another: One moves in and the other moves out, then they reverse. So the pipes enter your house, and as the fluid flows back and forth it drives little waterwheels that power your appliances.

With me so far? Great. Now, the deal is, there are a few things in your house that need the full force that that water can provide. Things like washers and driers, electric ranges, that kind of thing. You have probably seen their wonky-looking outlets and plugs once or twice—they are not like the regular appliance plugs. This is for a reason: Regular appliances don't generally need that much juice. So what we do is, we plumb each of your regular sockets with only one of the pipes from the power station, and with one pipe that just goes to a big pool somewhere. The waterwheels still spin, but they're only being driven from one side, so they only receive half the force.

This is what everyone is talking about with the words 'hot/live' vs 'neutral'. At the hardware store you can get a little circuit tester that looks kind of like a screwdriver: If you stick it in the hot side of the socket, it'll light up, but if you stick it in the neutral side, nothing. This is a handy thing to have before even thinking about addressing electrical problems in your house, and by handy I mean mandatory. Newfangled ones even have the tip all wrapped in plastic, so you can feel much less weird about grabbing them and sticking them in a live outlet than I did when I learned to use my dad's old-school one. But the old-school one had the virtue of being entirely passive—no batteries to change, just a little light and a hefty resistor and a metal clip you had to touch so it could take advantage of your body's capacitance to pass a minuscule AC through. Sigh. Yer modern magical measurement-at-a-distance just doesn't have the cachet.

Now, that's two prongs. You are probably wondering where the third prong comes from. Well, our imaginary hydraulic system is designed not to leak everywhere. Every socket also has just a plain old drain connection, so that if the fluid happens to spill inside your appliance, it can be drained out harmlessly. In electricity this is called 'ground'. In the event that a wire busts loose inside your vacuum cleaner and hits the metal chassis thereof, the chassis becomes electrified, which is bad if you're holding it to vacuum with. The ground connection connects that chassis to something big, ideally a metal pipe that goes into the earth, that can take a lot of current. This in turn should cause your fuse to melt or breaker to trip. That is the third prong of a plug.

Now, electricity is pretty darned good at finding its way around. Better than hydraulic fluid is. If you put a stopper into a pipe and you don't wedge it in well, you may find a leak. In electrical terms, this is having low resistance. High resistance makes good insulators, and low resistance poor ones. Now, if that's resistance, and voltage was the pressure of the water, current is the total quantity of water that passes in a given amount of time. These three are related by Ohm's Law: Current in Amperes equals Voltage in Volts over Resistance in Ohms. This is about to become very important because current is actually what kills you whenif you screw up with electricity.

The resistance of air is darned good, which is why your sockets don't sit around sparking when there's no plug in, and why Ryaske's voltmeter with one lead dangling in open air doesn't show much: Air is mostly empty space, with only a smattering of molecules kicking around in it. Imagine a dead-end pipe with a cap on it: No current flows inside. However, the resistance of your body, shoes, carpet, house, etc. is not very high, and you are in very solid physical contact with them, unlike the voltmeter. Imagine that cap has a slight hole in it. If the pressure behind it were mild, not too much would leak through, but the pressure behind it is not very mild at all. Which leads to the vitally important point:

You are a viable medium for both pressure waves and electricity. You are that leaky cap. So obviously, if you get yourself between two of these pipes, it is going to drive you back and forth. If the body part that it drives, in its forceful and unnatural rhythm, is your heart, you're in trouble. This is why you will see wise people working with electricity with one hand in a pocket: You might get a current up your arm and down your leg, but you might not get it straight through your chest. And it only takes about 30 milliamps across your heart to send you to the great breaker box in the sky.

But! It turns out you're not just a pipe, either. You're also a bit of a pool, so even if you're only connected to one of those pipes, it'll kind of pulse into you, and the wave will reflect off the far side of you, and then back into the pipe it came from. In electrical terms, this is called capacitance, and it is the major reason I would not go touching the live wire even if I were perfectly insulated from everything else, as per Ryaske's suggestion. I'm not sure what kind of internal currents it might set up, even briefly, between the various capacitances of my organs. (Wall voltage can produce the fatal 30 mA current even through 4000ish Ohms of resistance, if I've got my sums right. I'm pretty sure no/few human organs actually have the capacitance to charge up to wall voltage, but ... I'm also pretty sure that certain stretches of my moist tissue have less than 4kOhms of resistance to them.)

Incidentally, high-voltage transmission lines are serious trouble to power down. So they don't power them down for routine maintenance. Instead, they send a dude up in an extremely well-insulated cherry-picker. He has a rubber rod impregnated with a small amount of graphite, which he grabs onto and lays across the line. Its resistance is huge, and calibrated so that the huge voltage of the line divided by the even huger resistance of the rod makes a tiny, tiny current, which gradually charges the lineman up to the potential of the line. Then he's free to do whatever to it. Before he can touch the rest of the world, though, he's got to come down to the same potential we're at, slowly, by dropping the same rod on a ground and slowly, slowly discharging what he's got in him. If he just came down and hopped out, the current from him to ground would be brief but too high, and it would be CPR city from there. But as long as they take the change slowly, it's fine. These linemen work in essentially the circumstance that Ryaske hypothesizes. Anecdotally, they also develop extremely white hair in their thirties.
posted by eritain at 11:07 PM on March 31, 2008 [3 favorites]

Well, there's plenty of good theory being posted. But the difference between theory and reality is that there is no difference. So I decided it was time for a practical approach.
No I'm not sticking my finger in there - I took a measurement! :-)

Plugging one probe of a multimeter into the socket while the other probe is unconnected, yields 14V AC. But connecting the unconnected probe to one lead of an unconnected capacitor (to more accurately simulate there being a person connecting to the socket) raises the voltage to about 16V. Unfortunately I don't have any human-sized capacitors, this was just a tiny one, smaller than the tip of my finger.
I think something as massive and wet-on-inside as a person would incur a much higher voltage. I wasn't going to touch it myself, so I created a mini-me that was wet-on-the-inside by filling a glass with water and putting the unconnected probe in the water. (I was handsomer than my mini-me, but mini-me tasted better).
The glass of water raised the voltage to 22V. I'm equivalent in mass to about 140 glasses of water, and extrapolating from that, I'd probably get a noticeable belt if I touched a prong. (From memory, a shock starts to be noticeable above 30V)


If anybody REALLY wants to try something that is literally hands-on, a DC wall adaptor will produce say, +9V relative to it's negative, but if it's a particularly cheap and crappy adaptor, that negative can be oscillating and floating relative to ground, due to the AC source of the power. The positive is always 9V above it, but who knows where the negative is relative to ground - and relative to you. If the negative reads about 50V AC or more relative to earth (use a multimeter), you suddenly have a safe painless way to discover that you can indeed get buzzed by only touching one wire. In these cases, run a finger over the negative of the 9V output, and you can feel it like a slight vibration at the point of contact - even though you are insulated and don't form a circuit.
I imagine that if you replaced that low-power 9V wall-adaptor supply and it's crappy negative floating at about 50V AC, with full-on mains-power at mains voltage, you could get a decent belt without completing a circuit.
posted by -harlequin- at 12:32 AM on April 1, 2008 [2 favorites]

But the difference between theory and reality is that in theory there is no difference.

FTFM.
posted by -harlequin- at 12:36 AM on April 1, 2008

I've read most of these, and some are misleading.

In US AC distribution (120V nominal), one prong is HOT, one NEUTRAL, and one GROUND, in a three prong socket. (Not all sockets are three pronged. Two pronged sockets have no ground, just HOT and NEUTRAL.)

If YOU touch the HOT prong (the narrower of the two), a current will flow from where you touch that prong and any point with a lower potential that you are also touching. That can be either GROUND, NEUTRAL, or some other point that's in between. The amount of current will be proportional to the resistance applied between the points.

If you were to move your finger to the NEUTRAL prong, you'd get a much smaller (probably imperceptible) shock or none at all, because ideally, neutral is very close to ground. How far away from ground it is is proportional to the amout of current flowing in that neutral lead at that time, and its electrical distance from the point at which the NEUTRAL and GROUND leads connect, way back at the electrical distribution box where power comes into your house. The voltage is propotional to the wire guage and material, and is related to its DC resistance, and to a lesser degree, it's reactance.

If you touch only the GROUND, you shouldn't get shocked unless you are unknowingly touching something else that has a higher potential than the ground...

To get shocked, current has to flow. Current will only flow when a potential is applied across a resistance. A potential (i.e., voltage) only exists between two points. If you are only connected to one point, you have no potential applied and you won't get shocked. (I'd sit all day on a dry wooden stool with a HOT wire in my MOUTH, safely.)

(For the persnickety, these observations are for normal voltages. The rules change a little for super high voltages than can exceed the dialectric strength of any materials insulating you from a lower potential.)

To be percieved as a shock, the current has to rise to a threshold... you are unlikely to feel a few microamps, but you will likely feel a few milliamps.

So the OP's question is answered best... it depends. There are several scenarios, some of which could result in a shock. Some shock pathways can be lethal, others alarming.

I'm not recommending that you do this, because wiring mistakes are known to happen and do, but generally, if you touch the wide prong or ground, only, you won't get shocked. If you touch the narrower prong, you may, but probably won't, depending on what else you are touching.

(IAAEE.)
posted by FauxScot at 5:18 AM on April 1, 2008

brain... hurting...

let's just say i'm not gonna touch a plug, and i'll make sure that all my plugs are firmly inserted all the way. ;-)

thanks, askmefi!
posted by cgs at 9:04 AM on April 1, 2008

ok so there is definitely more knowledge here than I had .. so I digress. I did totally disregard capacitance in my theory!

but still ... as I've said .. I have seen a human being touch just one leg of hot AC current and he did not even flinch while holding his hand there .. and he has done it multiple times.

So ... at least in his specific conditions , there was not enough voltage to kill him or even feel a tingle.

And again ... you are completely stupid if you try this in any way shape or form. Especially because of knowledge given to you by complete strangers over the internet. So if you are still dumb enough to try it .. you deserve whatever may (or may not) happen to you.

Great knowledge shared by all , thank you !
posted by Ryaske at 10:41 AM on April 1, 2008

ARGH!! This thread..

Some people incorrectly state that electrocution is caused by voltage, it is not. Electrocution is caused by current flow. Voltage is the push that causes current to flow, but it is the current that does damage and causes pain.

Also, the capacitance argument is ridiculous. A capacitor with a floating terminal can't charge, so no current flows. It sounds like eritain is trying to think of a human as some kind of transmission line.. The relevance of that kind of interpretation here is just about zero, because the wavelength at 60Hz is about 5,000 km.

Perhaps the confusion is related to static electricity, but that would be a misunderstanding. For one thing, when you get a static shock you aren't feeling the current flow, you are feeling the local heating caused by current flow. Consider the common notion that you can use a piece of metal in your hand to discharge yourself pain free. The current flow is far below the threshold of detection, even though you are being discharged from voltages many times higher than mains voltage.
posted by Chuckles at 1:10 PM on April 2, 2008

The absolute answers here are wrong. You will not always feel an electric shock if you touch, and only touch, the hot wire of typical US home wiring; and you will sometimes feel an electric shock if you touch, and only touch, the hot wire of typical US home wiring. As people state above, it all depends upon the available path to ground through you, and that can vary quite a bit. It can vary by your body, by what you're wearing, by what the materials your flooring or similar is made of, and by how humid it is.

Basically, don't count on not being electrocuted unless you know with certainty you're not grounded; and even then don't think you're certain unless you're competent to make that judgment. Meaning, you're probably not, so don't.

Some other things. As Chuckles says, for the purposes of this discussion, what's important is current and not voltage. Lots of electricity flowing through things, like the tissues of your body, causes various damage. Primarily heating due to resistance; but other things, too. Brief flows of current from home 120V US wiring don't cause that much of this type of damage so that's why you can occasionally get a quick shock and be unharmed.

However, your primary fear with home AC current should be twofold:

First, any sort of situation where there's a possibility you might sustain a shock for more than a moment is dangerous. This danger can be subtle: some of the worst shocks I've had have been from any sort of delay in a triggered current¹—when you get a shock by brushing up against a live current, you're (generally speaking) likely to react and pull away from it. But if you have an opportunity to hold onto to something and then the current flows, your reflexes are different and you'll likely sustain the current for longer.

Second, the real health risk of home AC current is the current flowing through your chest and around your heart. Muscles contract from electric current (which is why, in the case of the previous paragraph, you can be forced by the electricity to grip something that's shorting you to ground) but AC means alternating current, going one direction and then the other and switching 60 times a second in the US, and that's in the range that is likely to confuse the nerves that are controlling your heartbeat, sending it into arhythmia or stopping it altogether. Any chance of even a moderate AC current going across your torso is a serious health risk where there's a possibility of death.

The most dangerous sources of electrocution aside from home AC-caused heart attacks and stoppage are the very, very high currents discharged by various capacitors used in electric/electronic equipment found commonly in everyday life. These are almost always shielded from easy consumer contact—but if you get into things, they're there. They're particularly dangerous to the unwary because capacitors don't have to be connected to an external power source to be deadly. Capacitors are like quickly charging and discharging batteries. Well, not "like", but "are". That's what they're used for (and to even out the flow). Capacitors in electronic equipment are not discharged when the device is turned off or even unplugged. They can be fully charged, and they can push a huge amount of current through you to ground in a very short time. They can kill. There is a large and deadly capacitor in your car's engine compartment used for generating the current that sparks your engine...stay away from it. There are huge capacitors inside your tube television. Stay out of the inside of your TV. Many sorts of large power supply transformers, like your computer's power supply, have large and deadly capacitors. That's why your computer power supply is itself enclosed in a box that you should stay out of.

1. I'm very nervous around telephone lines from all the times I was shocked as a youth. Your phone line "turns on" when the phone company detects that the two lines have been connected for more than something like half-a second. Then they send aprox 70V DC, with a not-insignificant current. It's not really dangerous. But it's enough to give you a good jolt, and, more to the point, you've likely gotten a nice good grip on those two wires. I really am more nervous—not for safety reasons, just conditioning reasons—when handling live phone wires than home wiring.
posted by Dances with Werewolves at 8:31 PM on April 15, 2008 [1 favorite]