Will a laptop power connector kill you if you put the end in your mouth?

April 11, 2007 10:04 AM

How dangerous is the business end of a Macbook MagSafe laptop power cable to a small child?

Do laptop power cables have any sort of circuitry to prevent them from shocking you? The Macbook mag cables are pretty easy to pull out, and about the right size for a small child to decide that this should go in their mouth. Obviously, these should not just be left lying around where babies are playing, but when using a computer near a baby, there's always a danger that they'll reach out and grab something before you can stop them. The MagSafe connectors seem like a bit more risk because of the relatively little effort it takes to disconnect them.

How bad would this be? A mild shock? Fatal? I've never heard of a single case like this.

I already called Apple tech support. They couldn't answer the question and referred me to my local Apple authorized support dealer, who I don't really consider an authority on child safety. As you might expect, I'm somewhat reluctant to experiment.

posted by Caviar to computers & internet (25 comments total)

I just put one on my tongue and got a mild shock. I really had to get the whole surface in contact with my tongue to get an effect. Of course, I didn't leave it there too long -- hopefully the baby would do the same. (The things I do for AskMetaFilter!)
posted by jjg at 10:17 AM on April 11, 2007 [58 favorites]

jjg - ?!

You are a daring human being.
posted by voidcontext at 10:18 AM on April 11, 2007 [1 favorite]

It was a very mild shock, like licking a 9-volt battery. Just a tingle.
posted by jjg at 10:21 AM on April 11, 2007

Well, these folks are selling a Magstay (?).
posted by R. Mutt at 10:26 AM on April 11, 2007

I've done this before, accidentally...trying to do a couple of different things at once, holding the laptop-plugging it in-juggling folders...and ended up with the laptop plug between my teeth since I was out of hands. I touched it with my tongue and got a little shock...no big deal.
posted by Liosliath at 11:09 AM on April 11, 2007

It is almost completely safe. The output is transformer isolated (no current path between you and wall outlets), and the voltage is low (not enough voltage to push a harmful current through your body) - wikipedia on Seperated Extra Low Voltage, for more details.

Also, the best previous questions I can recall on electrocution: Electrocution in a pool. It has lots of helpful discussion and links.
posted by Chuckles at 11:15 AM on April 11, 2007

It seems reasonable to discourage small children from playing with power cords in general even if that particular power cord is not very dangerous.
posted by aubilenon at 11:16 AM on April 11, 2007

Also, the Magsafe connector contains an earth ground pin. This would mean that the current would flow only across a few milimeters of your tongue, rather than across your body and through vital organs, e.g. your heart. With the 85 watt adapter used by the MacBook Pro, the MagSafe connector is putting out about 12.4 amps at 6.86 volts. This seems pretty minimal to me, but someone with a better understanding of the effects of various currents on the human body would be better qualified to comment on what this could do to a small child.

I am not an electrical engineer, and while I admire jjg's courage (and his book!, which for the record, I got purchased by the University Library), I'll avoid trying this for myself.
posted by zachlipton at 11:17 AM on April 11, 2007

the Magsafe connector contains an earth ground pin

That really isn't an improvement. If you are grounded, you can be electrocuted by touching something with a fault. If you are floating, it takes at least two faults. Check the wikipedia page, it is the difference between Separated Extra Low Voltage and Protected Extra Low Voltage.
posted by Chuckles at 11:24 AM on April 11, 2007

If you are floating, it takes at least two faults.
posted by Chuckles at 11:25 AM on April 11, 2007

While jjg went and took one for the team, I can attest to the fact that they are fairly safe, as I came home last night to find one of my cats gnawing on the magsafe adapter. He's not dead, and appears no more stupid than before. He WAS purring, though.
posted by Cat Pie Hurts at 11:48 AM on April 11, 2007 [3 favorites]

jjg is awesome.
posted by humblepigeon at 12:22 PM on April 11, 2007

aubilenon writes "It seems reasonable to discourage small children from playing with power cords in general even if that particular power cord is not very dangerous."

Note: he refers to her many times as "baby". My kid, at 8 months, was still a baby, was old enough to pull out plugs, but still young enough that sometimes he thought "No!" shouted with a stern face and deep voice meant "Daddy is playing a game", and giggled. Teaching kids is easy. Teaching babies is hard.
posted by bugbread at 12:26 PM on April 11, 2007

Holy crap. Did someone really just stick something that could potentially have killed them in their mouth, to answer a question on Ask Mefi?

Wow.


Just, wow.
posted by Happy Dave at 12:45 PM on April 11, 2007

We used to do this in college. It was a fun party trick, something like "It hurts if you put it on your tongue". I can't speak to the voltage or child safety, but like our Stuntman jjg, I can vouch that for an adult (Or a stupid college student) it's little more than a curiosity.
posted by GilloD at 2:23 PM on April 11, 2007

Holy crap. Did someone really just stick something that could potentially have killed them in their mouth, to answer a question on Ask Mefi?

no. seven volts has no potential to kill you. are people really this ignorant about the technology they worship?
posted by quonsar at 2:44 PM on April 11, 2007

no. seven volts has no potential to kill you. are people really this ignorant about the technology they worship?

Actually, seven volts is plenty to kill you, should the line also carry 3000 amps.

Not that I'm saying that was the case here, before you give me a lecture on AC/DC transformers.

The awe we have in jjg is that he danced with the danger of tongue-shock, not death. He also risked destroying the power adapter for his MacBook, and they're quite costly to replace.

And I've personally never worshipped technology, although my local priest has been seen wearing an iPod.
posted by humblepigeon at 2:50 PM on April 11, 2007

We used to do this in college. It was a fun party trick, something like "It hurts if you put it on your tongue". I can't speak to the voltage or child safety, but like our Stuntman jjg, I can vouch that for an adult (Or a stupid college student) it's little more than a curiosity.

Reminds me of a friend I had at school. After we'd been taught about how AC/DC transformers worked, he took an old power block from his home computer and turned it into a neat weapon.

He reversed the transformer, so that it stepped-up. In other words, he connected a battery to the end that normally plugged into a socket. He also cut the end that normally connected to the computer so that it was bare wires.

He then spun the bare wires around his head and then threw them at people. When they came into contact with skin, it gave a pretty nasty shock.

Did I mention that he was also mostly blind, so couldn't even see where he was throwing the wire at?

Happy days.
posted by humblepigeon at 2:58 PM on April 11, 2007

My dad used to have me and my brother lick the business end of a 9V battery every once in a while (Dad would go first), and said that power cords were about the same.

And even though the baby in question is still a baby, I agree with aubilenon that discouragement is best because a baby doesn't have the ability to distinguish between 110 V and 220 V. If the baby's old enough to put the item in his or her mouth intentionally, s/he's old enough to start getting trained. The key is to not yell, but to simply withdraw the item with no fuss and redirect.
posted by cocoagirl at 3:05 PM on April 11, 2007

no. seven volts has no potential to kill you. are people really this ignorant about the technology they worship?

All snark aside, here in the UK, we have 230 volt plugs. And I, personally, don't know enough about power, or power converters, to want to try sticking anything electrical in my mouth. Regardless of what people on the internet tell me.

Props to jjg for having the knowledge (or bravery, if he didn't have the knowledge) to do it. Unlike you, I didn't assume that he would have that knowledge. Because I don't. And neither, by the way, does the OP.
posted by Happy Dave at 3:47 PM on April 11, 2007

Meh, it's 7V. If anything, bringing kids up is about controlled-accidents, some place they can learn to fall, and the pain that comes with that, but has as little chance as possible of serious injury. With 7V, have at it, the kid should learn to respect electricity soon enough.

Standard disclaimer goes here!
posted by lundman at 6:28 PM on April 11, 2007

I just tried licking my iBook's connector. Unfortunately the outside sheathing makes it rather difficult to get the tip of my tongue down to where the power is.

It claims to be providing 0.24V @ 2.7A. The voltage number seems bizarre. I should think it's more likely 24V.
posted by five fresh fish at 7:13 PM on April 11, 2007

I bit down on my iBook cord while it was plugged in once (on accident!). It gave me a bit of a jolt (no other way to describe it-- it felt like shock waves traveling out from my teeth and through my head) but it wasn't all that painful. And as far as I know, it caused no lasting damage.
posted by chickletworks at 11:10 PM on April 11, 2007

I just tried licking an active power line but it tasted pretty much like a wooden pole.
posted by sparrows at 12:01 AM on April 12, 2007

7V is plenty enough to kill you if it doesn't have to go through your skin and you manage to get 10mA or more via the heart - the 10mA (maybe 30mA if you're fit) through the heart is about all that matters, unless you're talking about enough power to cook someone. Skin has high resistance (50k-200k) so 7V will get you about 70uA between fingertips.

Connect one side to your tongue and the other to a cut in your arm however, and there's mostly just saltwater in the way (blood) and that conducts very very well. Fatally well. Even an AA cell could be fatal in this way if you're clumsy and/or determined enough and they're only 1.2-1.5V.

Of course, that's difficult to do with a laptop plug or 9V battery since the contacts are close together and most of the current will take the shortest path.

fff: it's 24V. 19V and 24V are both pretty common for laptop supplies.
posted by polyglot at 4:58 AM on April 13, 2007