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Laptop + bath = death?

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Letters Oh boy - the letters on the Creative advert just keep coming. For those just joining us, this is the debate over the question of whether you could drop a laptop (battery-powered) into a bath occupied by a person without killing said person.

The only conclusion it is safe to draw from all the various explanations is that (short of testing the idea by dropping a laptop into the bath of a volunteer), we'll never know if it is safe to do, or not.

Anyway, a selction of the various view points are below, and we'll call this the final word on the matter, shall we?

To all who wrote in concerning the laptop in the batch, all I can say is that I hope you're in software or perhaps banking, because you know little about electricity!

To all those who wrote that "it's not the voltage, it's the current", noted. To all those who wrote "it only takes 100 micro-amps to disrupt a human heart", noted. To all those who pointed out the potential voltage and current that a laptop display uses even on battery, noted.

My question to you is: how does one place ones body, with a path including the heart, within the display circuit? You must disassemble the case, disconnect a lead, and use opposing hands to complete the circuit to achieve the predicted results.

Otherwise, while you're body is indeed grounded, the laptop display has it's own INTERNAL ground, and is completely unaffected by the ground you proffer.

Now, if the laptop IS plugged into the mains, all bets are off, of course.

-- Danny


Subject: Creative ad bath shocker

"It's not the voltage that kills you, it's the amps. Low voltage is USUALLY safe because it does not have enough oomph to jump from a dry wire to dry skin. But soaking in water changes that. 10 volts from a laptop can easily kill you dead in that situation."

Rubbish - stick your (wet) tongue across the terminals of a 9v battery, instant death or just a tingle?

"And a stun gun is a "battery powered" device that can kill you."

that's because you stick two electrodes into the chest and deliver 10,000 volts across the heart

I'd agree with Creative, it's not dangerous on battery power In order to kill you , the current must travel through you, since the laptop is just sitting in the bath (after you'd dropped it in), it would just short out, not travel through you. Even if it was live and you touched earth (say the tap) there's no circuit, so no smoke.

Mains supplies in UK bathrooms are isolated, so even if you drop your mains shaver in the bath, it won't kill you.

So you'd have to hold on to the tap, and drop in the transformer plugged into an extension lead from your hallway.

Paul Nicklin


Hi Lucy

I'm afraid I have to disagree with your other readers letters Ian Smith and Mike.

Whilst they are correct that it is current which kills they still miss the point that a certain voltage across the human body - in the right place is neccessary to drive the required current through the heart. To my knowledge the lowest voltage that has ever killed a person is 36v. I can happily grab both terminals of a car battery (fully capable of driving a few hundred amps through a car's starter motor) with wet hands and suffer no ill effects (lead poisoning from the terminals not withstanding), the voltage is simply not high enough to drive the current required to stop my heart through my body. I don't reccommend doing this with a running car as the ignition (at several hundred KV) is certainly capable of killing.

Provided we're talking about battery powered laptops (Ian's point about mains powered laptops with internal transformers being perfectly valid - jump in the bath with one of these plugged in and you're dead) I firmly believe you're in no danger (aside from the cost of a new laptop). The battery will a). not drive enough current to kill you and b) it will just drive current around the battery, electrolising the water near it. When mains kills in a bath (toasters being popular) the electricty is trying to short out between live and ground. The most convenient ground point is the pipe connected to the bath plug so the current takes the course of least resistance

If there are HT circuits inside to run displays, these will short out in the water, they simply don't have enough power to drive the required current though the body.

As for ratings at 2500 volts, thats a test rating for static resistance, not the voltage it runs at - do you seriously think laptops have 2.5Kv inside them?!?

Anyone has a laptop they don't like I'll supply the bath.

The add was irresponsible since it might encourage people to do something silly, like plug in their laptop because its battery was low and I agree with that conclusion.

Surely there being a problem with using battery-powered laptops in the bath would also preclude their use outside, as many ads portray, as anyone being caught in a sharp downpour would be at risk. The lack of serious incidents, or indeed such ads not being savaged by watchdogs, would seem to imply that this is not much of a problem.

Roger


In a modern house (at least on the NA side of the pond) it would be SAFER to throw a plugged-in desktop computer into the bath. The electrical code requires that outlets in the bathroom by protected by a ground-fault interrupter (GFI). The GFI senses when current starts to leak to ground (when it is still at the microamp level) and within a millisecond or so cuts off power to the outlet. This is fast enough to save your life if a radio or a desktop computer falls into the tub. But a laptop, even if it was plugged in, would just react to the mains cutoff by switching to its internal battery. Result: fricaseed consumer a la Thinkpad. But hey, they call themselves "Creative Labs", not "Smart Labs" or "Well-Informed Labs". -- Gord Deinstadt

My laptop battery says “li-ion” - lithium….

…hmmm, last time I dropped a couple of grams of lithium into water it was a very pretty fireworks display.

I wonder what happens when you drop a kilo block of the stuff in…

Dom

Our guess is that a kilo of lithium would go BOOM! (And it would be cool to find out. From a distance anyway.) But we suspect the Li in a laptop battery is safely tucked away from water, one way or another. See remarks about rain showers above, and consider the frequency with which coffee/cola is spilled on keyboards.

So it won't kill you. Or it will. Maybe. OK, Let's move on.


Researchers at Stanford discovered an upper limit to hard drive write-speeds. Although they claim it is some way off, others wonder if that is so:

Hi Luce - Enjoyed your article on this, as ever (I always know it's one of yours if it mentions 'Boffins') but was wondering if we're closer to the limits that you suggest. I get plenty of gobbledegook on my hard drive - but then maybe it's faster than I thought...

James Pickett

Such a good word, gobbledegook. Resolve to use it at least once today!


This week also saw IT professionalism get a bit of a slapping from the Royal Academy of Engineering. Unsurprisingly, not all of you appreciated their conclusions:

In a word, 'bullsh*t'. The danger of pseudoscience promoted in this fashion is that it appeals to people who've bullsh*t their way to the top...we call 'em 'PHBs'. Given another ten years or so, we should have winnowed the know-nothings and least of academically trained dipsh*ts back into sales jobs at PC World, and hopefully stop a secretary in local government handing over a spec for a website that resembles a child's shopping list. Until then the engineers at the thin end of the wedge have to shoulder pap that attacks our 'professionalism' because the guys representing both sides of the customer/supplier relationship talk so much boll*cks they forget that they're a conduit of communication. And if you think that report was aimed at anyone in technical positions...page 14;

'A terabyte is approximately 1,000,000,000,000 bytes. If each byte were equivalent to a letter on a page, 50,000 trees would be needed to make the paper!' Gosh. Not even scientific notation? We're drowning under the opinions of everyone at the moment. If this sh*t isn't peer-reviewed, it's another opinion. I regard it as largely value-free promotion that vaguely waves it's hands in the direction of education while missing the one, most crucial and overriding point about the whole mess. Professionalism is innate.

James


Lastly, and on a lighter note, Micorsoft's new research programme, dedicated to improving human-computer interaction, clearly caused a few amused looks to be exchanged, and probably a couple of raised eyebrows too:

Lucy,

So, Microsoft is going to make computers easier to use? Wow, that makes sense. I hope they use that OS, Bob. It was greatly under-appreciated. Or maybe the ultra intuitive Microsoft cordless phone that could use the software on the computer to match the caller ID with the name of the person in database but not the people in your address book.

Thankfully, the Microsoft of today is all about making computers easier to understand. They are going out of their way by avoiding such naming conventions as Microsoft Windows XP and Microsoft Office XP, then having Microsoft Windows 2000 and then Microsoft Office 2000. Now when a support person calls and says what OS are you running the end-user replies 2000 because Word says 2000 on the XP load they have at home.

Yes, it is about time that Microsoft started using it power for good instead of evil but I won’t hold my breath.

chad


Lucy,

After reading your article "MS to probe human-computer interface" I have to say I breathed a sigh of relief, finally, M$ are going to buy a Mac.

Cheers, -Carl

It was inevitable that someone would mention that, wasn't it? Keep 'em coming. ®

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