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Toddler in Critical Condition After iPod Cable Shock
- Thread starter patrickdunn
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This isn't correct. You wouldn't be able to operate anything plugged into it if that were the case.
Firstly, I hope she makes a full recovery.
I used to be a paramedic (with a bachelor of health sciences (paramedic stream)) so I'll shed some light on this issue.
The voltage required to reset the heart (intracellular) is very low.
We're talking less than 100mV and a less than 1mA.
see:
http://en.wikipedia.org/wiki/Action_potential
http://en.wikipedia.org/wiki/Resting_potential
http://en.wikipedia.org/wiki/Cardiac_action_potential
The human body is a big sack of salty fluid. Internal conduction is very good. It is not beyond reason to believe that a 5 volt 1amp source (it was an Apple USB adaptor right - and they are 5 watt) could cause fibrillations (or defibrillate, depending on how it happened) in your heart. Unlikely but not impossible. It would have to discharge through the heart, again unlikely since 5v is not enough to earth out of your skin, but not impossible. A young heart should kick back in though - once the power source is removed.
External conduction is a different kettle of fish. The skin is a pretty good insulator. Look at this next page, it has a chart with resistance of skin.
http://en.wikipedia.org/wiki/Electric_shock
What is more interesting is the burns. How much heat could a 5 watt source generate? (duh, 5 watts worth) Maybe if the power was only delivered to a very small area of the tongue? I don't know. Electrical burns were very rare when I was on the job.
On balance though, I think 120V is the more likely culprit.
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Very true, but sadly we live in an age where someone else is always to blame. A large section of society would now need to look up the words "personal responsibility" in a dictionary. When my children were young we had devices all over to prevent accidents e.g. safety rings on the cooker so they couldn't pull a saucepan down on themselves, blanks plugged into each vacant electrical socket etc. etc. oh and I had to grow an extra pair of eyes in the back of my head and forgo sleep - for years.
Do you guys know how landed into this forum today? I just google to see if iPhone / USB cable can cause electric shock. Thats why I am here.
5 minutes ago, i received a shock from my iPhone connected to my iMac with the USB cable. It is unbelievable, but true. For the past few days, I have been feeling static on my iMac and today even when the iMac was off, the USB cable was receiving the power. I am not sure about the voltage though.
I quickly grabbed a tester and touched the iPhone surface and believe me it is glowing.
I shutdown everything, checked the cable and reconnected everything. Now things seems to be ok, but I am scared like hell.
It seems I have to call the service guy ASAP. But I will be looking like a stupid unable to reproduce this in front of him.
I get a "shock" like this if I touch my USB keyboard on my PC and the case of my MacBook at the same time. I'm pretty sure it is due to a slight difference in the ground voltage on the two devices. Nothing to worry about.
I actually think it is possible... The shock could have been strong enough to triggered something that injured the toddler.
Looks like you have a Hazardous grounding problem.
I'd highly recommend getting that fixed.
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.005 A is correct.
Its differential current. If the current going out is different than the current coming back by 0.005 A then its supposed to trip.
If the current that goes out is not the same as what is coming back, then there is a leak in the system. And likely hazardous.
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No.
The problem was a nearby lamp was faulty and had 120V at the surface. The child's shoulder was burned. The current went through the lamp, through the child's shoulder through the ground USB cable.
No, it isn't correct.
The post to which I replied says that the circuit trips at 0.005 A, not a differential of 0.005 A.
A kitchen appliance won't run on a current of 0.005 A.
It's like saying I'm 9 inches tall when in fact I'm 9 inches taller than my wife.
USB can carry enough current to cause injury.
USB carries something like .5 amp or 500 milliamp.
Low voltage but enough amps
Your reading on your meter is set to resistance. The earth ground on your home and the chassis ground of the iPad could have 150 ohms of resistance. The chassis of the iPad is connected to your home outlet via a USB charger which carries a signal ground, so it is possible to have some resistance because earth and signal grounds are isolated. If you had 150V difference of potential, then I would be a little more worried.
Thoughts and prayers are with this poor child to make a full recovery. Nothing saddens me more than children suffering.
As posted before, only when you disregard the laws of physics.
Current = Volt / Resistance.
USB only carries 0.5 Ampere when the resistance is 10 Ohms or less. The human body has a resistance of 1000 Ohms under worst conditions; usually it is a lot more. Therefore the 5 Volt of USB will only result in a current of 0.005 Ampere under worst circumstances.
I live in the US and don't know how your AC mains are wired but it looks like there is a problem with your outlet. Either that or you are measuring the wrong conductor.
If the case really did have 150+ volts on it relative to ground you could not touch it.
It's on the V100 selector, so it's about 1.503V going through it.
I've actually tested this at work and at someone else's house - no changes there.
FYI, I think the newest Apple USB adaptors for iPad carry up to 2 amps - after all they are 10 watts.
Remember that the external human body has high resistance - internal has very low resistance (hence the magic battery life of pacemakers which only need to deal with extremely low currents and voltages).
Did you take any physics at school at all? The voltage is the same. Since the same person would be touching it, the resistance is the same. Therefore the current and the damage is the same. Touching a 10 Watt USB adapter or a 2.5 one doesn't make one bit of difference.
The iPad has lower internal resistance - very easily calculated; 5 Volt and 2 Ampere means the resistance must be 2.5 Ohm (5 divided by 2). With an old 2.5 Watt adapter, attaching something with 2.5 Ohm resistance would just result in the voltage dropping down.
And when you comment on the "internal resistance" of the human body: Well, I wouldn't recommend implanting a USB connector close to your heart and then switching the power on. But 5 Volt applied externally are completely safe. The iPod USB cable in question wasn't connected to a 5 Volt USB port on a Mac or PC or a USB charger, but to 120 Volt produced by faulty wiring. So 24 times more voltage, 24 times more current (same resistance and a power supply handling any demands easily), for 576 times more damage than a USB cable properly connected to a Mac.
Yes they do trip at very low current. But that is ground fault current. The device compares the current out one side and in the other and if they differ by 0.005 amps the power is shut off. The assumption is that if they differ there is a path to ground, like through a person.
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Yes. That is reasonable and normal. It is common to have the neutral about 1.5 volts above ground. It is more common to see this in a larger building but it could happen in a house if you have a lot of stuff running on the branch circuit. The 1.5V is cause by voltage drop along the wire in the branch circuit.
This is an interesting experiment. It does show that you can measure a voltage differential, but it does not give an explanation of why or if it has any ill effects.
The first test I would do is to check the Usb wall wart for manufacture markings. There are people out there not really taking proper care when manufacturing things. Wall wart power can be dangerous and things manufactured the wrong way can cause harm. A usb wall wart should be double insulated, the sign is a double square. It should also be tested by something like UL. The testing for security includes things you cannot easily measure yourself without destroying the wall wart. I am not sure but, is it an Apple wall wart?
Secondly, this voltage is probably totally normal. My bet is that if you change to measuring to Ampere instead, you will not be able to measure any current at all. The voltage you measure is possibly induced and carries very little power. And the voltage measurement instrument is designed with a very high impedance input in order to not influence the measurement. Not beeing able to measure any current is a sign of a high impedance source which makes the voltage you measure non harmful.
Once I was shocked by my iPad's wall plug, and it was definitely a surprise, but I was unharmed. I imagine for a toddler, it would cause more damage.
I wonder if the cable was frayed at all, because I would like to think that most cables are pretty contained.
I wonder if the cable was frayed at all, because I would like to think that most cables are pretty contained.
You should read the article. No wall plug involved. And it had nothing to do with the cable being an iPod or USB cable. These people had faulty wiring so that some surface in their home was connected directly to 120 Volt, and when you have that, things tend to go wrong in very dangerous ways.
Yes, at university level. Of course the voltage is the same. That's why I said it was 2 amp from 10 watts (being 5V x 2A). USB is by definition 5V - and it could of course deliver an arbitrary amount of current (although the USB 2.0 specification does seem to top out at 1.8A).
Funnily enough there is a Powered USB version. It can deliver 24V @ 6A = 144W = enough to kill you. http://en.wikipedia.org/wiki/Powered_USB
I happen to be a paramedic (Bachelor of Health Science). Did you take any medical training anywhere? I can gladly tell you that skin resistance is not the same for any two different people. These differences occur from different gene expressions for skin. It also differs for different parts of the body and it differs by age (for the same person). So you can't treat skin resistance as a constant for different people. And as above it even differs for a single person.
I'm very glad you wouldn't recommend it. I wrote several posts back that it was likely to be 120V. You don't need to tell me how much more dangerous higher voltages are. The damage doesn't work out like you've shown. It's a function of several factors (skin resistance, internal resistance, body part contacted, path through body, time in contact with electricity, etc.). So you can't put a damage factor to it.
Ask a sparky how many times they've been hit with 120V or 240V and you'll be surprised at how many walk away with zero damage after substantial shocks. It's not a cut and dry thing.
Unfortunately (or fortunately for anyone), the iPhone uses a USB 2 slot, which according to your link provides only 2.5W. This is all moot anyway, as it was because of faulty housing in the house in general.