Man dies charging iPhone while in the bath
bbc.com
bbc.com
Tragic. Probably cheap USB without mains isolation or maybe enough water dripped down length of cable and socket to create a circuit, because USB is supposed to be 5V DC.
Watch these USB charger teardown horror-shows to further understand why it's rational to pay for proper, authentic CE+UL, high-low isolation and quality components (ie insulated tape in transformers):
If these so-called double insulated two-wire appliances [sans earth connection] such as power packs, various light fittings, etc. etc. were actually fitted with the third earth wire (and appropriately equipped to take it) then the likelihood of electrocution in the circumstances described in the article probably would not have happened.
In most of these two-wire devices the power input is essentially physically symmetrical. If water gets on the active (hot side) rather then the neutral then it's likely to leak by any means to ground (moreover there's no guarantee that active and neutral are correct way around even if so marked (I've seen power sockets active and neutral wired incorrectly quite often but never the earth!). If you are in the way, as they say one flash and you're ash.
Note: it only takes about ~70mA across the chest (i.e.: from one arm to the other) to kill you and that ain't much.
Surrounding the inside of the device with a conductive earth shield that's properly connected to the mains earth via the third earth wire will help because the physically closest point to ground is now the earthed bits.
When water gets inside such an appliance with only a little gap between the active and earth then then it's sufficiently conductive to blow fuses at 240VAC or even the US's 110VAC.
I've examined iPhone type chargers whether Apple's own or third-party ones and frankly they horrify me--all of them! There is precious little physical space between the the hot primary side of the switch mode power supply and the secondary and it doesn't take much water to close the circuit. Moreover, the isolation insulation within these power supplies (the transformers, board insulation etc. is pathetically minimal).
Remember, power systems around the world come with a third earth wire for a very good reason. Power authorities wouldn't go to expense of putting all that extra wiring in buildings, power cables etc. just for nothing. That lesson was learned well over a century ago.
Two-wire 'double-insulated' appliances started to appear about 30/40 years ago. Before that (except in the days of power engineering antiquity 90+ years ago), two-wire circuits were only allowed for certain lights/lightning assemblies.
Oh, BTW, this guy wasn't in a thrived-world country but in the UK. So why wasn't the building he was in have earth leakage breakers in on the switchboard?
Now I need some information that has troubled me for years.
How did these damned dangerous two-wire 'double-insulated' circuits/appliances get approved in the first place? And why did approval authorities allow them to be approved? What was the rationale? Pressure from manufacturers perhaps?
Yes, I've seen the ins and outs of the approval rules and I agree they're perfectly fine when dry--no question about that. But life isn't like that as this poor guy found out. Regulations simply have to assume that water, mains power and idiocy--or even just unfortunate happenstance will all converge at some point.
Finally, I know what it's like to end up nearly dead. Years ago, I got a belt across the chest from an 850VAC transformer rated at 250mA. I was knocked completely across the room 15ft or so and I couldn't move for about 40 minutes . The only reason I survived was that muscle contraction disconnected me from circuit in time. Had my hand been wrapped around the device it would have contracted and I'd have been history.
It wasn't the only shock I've had but it was by far the worst (I was 14 years old at the time and just damn stupid and careless).