OMG, will this thread never end? Watching people who have no clue or just a little knowledge about electricity talk about is makes me want to smack my forehead and hope I go unconscious.
Voltage doesn't matter???? (slap). Nope. I'm not unconscious. All this nonsense about a 3.7V iPhone or 5V iPhone "battery" that charges an iPhone killing someone when it's just running on battery needs to immediately stop. It won't and CANNOT happen.
Time for a little lesson in basic electricity, I guess. Ohm's Law for DC:
Voltage = Current x Resistance.
Dry person skin = about 300k Ohms (300,000 ohms). Wet or broken skin is about 1000 ohms. Internal body resistance = about 300 ohms. Really high voltage can lower even dry skin to 500 ohms in short order.
To
fibrillate or possibly stop a heart (not fry), you need ~500mA of instantaneous current across it (other types of shock that do not go through the heart can be much higher and fibrillation can start MUCH lower (more on that in a moment). But to get that current, you need VOLTAGE. Hence Voltage sure as HELL
DOES matter! If you don't have enough voltage, the current can never reach 500mA.
So forget wet skin for now. Let's go straight to internal body resistance since it's even lower (300 Ohms).
What is the absolute minimum possible voltage is required from a battery to stop a human heart instantly?
V = 500mA x 300Ohms = (0.5 x 300) = 150V
V = 150V
However, the problem here is that 500mA is the instantaneous time and the value changes over time. The real number is considerably lower, particularly for longer term contact and is more like 30-60mA after TWO SECONDS time (which is why a GFCI is a life saving device because it cuts it off much sooner than that!). This is across the heart (the human body can take larger doses of electricity if it doesn't cross the heart, but this is a bath tub scenario so I'll assume the absolute worst theoretical number).
Thus,
V = 30mA x 300Ohms = (0.03 x 300) = 9V
Again, that's internal resistance which would basically mean electrodes would have to be inserted sub-dermal. It's not a real number for a bath tub scenario.
A more realistic number for wet or broken skin is 500 to 1500 Ohms which gives:
V = 30mA x 500Ohms = (0.03 x 500 or 1000) = 15V to 45V
Dry skin is more typically in the 100,000 to 300,000 Ohms or anywhere from 30V - 3000V, although that would quickly drop to 500 Ohms with high voltages as the skin is burned and AC frequency matters as well for AC current. Something as simple as sweaty hands could reduce the numbers drastically as well. OSHA standards for wearing PPE (personal protective equipment) is generally at the Greater Than (>) 40V mark and the types of PPE equipment increases with higher active voltages.
I've seen no literature suggest at any time is the human body <300Ohms total current path short of inserting electrodes directly into the chest near the heart.
That does NOT mean a
circuit powered by say a 9V battery couldn't shock you as there are other electronic devices like capacitors that can build up charges over time (hence how a relatively small battery can power a heart defibrillator (builds charge and then they yell "CLEAR!" in TV shows and movies). I don't imagine any large capacitors being in an iPhone, however.
So
could a 3.7V iPhone (not plugged into anything) stop your heart if you dropped it into the bath tub water with you? I don't believe so. There is no way it could produce 30mA across your heart, let alone 500mA.
The voltage is far too low to produce those current levels. What about a 5V battery cell device that charges an iPhone? The voltage is still too low. But the package says it can produce 1Amp (or iPad even 2Amps)! Yes, but that's not into your body at 500Ohms resistance! It's into the various circuits in the phone that are much lower.
The bottom line is we're not talking about a .22 versus a .45. We're talking about a NERF GUN versus a .45.
How often have you heard of people being
shocked by a car battery (12V) ? I don't mean a circuit hooked up to a 12V battery. If you're sopping wet and some wires were attached and pushed against your skin near your heart, maybe, just MAYBE it could "possibly" cause heart fibrillation (bloody damn unlikely IMO), but generally you don't hear about people dying from handling a car battery unless they ignite acid fumes (explosion not electrocution) or get hit by acid spraying out of the battery (overheat). But a 3.7V iPhone or a 5V battery that charges an iPhone? They're too low a voltage to electrocute a human or stop a heart even soaking wet.
So all I can say again is that Voltage sure as hell
does matter.
What about iPhones catching fire in a pocket? That's not
electrocution. That's the battery overheating and/or exploding (same as a car battery can be dangerous if it explodes).
Now I'm not saying you "should" take a bath with your (not connected to anything) iPhone (it's going to be more dangerous for the phone than you), but this thread is quickly headed into Sci-Fi/Fantasy realms.
The guy in the UK had an extension cord pushing 230V.
I=V/R = 230/500Ohms = 460mA
If his heart didn't stop immediately (percentile chance it did; 500ma is NOT an exact number), it sure as hell went into fibrillation big time within two seconds. Not being able to get out of the tub fast enough while being shocked and with no ground fault interrupter to stop the shock, it's not hard to see why he died. Even if it had been in the US with 120V, he'd still be in fibrillation within two seconds.
But as you drop below 9V (i.e. 30mA), there's virtually no chance of any type of permanent damage (nice chart from a Wikipedia page illustrates below: AC4 is fibrillation/shock with 4.1 being 5% chance, 4.2 5-50% chance, 4.3 being over 50% chance, AC3 is muscle contraction, AC2 is sensation; AC1 is imperceptible.
View attachment 693798
