The body is roughly a "bag" of moderately-conductive (10 to 100 ohms point to point) liquid with a decently insulating outer coating (stratum corneum of the skin) which has tiny holes in it. Sweat can provide a conductive path through these holes (sweat ducts), although the resistance is fairly high because the hole diameter is small and the density of holes isn't very high. There is also capacitance across the skin and within the moderately-conductive fluid inside. This does allow AC to cause more current flow than DC. The water in the tub is also only moderately conductive. When the contacts from the cord get immersed, there is a distributed current flow through the water and (if you are in the water) through you. The large contact area of the water (with dissolved ions) and your skin means that many of the sweat ducts are in contact with the water and the overall resistance offered by the skin is reduced. At this point, you essentially look like an equal volume of impure water and become part of the current path. Likewise, it is MUCH easier to be killed or injured by low voltages if you break the skin and allow direct contact with the fluid inside. 9V could definitely kill you given the proper attachment points to direct the current flow through vital organs. Higher voltages quickly cause breakdown of the skin due to heating and electrochemical effects from the high current density in the tiny sweat ducts. After the breakdown the current grows to a value only limited by the internal 10 to 100 ohm resistance and often causes burns. The nerves are the most sensitive to electrical disruption since they rely on electrochemistry to send signals and they normally work with only 10s of millivolts of signal. Current flow through nerves causes pain and also muscle contraction. Higher current levels can also directly stimulate muscle contraction. DC tends to cause continuous contraction. AC tends to cause vibration and loss of voluntary control. A current path through only a limb is likely to be painful but not permanently damaging unless it causes thermal damage or nerve damage. Very violent muscle contraction can also tear muscles or tendons/ligaments. Thermal damage can rupture blood vessels if the current is very high. A current path through the brain will often cause an immediate seizure and can lead to nerve damage in the brain. Death can result - especially if the brain stem is affected. A current path through the heart will often cause a disruption in the rhythm which can degenerate into ventricular fibrillation. A current path through the abdomen can paralyze the diaphragm muscles and prevent breathing. Generally, due to the increased impedance (no capacitive effects) and the slightly reduced disruption of nerves due to continuous rather than pulsed stimulation and also the greater chance of a muscle contraction throwing you away from the source of the current, DC is somewhat safer. For DC current, about 1mA is the threshold of perception and also generally considered a maximum acceptable safe level. 10mA is quite painful. 20mA can cause some muscle paralysis which may make breathing difficult and may make it impossible to let go. Around 50mA is where death is possible, but 100mA is considered the point where ventricular fibrillation is likely if the current path is right for it. For AC, I've seen various figures but it seems like AC is about 3x worse than DC when you consider the RMS current value of the AC (peak value is about 40% higher). So, 300uA can be felt, 3mA hurts but is unlikely to kill you. 6mA can cause inability to let-go. 20 to 30mA is where things get really dangerous and 50mA is likely to kill you if untreated. As you can see, if the skin is broken, only 5V is needed, under optimal conditions, to produce 50mA with a point-to-point body resistance of about 100 ohms. With the skin intact, it depends greatly on the contact area, contact pressure, how much sweat is present. The effect is also very non-linear because there is a positive feedback effect that more current causes more heating which causes lower resistance due to skin beginning to break down. On Tue, Jun 6, 2017 at 11:18 PM, Neil Benson wrote: > My question is the HOW of electrocution: my understanding is that while > standing in a grounded tub of water, if a live extension cord is dropped > into the tub--I die. > > What is the physiology? (I can understand sterilization), why death. In > fact, why anything? Is the body CAPACITANCE so large that significant > current flows? In this case I would not expect that the tub needs to be > grounded. > > Is DC safer? > > I've read the story of a guy killed when he attached a 9 volt battery > between his hands--INTERNALLY, not just surface. But is DC safer in the > 'standing in water' case? > > I'm aware that most forums prohibit health advise (other than: See a > doctor), so this is a science question. > > > > On Tue, Jun 6, 2017 at 9:28 PM, John Gardner wrote: > > > ...will his genes be passed on to another generation? > > > > They got this far - Probably more involved than one idiot... > > > > On 6/6/17, Sean Breheny wrote: > > > The worst electrical shock I've gotten was from plugging in an 120VAC > > cord > > > which had a single strand of the stranded line cord sticking out wher= e > > the > > > plug met the cord. This was outdoors and I was standing barefoot on > > > concrete. > > > > > > A close second was the time I was doing ESD testing at 15kV, was > > > accidentally touching the unit under test AND was holding the ground > clip > > > against a bolt in the floor to ground it (and happened at that instan= t > to > > > have unknowingly lost contact with the bolt). So, it was a direct > > > across-the-chest hand to hand 15kV shock, thank God it was from just = a > > 1nF > > > capacitance or I'd be dead. Definitely woke me up! > > > > > > I also once had a funny experience where two of us were debugging a > motor > > > drive which used 20kHz, 50V PWM. We were feeling around the PCBA on t= he > > > tops of components to feel how warm things were getting. My coworker > > asked > > > why a particular IC was getting so very hot when it wasn't supposed t= o > be > > > a major heat dissipating component. I also went to feel that part and > > > initially it didn't feel warm but I moved my finger a bit and it > suddenly > > > felt very hot. After more investigating I discovered that it wasn't h= ot > > but > > > it was right next to an exposed terminal which was connected to the > PWM. > > If > > > your finger happened to touch that adjacent terminal, it produced a > > > sensation unlike any other AC or DC electric shock I've ever felt. It > > felt > > > just like touching a hot object. I guess the high frequency caused a > > > different kind of nerve stimulation. > > > > > > > > > > > > On Tue, Jun 6, 2017 at 6:18 PM, James Cameron > wrote: > > > > > >> Either way, he was electrocuted by his choice to use his phone, and > > >> that matches an anticipated narrative, feeds the fear, and is > > >> therefore good click bait. We should expect no less from story > > >> writers and editors because that's how they are funded. > > >> > > >> I'm reminded from my own experiments that submerging is not required= ; > > >> condensation is enough to make a path. > > >> > > >> -- > > >> James Cameron > > >> http://quozl.netrek.org/ > > >> -- > > >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > >> View/change your membership options at > > >> http://mailman.mit.edu/mailman/listinfo/piclist > > >> > > > -- > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > View/change your membership options at > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .