Gfyuki

We've all seen this scenario in movies; somebody has to cross a room half filled with water and there is a dangling electric wire that shoots sparks everywhere. The poor person has to cross the room but cannot do so because if the wire hits the water he is obviously electrocuted since water is a conductor.

But is it so simple in real life? If I'm really standing in water in a room, and a high voltage wire hits the water, how does the electricity flow through me to electrocute me? Only my feet are touching the water, no other bodypart of mine is touching anywhere. And realistically there probably would be some piping etc. connected to ground somewhere that would conduct the current to ground. How would I be electrocuted if the current just flows past me?

I suspect this is similar to the well known situation of somebody dropping a hair dryer into a bathtub with a person in it. Why doesn't the current in this situation flow either from the live wire to the neutral wire or through the drain to the ground? Why does simply being in "high voltage water" electrocute me? (And yes, I know the scenario is not so likely with modern appliances but let's consider this in theory).

In something like water electricity does not "flow to ground" in a neat straight line. There is a potential difference between sections of water radiating out from the HV contact point. That might also mean that your feet are at different potentials, and there will be current flow which could be fatal. This is one reason why cows in fields can be electrocuted by a nearby lightning strike. The voltage difference between their feet can be thousands of volts.

Just being in "high voltage water" won't electrocute you, just as birds can happily perch on 10+kV power lines (and linemen can be dropped onto live lines for maintenance work), since there's no path, but as you say, there's always going to be a path to ground somewhere in that water, and so there'll be currents flowing through the water. Since that means that there's potential differences across the water at different points, you'd experience that between your feet, and since the human body is a good conductor, other than the skin, which reduces greatly in resistance when wet, that would allow possibly lethal current to flow through the torso. People can and do get electrocuted standing in salty bilge water on 24V systems on boats, it doesn't take a lot of voltage if the resistance is low enough.

I think that the answer is pretty simple - You are a better conductor than fresh water. i read this somewhere and it made me giggle then: "Humans are just big bags of salt water", which is true. 1mA through heart is enough to cause heart attack, so at 220V 220k resistance is not enough. You are less than 220k, especially when in water. Skin is the only insulator we have.

Just don't try it.

Oh yes. The phenomenon is called "Electrical Drowning".

In this tragic case, a girl decided to dance in a fountain, unawares that the underwater lights had a ground fault. Her muscles contracted and she fell down. 1 friend went in to try to grab her, she too lost control of her leg muscles and fell down. Her 2 other friends tried to rescue the first two.

Firefighters showed up, one tiptoed in, lost it and his friends yanked him out. The firefighters spent 15 minutes trying to find the shutoff switch.

The problem with falling down in water is that you drown. All four girls did.

In fact, multiple victims is often the only clue to an electrical drowning.

This is why any beachside installations now require GFCI and shutoff switches, and why you should not swim near a boat on shore power.

Why electrical drownings happen

You've seen problems involving grids of resistors. That's what water is, a 3-D grid of resistors, and you also are some of the resistors.

Electrical current travels all available paths in proportion to their conductance (1/resistance). 1-10ma is enough to start causing problems for a sensitive person; 100ma is lethal in its own right.

Electricity wants to get back to source (the pole transformer's neutral), and the NEC standard for a grounding rod is 25 ohms. You can do the math here.

Well, I get 120V through a 24 ohm resistor = 5 amps. So only a tiny fraction of that current need go through you to nail you. If we rely on that article's 20ma, then 1/250 of the current is enough to drown you.

Note also: this is not nearly enough to trip a typical 13, 15, 16 or 20A branch circuit breaker.

However, a GFCI breaker will trip at 6-8ma. That greatly improves the prognosis. This narrows it down to a highly improbable combination of events where the current is naturally limited to <6ma, and almost all goes through you, and you're ultra-sensitive.