Obviously if we put live electricity in the sea, the whole ocean wouldn’t then become dangerous with it. At what point does the electricity stop? What stops it?
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Every time electricity moves, it uses a tiny amount of power to do so and will always move if there is room to do it. In water, it can move freely in any direction, so in other words, it can move A LOT.
With that in mind, the more power electricity has at its source, the further it will go, BUT, the further it goes from the source, the less power it has at its end.
So that means a big amount of power, will move further away then a small amount of power.
This concept is actually what grounding is, we use the earth (the wire connected to ground) to release unwanted power safely, so that components and people can continue to use their electronics if there is ever unwanted power that needs to be released.
In seawater the voltage gradient around electrodes displayed within a short distance, so the dangerous area is very close to the energized electrode or the spot the lightening strike the water.
In freshwater, the voltage gradient extends further and a human body in the gradient becomes a lower resistant path for electricity, so
Electricity in fresh water is more dangerous to people in the fresh water with the electricity.
Okay, so if I was in the ocean though…and lightning struck 2 feet away from me to the water, would I get shocked?
There are a lot of variables.
For starters, pure water almost isn’t conductive. The more minerals/salt dissolved, the more conductive.
Secondly, the voltage would heavily impact the distance too.
This is one of those questions you would put in a physics class after like 2-4 days of studying the relevant math.
Answer: Inverse Square Law
The distribution of the charge increases by the square of the distance – think of the surface of a balloon as it get bigger if it double in width, the area of the surface of the ballon increases by width to the power of 2 (the square).
So as potential charge is then distributed on a bigger and bigger area the further you get and pretty soon it is almost not there
At the edge of the universe there is a planet, let’s call it planet mouse, that planet feels the gravity of earth, even though its billions of light years away… It is completely inconsequential to it because the effect is so small as to be functionally non existent. If you make part of the sea live with electricity, all of it is… Just at some distance it’s so small that it’s functionally nothing.
Drop something into a puddle. See how the water waves are big next to the thing, but slowly get smaller? When lightning (or any electrical current) strikes the water, the electricity slowly goes away the farther away you are from it.
Roughly the same way that a sound you put in the atmosphere gets less loud with distance. It spreads out, which delutes the energy. Technically it never realy stops anywhere, but it gets so feeble that you can’t practically detect it anymore against the background noise.
Not an answer but an anecdote…
When I was young, I had a fish tank heater, basically a heating element inside a glass tube, but the glass tube had broken. I plugged it into the house with a long extension cord and would go to the canal abutting my house and submerge the heating element, then turn it on. (It was an easy way to catch fish.)
One day a friend was with me and he wondered how far the electricity went. So he got in the water about 10 feet away and started walking toward me. He started feeling it as he got closer.
Another anecdote…
I was sailing a dinghy and a storm came through. I was knee deep in the water trying to get the boat ready to be put back on the trailer when I saw lightning strike the water, maybe half-mile away. I felt the electricity up my thighs. After the third strike, I decided the boat wasn’t worth it and got out of the water. (I came back after the storm and finished it then.)
I just watched the Slow Mo Guys video with Electroboom where they show electrical arcs at 1.75 million fps. I would really love to see them tackle this one.
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