[ELI5] Why is the difference in potential of electricity the one that kills you?


I found something on reddit about this. Basically it goes like this:

If there is a broken live electrical post falling down on your vicinity, you need to hop up and keep your feet close together instead of walking.

The explanation for this is that if your feet are far apart, there’s a difference in potential between your feet. How does this work?

I really don’t understand what the internet says and maybe someone could get me the answer if it’s eli5’ed to me. Thanks reddit!

In: Physics

Well, that’s an awkward way of saying it… I THINK

What I guess they are saying that if your feet are separated, one foot thats in the air could get shocked and there is less resistance for the electricity to go through your body than the air gap. And if your feet are together, you wont get shocked through your body???

That seems like an unreasonable distinction. The difference in potential within the body is barely anything. Pointed objects tend to attract arcing electricity because the concentration is of charge is greater, but I don’t think that is relevant either.

edit: Moral of the story is don’t walk around live wires.


If I place a ball on a tabletop and give it a shove, it’ll roll off the edge and fall to the floor. If I do the same thing but put another table of the same height right next to the original, the ball rolls onto the next table and doesn’t change height (it doesn’t fall anywhere).

Electricity does the same thing: it wants to move from high potential (on top of the table) to low potential (the floor). It doesn’t matter how high the table top is or how low the floor is as one as one is higher than the other. The bigger the difference (really tall table) the more energy/speed the ball gets as it falls. Similarly, the higher the potential difference you see, the bigger shock it can give. A 9 volt battery can tingle your tongue because the potential difference between the terminals is only 9 volt. A wall socket has a potential difference of 120 volts, which’ll turn your tongue into a well-done steak, because it’s metaphorical table is now as high as the Space Needle.

You’re probably thinking of something like this video where it recommends shuffling https://youtube.com/watch?v=fLVzvMTgGDY (I included a video from a reputable source because I don’t want to risk giving bad information on something life or death)

What happens is that electricity wants to find the easiest way to go from one location to another. if you spread your legs then you might conduct better than the ground that you are crossing. Because it’s easier to go through you, a flexible bag of mostly water , than it is to go through that dry ground. if you have very short steps then it is easier for the electricity to flow across the ground than it is to go through you

In a lot of ways, electricity is like water flowing. Both electricity and water go down the path of least resistance. Both try to spread out to equalize pressure.

Lets say you have one foot on the ground and it is very electrically charged due to a power line. A portion would go into your foot just because your body has less charge than the ground, and like water it’ll try to release pressure where there is less pressure. Think of that like water bottle full of air connected to a water valve. a bit of water would flow into it, but not much before the water/air pressure pushes back to stop any more getting in. That’s not great, yet not as bad as it could be. Place two feet together, and it’s mostly the same thing. Electricity flows in both legs equally since the charge or ‘pressure’ is more or less the same where both touch the ground. Once you have as much charge as the ground the current stops. You are no longer the path of least resistance since that extra charge given to you equalizes the ‘water pressure’.

Place your feet apart, and it’s less like a bottle and more like a tube. If one end of the tube there is more pressure than the other, the water will flow from the high pressure portion to the low. If for instance the electrical charge on one foot is higher because it is closer to the downed power-line than the other foot, that charge may choose to flow through you rather than the ground if you offer it less resistance than the ground. This flow or current is what’s damaging to your body as it causes intense heat. It is particularly damaging if it flows through your heart on the way from one foot to the other since the electricity will paralyze your muscles.

That’s why many electricians work with one hand at a time when they can rather than both. A charge may move from one hand to the other, and cause their heart to seize up along the way.