So as we know for a person to get electrocuted a circuit needs to be completed. You cannot stand on a wooden chair and get electrocuted. So when you stand on a wooden chair and touch a live wire, how does the electricity figure out that you’re standing on an insulator? Does the electricity pass through you first before failing to complete the circuit because of the wood?
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The electric/magnetic field that is essentially the wrangler of electrons sets forth a path of least resistance and the electrons follow that. The electrons do not know anything. They just follow the complex fields all around the system and all around us.
Think of electricity as traffic on a road and that electrons are safe and considerate drivers.
An insulator is a like a red light. Traffic stops because everyone has a car in front of them all the way up to the one car stopped at the traffic light.
Once the light turns green, the first car can move, which means the next car can move, etc. etc. etc.
A live wire just sitting there is like cars at an intersection with a red light *and* the road in front of them is full of traffic, they can’t move (despite the light color) because there is *no where for them to go*.
Once I touch a live wire, that’s like the light at the intersection turning green. The cars *can move* but only if there is somewhere to go. If I’m fully insulated that’s like my road being full of cars. Even though the light is green, the cars can’t merge onto my road because it’s already full of backed up cars.
But if I become uninsulated that’s like my road clearing. If both my road is clear and the traffic light is green (I’m uninsulated and I touch a live wire) then suddenly the cars will rush onto my road. That’s electrocution.
This is kind of like asking “how does your car know to stop when there’s an accident miles ahead of you”.
In a circuit, electrons are flowing in a particular direction. If the circuit isn’t complete (or, if you prefer, if the resistance in the circuit is extremely high, which is the same thing), those electrons begin to pile up and the flow stops, in much the same way that an accident stops traffic. Since ~~electrons flow~~ electricity flows at extremely high speeds (a meaningful fraction of the speed of light), the “traffic stops” more-or-less instantaneously from a human point of view, and the current instantly drops to near-zero.
Think about it like opening a door. It doesn’t flow through you because you haven’t opened the door for it to go anywhere. It’s already grooving in its current circuit. When you open the door by completing the circuit it has somewhere to go.
How does the water at the surface of the bathtub know that the drain at the bottom has been opened? It doesn’t, directly, but the water at the bottom of the tub is flowing through the drain and no longer resisting the weight of the water at the top. The water level starts going down because of that lack of resistance at the bottom.
It’s the same with possible electrocution: a lot of electric charge is suddenly pushing at one end of your body, but if there’s an insulator at the other end, all the other charges in your body pushing against the insulator and against each other will cause them to brace against and resist the incoming charge.
Electricity doesn’t “know” or “think” about anything. It behaves according to Physics.
Think about water in a glass. How does it “know” to take the shape of the glass? It doesn’t. It’s just this pile of water atoms that’s being pulled towards Earth by gravity, but the glass is in its way, so the atoms arrange themselves in a pile such that every atom has moved as much as it can and that happens to make the water fill the glass’s shape. It’s not that much different from if you put a lot of sand in the glass.
Electricity flowing down a wire is like water flowing through a pipe. Think of an insulator as a really skinny pipe, like a drinking straw skinny. Think of a conductor as a really big pipe, like a sewer big. If a lot of water is flowing down the sewer and there’s a tiny, straw-sized pipe off to the side, *some* water is going to go down that tiny pipe but not an awful lot because you just can’t fit “big pipe” water into “small pipe” space.
Or, put another way. Suppose I have a big water tank and water’s coming through a fire hose. At the end of the hose, I put a T joint, with one direction funneling into a tiny pipe and another direction funneling into a big pipe. If we measure what’s coming out of both pipes, it’ll be the same amount of water that is in the hose, but far less water will come from the small pipe than the big pipe because less water “fits”.
That’s how electricity moves. Instead of gravity, electricity moves in the direction of “potential difference” which means it tries to get from a place where there’s a high voltage to a place where there’s a low voltage. Think of voltage differences as sort of like a magnet: they suck electricity from where it is to where it isn’t. But also think of it like gravity affects water: if the “pipe” the electricity is flowing through is small (a conductor) it’ll flow VERY slowly.
So let’s say somehow we’ve charged an orb with 10,000 volts. The electricity just sits there, because air is a pretty decent insulator and there just isn’t enough energy in that electricity to push through the teeny tiny pipe that air represents. This is like a bunch of water sitting in a glass. It feels gravity and wants to go to the ground, but there’s just no good path.
Your body is a half-decent conductor. But if you’re floating in zero gravity and you poke the orb, since your body isn’t touching anything at a different voltage not much happens. You might absorb some of the charge, but since the electricity isn’t flowing *through* you we can sort of see it as like you’re “wet” with electricity. It STILL wants to get to the ground but there’s just no path, and it’s the movement of electricity that can cause damage to your tissue.
Now let’s say you barefoot touch the ground. The Earth doesn’t really have a significant charge compared to that 10,000 volts, so it’s going to push itself through your body into the Earth and you’re likely to get hurt from all that energy flowing through you.
But what if instead you barefoot stand on a thick rubber mat? That’s a strong insulator, so there’s still no easy path to the ground. If we do some serious math we’ll notice some tiny amount of electricity will trickle through, but it’s so negligible you won’t feel it and it’ll take ages to see a measurable difference.
So it’s not about electricity “knowing”. It’s about whether the path to the ground it has is a thicc pipe or a smol pipe. Also notable: if the voltage gets high enough, it CAN arc through air and could even push its way through a rubber mat. Imagine trying to funnel all of the water behind the Hoover Dam through a drinking straw. It’d destroy the straw because there’s just so much pressure.
(This is all a little hand-wavy to keep it simple, there’s also the concept of “current” I could’ve discussed. But in general, if voltage is really big current is going to be bigger, and if the “pipe” is “bigger” then current can be bigger, so adding it in makes things more complex for no good reason.)
Electricity is the flow from an area of many electrons to an area of few electrons.
Earth, compared to most anything on it, always has few electrons.
An “insulator” is a substance with either enough electrons, a slight abundance itself, or is merely non-interactive with electrons.
Electrons always follow the path of least resistance.
So it isn’t that the electrons “know” but more that an insulator is not a path electrons can follow. It is a cap versus being a hose.
Say you’re standing barefoot. The live wire is a high-potential or high-voltage or high-electron thing insulated by the air.
You are mostly water and water with electrolytes – your skin and salts in your body – is a very good conductor.
To electricity, you are another peice of hose running into the ground where the electrons can go and spread out and bot be so tightly packed together.
Put on rubber shoes and these cap you off from the earth.
Similar to how others have mentioned another way to look at it is like water (funny enough a lot of equations for fluids and electricity are similar and they actually behave very similar).
In your own example of standing on a chair and touching a live wire, the electricity is already completing a circuit through the wire and back to “ground”. You can think of the same example as a pipe with water coming to a T- junction. One of the 2 paths is closed off, which is the same as what the electricity encounters with you versus continuing down the wire. High resistance in a circuit is like hitting a brick wall.
That said, just like in a pipe with water, if you increase and increase and increase the flow rate (gallons/minute for example), the pressure will increase because the resistance (size of the pipe) remains the same. Eventually it will break through that wall of the blocked path at the T- junction and flow down the other path as well.
The flow rate, or current (amperes) in the case of electricity, works the same way. Increasing the current or potential difference (voltage e.g. pressure) high enough, itll flow through you and the chair.
I want to point out another relevant fact that address your fundamental misunderstanding. Other people had given you various analogy like “stuck in a traffic jam”, but you don’t even need that to explain the phenomenon. Electron is capable of detecting things far away from the path that it moves. Even when you have a single lone electron, it is capable of detecting multiple future paths and know which one is hard to move through and avoid moving there in the first place. So you don’t even need a “stuck in the traffic jam” analogy to explain this phenomenon.
A different analogy is like this. Imagine there is a car come across a fork on a lone road, one path has a collapsed bridge miles ahead. How do the car avoid the road with collapsed bridge? It splits into 2 copies of itself, and move on both path. The copy that the reach the bridge stops, but the other one arrive. At the end, when asked about what happened, the car only know that it go through the unobstructed road because the copy that see the collapsed bridge never arrived, so from the outsider’s perspective, the car avoid the road with collapsed bridge as if it knows.
Yes. The electrons basically push into your body in a tiny fraction of a second, then once your body has a few too many electrons, they repel the other ones trying to come in. If there was a complete circuit, they would keep going in one part of your body and out through another part.
That’s for DC of course. AC is just DC that changes, so the same thing applies, but it reverses 100/120 times a second. It’s still pretty tiny even when it’s happening 120 times per second.
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