I understand why you get harmed if you’re grounded, you’re becoming part of the wire and the electricity is going from you to the earth. what I dont understand is, why the electricity doesnt harm you when youre not touching the ground, isnt it going through you either way? how does it not affect your body?
In: Physics
Electric potential is relative. Voltage ratings are given as their potential from ground. If you are not grounded, electricity cannot return to source. Therefore, no current can pass through you. At the same time, you nearly instantly become the same potential as the wire.
Well where would it go? Through your body and back into the wire? Electricity takes the path of least resistance and the wire is much less resistant than your body. So almost all the electricity will stay in the wire and extremely little goes through your body if there is no path to ground or back to the power source through the body that shortcuts large parts of the circuit.
No, it won’t go through you if you’re not grounded.
Let’s think about what it means for electricity to go “through” you. Electrons jump off the live wire into your hand; this pushes electrons from your hand up into your arm; and so on, until electrons in your feet are pushed into the ground.
But if you’re not touching the ground, that can’t happen. At best electricity could go *into* you, static-electricity style, not *through* you. And since your body is already basically full, in terms of how many electrons it can hold, there won’t be very many going in.
Electricity has two key parts: voltage and current. Voltage is the potential for electricity to flow, like a pressure that wants to push electricity through things. Current is how much electricity is flowing through a thing. Generators and batteries can make voltage, but it is always between two things, like two wires. If you just touch one wire the electricity cannot flow. In order to make things safe one of the two wires is often connected to “ground”, which is done partly to make sure that if a stray wire touches a metal enclosure a lot of current will flow and the breaker will trip, instead of electrifying the enclosure and zapping you when you touch it. Because a lot of circuits are grounded, it means that if you do touch a live wire, you may be also touching the second wire, if you are touching “ground”.
Yes.. but don’t.
Birds can land on a live wire because, though they are touching the wire they aren’t touching anything else and the there is no path for the electricity. High voltage isn’t harmful if there’s no current flow, but they can get a bit of a zap when doing this as they go from zero volts to, say, 350 kV.
To do the same a transmission line worker can wear a metal suit that guides the voltage around their body and first contact the line with a ‘hot stick’ that allows them to be charged to the same potential as the line.
Or a high school teacher can touch a Tesla coil while standing on a stool. Same principle, just a lot less energy and risk.
In order for current to flow, there needs to be a circuit, i.e. a loop. If you were to hang from a live transmission wire, and be far enough away from other stuff to avoid arcing, then you’re not closing any sort of loop, you’re just there. You’ll be charged to same potential (voltage) as the wire, and for AC there will be small currents flowing in and out of you as the line charges and discharges you, but since you’re not actually making a path to anywhere there’s no *net* current flow through your body. Basically, it doesn’t have anywhere to go through you, so the current continues along the line. Still wouldn’t recommend, but technically you’d be safe.
Whereas, if you were standing on the ground, the Earth becomes the return side of that loop, and now you’ve made a nice path for a *lot* of current to flow through you. Now, it’s much easier for the current to flow through you than through the rest of the line, and since it’s way easier most of it’s going to flow through you.
“If you jump into the air and grab a live wire, you won’t get electrocuted. But then if you land on the ground and you’re still holding that wire, you’ll be blown to bits. I saw it in Tango and Cash. “
If there’s no current then the electricity isn’t going through you. You would still charge up to that potential and your hair would stand on end etc but there’d be no resistive heating (current squared times resistance) therefore no burns.
Like water, electricity flows from “high” to “low”. Imagine two bodies of water, where water from the higher one flows down a waterfall to the lower one. If you were sitting at the top of the waterfall, nothing really happens to you (unless you’re trying to block the water from flowing). If you were at the bottom of the waterfall, the water slams through you.
Everyone else has already covered the flow aspect of electricity, but it’s worth noting that ground isn’t the only thing that could endanger you. If there was an open circuit (e.g., if you cut a power line) and you grabbed both ends of the break then you could also be electrocuted.
For a practical example, when you lick a 9V battery (obligatory disclaimer, every kid does this but be careful) you are creating a circuit across the two terminals, and ground has nothing to do with the current you feel.
Ground is by far the most common source/sink of electrical energy we encounter, but any flow could harm you.
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