Why do humans get electrocuted when touching a live wire without even touching the ground?

Question

refer to the case of the bird sitting on the live wire if you wish

Answer 1

They are electrocuted (I mean die from that) only if they close the circuit through their trunk in some way, and if the voltage *difference* at the ends is enough. You can still have an "electric shock" but not die if the circuit did not close through the heart or if it did not last for too long.

People usually die because the electricity prevents muscles to get any command. In this case the electricity going through the trunk may stop the heart or stop breathing. It's because the control signals (though nerves) are electrical signals and they are blocked by the current.

You can get a high potential and not be electrocuted at all IF everything you touch is at the same potential. For example, I have been in a special machine where I was completely isolated from ground and where any part that I could touch was at the same potential. Then they charged th machine, I did not feel nothing excepted that my hair were straight up on my head... while outside they made big sparks from the machine to the ground. But no electricity was going THROUGH my body because there was no potential difference between any part of it.

Is it possible to have a shock touching only one cable ? When someone touches a power cable with 2 hands, there is a potential difference between the hands because of the cable resistance and the current in the cable. This voltage is the product of cable resistance by current. And the resistance is proportional to the distance between hands. The current in high voltage cables can be big, the maximum being around 2500 A. The resistance of the cable (for such high voltage cable) can be 0,1 Ω/km. Thus for a 2m distance between hands, the resistance will be 0,0002 ohms. The voltage is thus V = R x I = 0,5V. Not at all enough to kill anyone.

Answer 2

If the 220v of batteries were connected to your house in the same manner as the transformer out on the power pole you would be killed by that too. There are three wires coming from the power co. transformer into your home between the "neutral" and either of the other two (live) wires there is 120 volts and you will measure 240 volts across those 2 live wires. In the box that has the electric meter in it you should find a small (1/2") conduit coming out of the box going down to the ground which has a ground wire in it that is attached to an 8 or 10 foot long rod that is driven into the ground. This ground wire is connected to the neutral wire inside the meter box, so if you were to put one probe from a volt meter into the ground and touch the other to one of the live wires you will read a voltage close to 120 volts. Now with your batteries this connection to the ground does not exist so you would measure nothing from the battery terminal to ground. The circuit that would be created if you were to stand on the ground and then touch one of the live wires would carry enough current to kill you (I think you only need .007 amps to do that) but not enough to run an appliance. I AM NOT recommending you do this but if you were in a house with a good dry wood floor (good insulator) and touched the hot wire in the outlet WITHOUT touching anything else but the floor you will not even have enough current flow to even feel anything or be injured. This is the theroy that the GFCI is based on, as long as current takes the path through the load as it is intended it stays on, if you become part of the circuit (a current leak to ground) then the current thru the live and neutral wires is no longer equal and the breaker trips. I think this should help you understand why the power in the house would kill you and the batteries would too if they were grounded like your house is. Email me if you have more questions.

Answer 3

we're the same with the bird. the only thing is, the bird is totally insulated from any other object with a voltage different from the cable.
the thing is, if you touch the live wire whilst on the ground, wearing shoes or something, depending on the type of shoe, you could get electrocuted. the same applies because if you consider how arch welding is done, you do not need contact with another object at zero or negative voltage for the path to be made. if the voltage is large enough, there will be an arching effect (movement of power in air, similar to how lightning works) and thats how you would be electrocuted.
if you were to hang down from a poer line, if the voltage on the power line is less than a certain creitical value (calculated using electric field strength formulae), you wouldnt get electrocuted. but if it is higher than that, you'd be fried coz of the high electric field coz you'd provide a shorter distance between the two potential differences, enabling an arching path.

Answer 4

If you touch a live wire, and are in no way connected to the ground, then in principle you shouldn't get electrocuted.

However, if the voltage supply is big enough, then a gap between your feet and the ground (air) could be overcome by the voltage potential between your feet and the floor. Just as in the case where thunder storms create an electrical link between the charged clouds and the ground. Air is not a fantastic conductor, but if the voltage is enough, then the electricity will find ground through it.

Answer 5

No. You can touch a live wire on your mains supply and not get a shock. It is when you complete the circuit via another wire or earth that you get the shock. You could walk along the live rail on an underground train system without a shock but put one leg on the other rail and puff.
The only time that you might get a shock when hanging from an overhead cable is if the air is damp and the electricity tracks through it to a suitable point. Best thing is to stay away.

Answer 6

Electricity will flow towards the path of least resistance. Birds on the wire dont get electrocuted because the electricity would rather flow through the wires than to the birds.

Answer 7

If you touch a live wire, and there is a path to ground you will get a nice shock. Many floors conduct electricity very well and are only a few ohms to ground. My new work safety shoes say protection to 600 volts, so I am going to touch a small live wire soon and give them a test. Only 120 volts and see it I get a charge. Well maybe I will maybe I wont.

Answer 8

I don't actually know many people capable of levitation.

Everyone I do know would be electrocuted when touching a live wire unless they were insulated from the ground.

Answer 9

The same applies to humans as well as birds, But electricity can jump through the air, eg electric ignitions, Lightening. It is reckoned 1000v can jump 1 cm given the right conditions. So if you are too close to an earth, you can still get fryed.

Answer 10

The size of the body matters. The larger body has large electrical capacitance, which means more current can flow into it to build up a charge. That current must flow through the body. For an AC wire, the current flows in on one cycle, and out the other, so the body is continuously carrying current.