Why can birds sit on overhead powerlines without getting a shock but humans can't touch them?

Question

This is a question my 9 year old keeps asking me but unfortunately I just can't answer her! Someone help me please!!!

Answer 1

Some of the previous answers are correct. It is about being earthed.

Because power lines carry such a high current they are able to find a path to ground through objects that you would not expect. Things like fiberglass ladders, rubber soled shoes, fishing poles and car tires can form a ground to earth under the right conditions. Moisture in the air and thin layers of dirt on these surfaces doesn't help.

If you dangled from a power line, you would probably be okay too. But if you put your foott on a ladder you would complete the circuit and get a shock.

Your best bet is to avoid contact with the wires just in case your rubber shoes provide insufficient insulation.

Answer 2

Humans could do the same in theory. The electricity passes through the cable the bird is sitting on, not the bird. If the bird had one leg 20' long and it touched it to the ground, it would be electrocuted. Trying to put this so he can understand,.... if you imagine electricity coming from the power station is "+", it travels through appliances to make them work and then back to the power stations "-" side. But at the power station that "-" is earth/ground. So if in the middle of a field a bird sits on the power line, with that long leg touching earth/ground it makes a circuit for electricity to pass and is electrocuted. Because it has legs the same length that does not happen, none of it's body is near "earth" so the circuit isn't made. Hope I haven't confused you even more! :-)

Answer 3

Any creature including human being can get shock only when electric current flows, through the body. To flow the current, the process of circuit has to complete. To explain more correct, there has to be return path, like two wires of which one provides a return path. When a bird is sitting on a single wire, there is no return path for the current, so it does not get a shock. But if it touches two wires of varying voltage, or a wire with part of its body touching the ground, it will get shock because the circuit is complete.Anybody either human or birds gets shock only when the circuit completes.

Answer 4

There is no potential difference when in contact with only one line.

Example 1 - Assume the bird was big enough and light enough to have one leg on each cable then there would be a potential difference between the lines. Due to the way AC electricity is produced and supplied from the generators in the power station. (Sinusoidal wave).

Example 2 - If the bird was in contact with the earth and the power line at the same time, IE part of a conducting ciruit to earth or even just a rail at 0 volt potential then it would also be electricuted.

There must be a potential difference in the voltages for electricity to "flow" as part of a conducting circuit.

Answer 5

The birds aren't touching anything else to complete a circuit.

If we were to touch them we would have to climb something or fly a kite into them and this would complete a circuit into the earth and the electricity would flow through our bodies into the ground.

Don't forget that the metal pylons are not in contact with the cables - they are hung from ceramic insulating discs. If we climbed the pylon and reached out to touch a cable we would link the cable to the metal pylon and the ground and we would get fried.

Answer 6

As long as they have both feet on the wire they aren't earthed. If they had one foot on say a pole and at the same time one on wire, this might go to earth. Perhaps they've got used to doing this the right way through trial and error. Some can mimic telephones, I often wonder whether the throbbing pulse of the calls go through them like a dring dring lol

Answer 7

Because birds are only touching one wire when they sit there, man touches the poles or are standing in those baskets the city provides for them. A PERSON is touching something GROUNDED and the bird is not.

Answer 8

A closed circuit is required for current to flow through it. Power lines have higher potential. When people touch it standing on ground (earth - low potential), current passes through them from high to low potential. If the same individual manages to cling onto the power line without any part of their body touching lower potential, they will also be safe!

Answer 9

if you touch the ground (earth) you will make a complete circuit, when the birds stand on power lines, they are not touching the ground, so they do not get a shock

Answer 10

Well there can be no harm as long as there is no path to ground through their body. Once they are grounded the electrical current can pass through their body. So in essence if you could hang on the wire without touching the ground you would be ok.