Probably, each person sometimes wondered why he did not shock birds on wires, seeing a whole flock of birds scattered on a dangerous "perch." Of course, those who remember physics well for the eighth grade can easily explain this phenomenon. But for most people this knowledge turned out to be unclaimed in life, therefore they were safely forgotten. Let's try to restore them.
"Personal protection"
There are several factors that explain why birds on wires are not shocked. First, consider biological, although they are less significant. Firstly, on the legs of flyers there is a layer of keratinized scales. To some extent, they play the role of insulators, although rather weak. Secondly, birds are able to sense the strength of the electromagnetic field. If the power line wire produces a voltage of 500 kV, then the birds simply avoid sitting on it.
It is curious that birds when landing predominantly choose insulated wires. It is difficult to say whether this is another reason why it does not shock birds on wires: perhaps it is simply more pleasant and convenient for them to fix their paws on insulation. Although some scientists have the opinion that this also works protective sensitivity of flyers.
Why birds are not electrocuted when they sit on wires: a physical justification
The physical explanation of the phenomenon is much more significant. To begin with, in order for the feathered to be “jerked” by the current, it must go through the bird’s body. And this requires the presence of a significant potential difference between any two points. In this case, between the legs of the flyer. However, it sits on one wire, the voltage in which does not change throughout. Accordingly, no differences are observed. Moreover, if we consider the bird as a branch of an electric circuit, then its resistance is much greater than the resistance of the wire itself. So the current goes through the area where its "path" is facilitated.
It is explained somewhat differently why it does not shock birds on wires with very high voltage. Through them is not direct current, but alternating current. In this case, the feathered body becomes, one might say, a capacitor: charge first accumulates in it, and then discharge occurs. Since the body of the bird is small, its capacity is also scanty, and the current passing through the flyer is not dangerous. The larger the linear dimensions of the object and its volume, the greater its capacity. So, for example, if a stork sits on a high-voltage wire, then such a landing will not end in good for him.
When nevertheless "pulls" the current
Note that the birds still sometimes die when using wires as a perch. This happens when some third point (most often the wing) comes in contact with another wire or pole supporting the line. In both cases, a potential difference occurs, and a current begins to flow through the bird's body. Most often this happens with relatively large birds like crows, whose wingspan may be greater than the distance between the wires.
