Why don’t birds die, sitting on power lines?

The high-tension wires of an electricity grid aren’t covered with rubber isolation. They are just fixed on power pylons with the help of isolators and therefore come into contact with only the current source and consumer. 

Nevertheless, it’s not uncommon to see birds sitting on those wires. It turns out, that in this case the birds touch a frayed cord through which much current flows. So why don’t they suffer from this in doing so? 

The fact is that when a bird sits on a wire, the parallel connection of conductors is created. The first conductor is the bird itself, the second conductor is the section of wire under the bird’s feet. The resistance of a bird is many times greater than the resistance of a wire. That’s why very low current flows through the bird and it can’t harm it. (When conductors are parallel-connected, current is shared between the parallel components of a circuit in inverse proportion to resistance). 

However birds can still die because of sitting on power lines. This can happen if a bird touches the metal part of a pylon which hold high-tension wires on which it sits. These pylons are obviously earthed, since they are land-based. Moreover, in this case the resistance of the bird is much less than the resistance of the air with which it creates a parallel connection. That’s why current, flowing thought the bird will be heavy. The current of such power will literally incinerate the bird almost instantly. 

But this is quite rare.

Комментарии

Отправить комментарий

Популярные сообщения из этого блога

Isn't it true that there are blue traffic lights in Japan?

Изображение
If we translate the title of a traffic light go signal from Japanese into English, we’ll get a phrase “blue signal”. But you won’t see blue traffic lights anywhere in the streets of Japanese cities. Their colors are absolutely standard, that is, red, yellow and green.  So what is the cause of this mess?  We should look for it in history. On 8 November 1968 most countries of the world accepted Vienna Convention on Road Signs and Signals which led them to the international standardization of sings and signals.  Nevertheless, Japan decided to take its own path and chose a blue light as a go signal instead of green one. But in five years the authorities of Japan changed its mind and set a green light as a go one. This step was justified by the poor visibility of a blue signal over long distances, because the electromagnetic waves of a blue light dissipate in the atmosphere.  However the Japanese continued to call a green traffic light “ao singu” which means “a blue signa
Далее...

Why do we say "Hello", picking up the phone?

Изображение
Now we perceive a telephone as a perfectly ordinary thing and we can talk on it on any subject, but almost always the first word that we pronounce during a phone conversation is “hello”.  Where did it come from and what does it mean?  Back when telephony started to be introduced into our day-to-day life, everybody who used that novelty had to follow strict procedures. For a long time a phone has remained a working tool for a selected few, as a rule, business and powerful people.  Alexander Bell is considered to be the inventor of a telephone, but the greatest contribution to the improvement of this apparatus and its popularization was made by an American inventor Thomas Edison. It was him who set the word with which a telephone conversation begins in about half of the countries in the world.  In August 2000 Thomas Edison corresponded with the President of one of large telegraphic companies. One of the main themes of their talk was the regulation of negotiation by
Далее...