Subject: 站在電線上的鳥類會否觸電死亡? Birds on overhead lines [Print This Page] Author: HKBWS Chuan Time: 4/11/2011 14:46 Subject: 站在電線上的鳥類會否觸電死亡? Birds on overhead lines
有位中學生詢問為何站在電線上的鳥類不會因觸電因而死亡, 請問有沒有熟悉物理的朋友能解答呢?
A secondary School student asked why birds on overhead lines would not die of electric shock. Any friends who know physics well could answer? Author: cyanophile Time: 4/11/2011 15:00
Birds won't be killed by the overhead lines.
Although the overhead lines are of high voltage, the overhead lines are very very long (several kilometres or more) . Therefore, the voltage difference between the head and the end of each small segment of the overhead line is very small, while the electric shock actually depends on the voltage difference. Imagine, a bird only stand on a very very small segment of the overhead line (a few centimetres) , so the voltage difference is way too weak to kill the bird.
This question is usually discussed in form 4 form 5 physics XD
Please correct me if I am wrong (time to revise some physics ^^ )
[ Last edited by cyanophile at 4/11/2011 15:07 ] Author: ajohn Time: 4/11/2011 16:31
My understanding was that birds did not get a shock because they do not complete a circuit. The birds are in contact only with the wire, so the electricity cannot flow through them. If they were touching the ground (or another object - tree, pylon, etc.) the wire would be earthed and electricity would flow through and kill the bird.
Apparently there are many cases when larger birds (vultures, storks, swans) have flown into wires and made contact with two separate wires - this creates a circuit and the bird receives a shock.
(I think this explanation is not actually different from cyanophile's response. The bird perched on a wire actually can create a circuit between the two feet but the voltage difference is very small and won't cause a shock, it is only when the bird is in contact with another object that it creates a voltage difference large enough to be felt.)
Are there any physicists who can comment? Author: 9Wi Time: 4/11/2011 16:40
Before you touch a high tension electricity power line, there is a huge potential difference between you and the wire. When you touch the wire, a burse of electric charge would flow for a very short moment only (assume there is no closed circuit). During that short moment, the charge involved is very low (although the electric potential difference is very high). Overall the energy involved is small, may be enough to create a tiny spark of electricity to your hand. Still, nothing serious.
In summary, if there is no closed circuit, static electric charge cannot kill you.
Another example on the same topic: How does the electric mosquito racquet work? Can you identify the closed circuit when there is a mosquito?
HF Cheung
[ Last edited by HFCheung at 4/11/2011 17:51 ]
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