Fatal Shock

  1. A bird perches on a bare high power line and nothing happens to it. A man standing on the ground touches the same line and gets a fatal shock. This is supposed to be because there is potential difference between the ground and the line which the man touches but similarly, isn't there also a potential difference between the line and the air to which the bird is exposed and thus a potential difference and so shouldn't the bird also get a shock? I know that air is an insulator but since the high transmission lines have large electric fields around them so this should cause breakdown of air?
  2. jcsd
  3. SteamKing

    SteamKing 11,033
    Staff Emeritus
    Science Advisor
    Homework Helper

    The breakdown voltage for air is much larger than the line voltage. The field strength for the breakdown of air is greater than 3 MV/m. If electric transmission lines grounded with the air, it would be impossible to transmit electricity in this fashion without zapping everything near the lines.
  4. UltrafastPED

    UltrafastPED 1,912
    Science Advisor
    Gold Member

    Also note that you, as a person, are not a great insulator ... and being the path of least resistance is from the line voltage thru you to the ground.

    If a bird is big enough to touch two wires simultaneously you will get roast buzzard!
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