Here’s an easy one but nevertheless, I am completely ignorant on this subject. How come if I touch a power line I’ll be killed instantly, but a bird can land on it without being fricasseed? How about squirrels? My boyfriend said it had something to do with grounding but that didn’t make much sense to me.
short answer:
Electricity (as commonly understood) only exists in a circuit, a path from higher voltage to lower (aka ground). If you were to touch wire (and nothing else, not even the ground) nothing would happen. No path to lower voltage. Birds or squirrels survive this way, usually. Occasionally one will touch another wire, tree, or pole and get fried.
longer answer:
Actually, some current does flow through the small animals if they touch the wire in two or more places. But, because their bodies have a much greater resistance than the wire itself, it is a very small (very likely un-noticed) current.
Other regs can probably answer this better, but, for once, I get to be first. 
I remember when I was in Great Lakes, IL, occasionally seeing dead birds under a power pole. A local told me that sometimes the birds would huddle on the crossarms in cold weather till they bridged the two conductors. Made sense to me at the time, but is this true? I know how Chicagoans love to bullshit. I have seen birds do this (huddle) but never saw them actually get zapped.
Peace,
mangeorge
Work like you don’t need the money…
Love like you’ve never been hurt…
Dance like nobody’s watching! …(Paraphrased)
Electricty, to put it simply, always seeks the shortest route. If a bird is sitting the current doesn’ go through the bird as it isn’t a shorter route… If the bird touched the ground and the wire it would create a “short circut.” And that is how the Colonel invented fried chicken.
A bit oversimplified but…
Mangeorge,
Yes, it could happen that way.
Ranger Jeff
*The Idol of American Youth *
Umm, not to shoot all or your ideas down, but aren’t the wires, um, INSULATED? I suspect that that has more to do with the happy little wire-bounding squirrels survival than it’s electrical resistance.
The wires are insulated… by those funny-shaped glass/ceramic/whatever things holding them… and by the air.
Power lines on towers don’t have continuous insulation on the wires, partly because the extra weight of the insulation would require stronger and more expensive towers. They rely on sufficient thicknesses of air to insulate between wire and wire, and between wire and ground. Air is much cheaper, doesn’t load the towers with additional wight, and already surrounds the wires.
The greater the voltage, or electrical pressure, between two points (such as a wire and ground), the stronger the insulation must be to withstand it. On power towers, this translates to longer glass/ceramic/whatever insulators carrying the wires. It also translates to greater distances among the wires, and between the wires and the towers and ground.
Cables that go underground do have continuous insulation.
There is a “breakdown voltage”, at which a given thickness of air will be unable to stop electricity from ripping its atoms apart (ionizing them) and crashing to ground through the fragmanted atoms in an arc. This event is called a “spark”, or possibly “lightning”.
If some unfortunate squirrel provides a path of lesser insulative value (“resistance”) than that of the air and ceramic insulators, the electricity in the line will attempt to discharge its energy to ground through the squirrel. This is generally not good for the squirrel: we’re talking vaporization here, not Col. Sanders.
Vacuum is also a good electrical insulator, because there are no free-floating ions to carry the electrical energy.
Vacuum tubes incorporated sources of electrical charge, which was then modified by other components to do work. This could be called “vacuum-state electronics”.
In modern “solid-state” electronics, the work is done by charges moving through crystals.
The really weird stuff is liquid-state electronics: batteries, electrochemistry… and the human body (as well as other life forms).
Sunspace
Parolu esperante!
Naw, it ain’t just Chicago humour. It does happen, depending on transmission line design. If it’s a faulty design, it might be a violation of law; see this:
http://www.usdoj.gov/opa/pr/1999/August/353enr.htm
Might search around the sites at www.fws.gov or www.fwoa.org for more information.
“Proverbs for Paranoids, 3: If they can get you asking the wrong questions, they don’t have to worry about answers.”
- T.Pynchon, Gravity’s Rainbow.
“Chicagoans love to bullshit.” ??
I never noticed that!
pmh:
You don’t believe in static electricity? (Yes, of course you need to return the circuit to do the frying.)
Markxxx:
You mean that isn’t the extra crispy?
Ray
NanoByte, I just KNEW somebody was going to call me on that. FTR I have the BSEE degree, but I work and live in the world of Joe Sixpack. I was just trying to explain in a way that the average schlub would “get”.
But thanks for keeping me honest.