You probably learned at a very young age that you should never touch power lines and should always follow warning signs near electrical wires because they pose an electrocution hazard. Birds, though, seem immune to the danger. They are often seen right on those same power lines that we know never to touch.
What is it about birds that allows them to defy the principles of electricity? It's actually not about the birds at all. Essentially, it is because of how electricity flows.
Electricity is always looking for a way to get to the ground, because it travels from places with high voltage to places with low voltage. In addition, it takes the path of least resistance between two points. When a bird sits on power lines, it does not provide a way for the electrical current to reach the ground any faster than it otherwise would, so the electrical current continues moving through the power lines without affecting the bird.
If the bird were to extend a wing and touch a utility pole or nearby tree, it would then provide a route for the electrical current to reach the ground. In this case, the bird could be shocked or electrocuted. Similarly, if a bird were to touch two electrical wires at the same time, it would become a circuit for the electrical current, electrocuting it.
Words to know
Conductor: An object or material that allows the flow of an electrical charge in one or more directions.
Grounded object: An object that is in contact with the ground, such as a telephone pole.
Voltage: The pressure from an electrical circuit’s power source.
In power lines, copper wires are used to conduct, or move, electricity because copper is an excellent electrical conductor. This means the electrical current can move easily along the surface of the copper wire in the power lines. The tissues and cells in birds are poor conductors of electricity.
Birds are no different than humans when it comes to their ability to conduct electricity. If a human were to hold onto a power line with both hands, with no part of their body touching the ground or another object, the result would be the same as when a bird sits on a power line. Essentially, nothing would happen because the person would not be creating a route for the electrical current to reach the ground. (Important reminder: Power lines and electrical wires are dangerous, and you should never touch them.)
It's the same with squirrels. They can scamper across power lines for the same reason birds can perch on them safely. They, too, do not provide a way for the electrical current to reach the ground more quickly than it would traveling through the power lines. But just as a bird could be shocked or electrocuted it if were to come into contact with a utility pole or another grounded object, so could a squirrel if it makes contact with a grounded object while also touching the power lines.
Copper is most commonly used as a conductor in power lines, but many things serve as good conductors of an electrical current. Most metals are good electrical conductors, and so is water. That's why you should always get out of the water — whether it's a pool, a lake or the ocean — at the sight of lightning or sound of thunder. Because water is a good electrical conductor, electricity can move far across water from the point of a lightning strike.
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