4/7/93 - Why don't birds get shocked when they sit on high voltage lines?

Why don't birds get shocked when they sit on high voltage lines?

(Lansing State Journal, April 7, 1993)

Question submitted by J.B. Idaho.

A shock is caused by a flow of current through a body. So for the bird to be shocked there would need to be a current running through her body. There is no current running through the bird's body for two reasons. The first reason is that the bird's body has a high resistance, so the current would rather pass through the wire instead of the bird. Since the current can go through the wire or through the bird to get to the same point, you can think of the wire as being a highway and the bird as a one way mountainous country road. It is easier for the current to pass through the highway (or wire) than it would to take the harder mountainous route (the bird). The second, and more important, reason no current passes through the bird is that in order for current to flow through the bird there must be a voltage across the bird's body. Since, the bird is careful to have both feet on the same wire there is not enough voltage across the bird's body to allow current to flow. If the bird were to touch the wire and at the same time the ground or some object connected to the ground, it would receive a deadly shock. Power lines are extremely dangerous and should always be avoided. Touching a power line is strictly 'for the birds'.

Science Theatre would like to thank J. Discenna for contributing to this article.

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