Question

High-voltage power lines are used to transport electricity cross country. These wires are favored resting places for birds. Why don't the birds die when they touch the wires?

Short answer

Answer: Birds don't die when they touch high-voltage power lines because they don't create a closed circuit, which allows significant electric current to flow through their bodies. The power lines provide a path of least resistance for the current, ensuring that any current passing through the bird is negligible and not harmful.

Step-by-step solution

Understand electric current

Electric current is the flow of electric charge through a conductor. In order for electrical current to flow, there has to be a closed circuit. A closed circuit is a complete, unbroken loop through which charges can flow from high electrical potential (voltage) to low potential.

Birds and closed circuits

When a bird perches on a high-voltage power line, it is not creating a closed circuit. This is because the bird's body is only in contact with one wire, and there is no connection to another wire or to the ground for the charges to flow back to the low potential region. So, the bird doesn't provide an opportunity for the charges in the wire to flow through its body.

Path of least resistance

Even though birds have some resistance, the electric current would preferentially flow through the path of least resistance. Since the high-voltage power lines are made of conductive materials with very low resistance, the majority of the electric current will continue to flow through the power line rather than the bird.

Minimal current in birds

Although a minuscule amount of current may pass through the bird due to its presence on the wire, this is not enough to cause harm. The bird's body does not provide a direct path for the flow of electric charges between high and low electrical potential regions, so the current passing through the bird is insignificant. In conclusion, birds don't die when they touch high-voltage power lines because they don't create a closed circuit that enables significant electric current to flow through their bodies. The power lines provide a path of least resistance for the current, ensuring that any current passing through the bird is negligible and not harmful.