To understand how this phenomenon happens, we need to understand what electricity is and how it works.
Electricity is the movement of electrons between atoms. Electrons create charge, which we can harness to do work. It’s the movement of electrons through a device like a TV that gives it the energy to produce a picture and create a sound. The moving electrons are produced by a generator at a power station. They move through the power lines to your house. The electrical wires in your house carry the moving electrons to your TV when you plug it in and the moving electrons make your TV work. The electron’s journey isn’t complete yet. The used electrons flow back to the power source to be energized again. This creates a closed loop, which is required for energy to flow in a circuit.
It may seem that the two legs of a bird and the power line may make a closed loop that would allow moving electrons to move through the bird and harm it, but there is another property of electricity to consider—voltage.
Voltage is how motivated electrons are to move from one point in the circuit to another. Imagine a couple of bowling balls sitting at the top of a mountain. If you place a bowling ball at the start of a path leading down the mountain, the bowling ball (which represents electrical current) will have a lot of motivation or high potential to roll to a lower position on the mountain. However, if a bowling ball is placed on a path that travels on the same elevation around the mountain, the bowling ball probably won’t move. It would have low potential.
When a bird is sitting on a wire, its two feet are at the same electrical potential, so the electrons in the wire have no motivation to travel through the bird’s body.
However, if the bird stretches his wings and touches a second wire, especially one with a different electrical potential, the electrons will move right through the bird’s body.
What if the bird touched the power pole? There would be a very large electrical potential difference between the wire and the ground and the bird would likely be electrocuted.
Sometimes, if a difference in voltage between any two points is big enough, a short circuit can form through the air and reach the ground. So it’s a good thing power lines are high overhead or underground. Always stay clear – and leave them to the birds.
Build a Simple Electric Circuit
Materials: small LED light (you can buy a single LED bulb or get one from an old Christmas string light decoration), 2 small button batteries, copper wire, scotch tape
Tools: wire cutter, adult helper
- Cut two pieces of copper wire about 6 inches long.
- Stack the two button batteries together, facing the same direction. Make sure the + of one battery is touching the – of the other.
- Tape the two pieces of wire onto the batteries, one on the top and one on the bottom.
- Connect one wire to one leg of the LED light and the other wire to the other leg. Use the tape to keep the wires and legs together.
The LED light glows! You have made a simple electric circuit. Try to connect and disconnect the wire from the LED light and see what happens.
A simple electric circuit is an electricity supply (e.g. batteries) connected to a series of electrical wires and electrical equipment (e.g. LED light) to form a circle.
When the circle is not complete, it is called an open circuit. The electrical equipment does not work in an open circuit.
When the circle is complete, electric current can travel from one point of the circle around the loop back to the same point. It is called a closed circuit.