We all have heard that we should stay away from trees during a storm, especially when there is lightning. This is what we are all taught when we are kids. Later on, we find out at school that there are different conductivities for different materials, so electricity flows better through materials with lower resistance. We learn that wood is not a good conductor, as dry wood has more than 1000 Ohms. Just as an example, copper has a resistance of less than 0.02 Ohms.
But we have all heard or seen, even on videos, that trees get hit by lightning, so how can that be?
What is the difference between dry wood and a tree
Dry wood has really high resistance, as it has no liquids inside of it. The liquids actually help transfer electricity quite well. Dry wood might be used as an insulator of electricity, as it has air pockets in its cellular structure. Air is quite a good insulator too. It has resistance at around 13 000 teraohms. So trees are quite a better conductor in comparison to dry wood.
What is lightning
Lightning is a natural occurrence of electrical discharge. It happens over a long distance between cloud and earth’s surface. It has very high voltage and thousands of amperes of electricity. It is typically bright light and also thunder.
Types of lightning
Lightning is discharge of electricity, it can happen in 3 main ways:
- Cloud to ground – which is when the electricity travels from the thundercloud to the Earth’s surface.
- Cloud to air – this is when lightning happens in a single thundercloud.
- Cloud to cloud – this is often seen during thunderstorms, as bright flashes in the clouds, this is when electricity travels from one thundercloud to another.
Why lightning hit trees
Lightning is traveling through the air, and they are really high voltage, they are around 300 000 million volts. This is so much electricity and such a high current that goes through the air, which is actually quite an insulator. Lightning is electrostatic discharge. There are three main types of lightning and they depend on whether they are in a single cloud, between two or between clouds and the ground.
As a thundercloud moves over the surface of the Earth, an equal electric charge with opposite polarity is induced on the Earth’s surface underneath the cloud. The oppositely charged regions create an electrical field within the air between them. And electrons discharge to the path of least resistance or in many cases trees. Trees are tall and since they have relatively low resistance they are the perfect target for electrical discharge. So lightning hits them and goes to the Earth’s surface.