Like every Friday, the weekly "A Taste of Physics" column is back — number 20.
And this time: what really happens when lightning strikes a tree?
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When lightning strikes a tree, an enormous electric current passes through it, potentially reaching billions of watts.
Although wood is a poor electrical conductor, the water it contains is an excellent one.
When electric current flows through a conductor, the conductor resists the flow to some degree and converts part of the electrical energy into heat — thermal energy.
The lightning current raises the temperature of the water inside the tree to tens of thousands of degrees, causing it to vaporize almost instantaneously.
This rapid vaporization causes the tree to explode.
The greater the current intensity and the higher the water content of the tree, the more extensive the damage will be.
In some cases the tree remains standing, but after several months it withers, because its roots or metabolic system have been damaged.
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And for the more curious — how does lightning form?
During a storm, water droplets in a cloud collide and rub against one another, causing negatively charged electrons to be stripped from atoms.
The electrons accumulate at the bottom of the cloud, while the positive ions collect at the top.
When the voltage (in volts) between parts of the cloud reaches a sufficient level, a discharge occurs that balances the charges in the form of lightning within the cloud.
When lightning strikes the ground, the process is more complex.
Because the lower part of the cloud is negatively charged, it causes positive ions to accumulate on the ground's surface, much like a giant magnet.
When the voltage peaks, the electrons cause the air beneath them to break down and become a conductor, and the electrons begin their journey toward the ground.
Simultaneously, positive ions travel in the opposite direction — upward from the ground.
The meeting of these two currents typically occurs at the highest point in the area (a tree or a utility pole, for example), because electric current always takes the shortest path of least resistance.
The visible lightning bolt is created at the moment the two currents meet, reconnecting to form stable atoms and releasing a tremendous amount of energy in the process.
Shabbat Shalom 😃
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