Static Electricity and Lightning
by Ron Kurtus (12 February 2009)
Lightning consist of huge static electric sparks that jump from cloud to cloud or from a cloud to some object on the earth. They usually occur during a heavy rainstorm or thunderstorm.
Turbulence in storm clouds creates static electric charges that build up until they are released as a stream of electrons that create a bolt of lightning. Air is super-heated until it glows white hot and creates a shock wave that is the sound of thunder.
Lightning is extremely powerful and can cause damage and harm. But it is also beneficial to the Earth.
Questions you may have include:
- What causes the buildup of electrical charges?
- How does the lightning bolt occur?
- What are the problems and benefits of lightning?
This lesson will answer those questions. Useful tool: Units Conversion
How electrical charges build up
Lightning usually originates in turbulent storm clouds that reach high into the atmosphere, where raindrops are both frozen into ice particles or remain as super-cooled water.
Droplets become electrically polarized
The droplets of ice and rain become electrically polarized as they fall through the atmosphere's natural electric field. That means that one side of the droplet or ice particle has a positive (+) electrical charge and the other side has a negative (−) charge.
Polarized water droplet
When these polarized raindrops and ice particles come close to each other or collide, they become charged by electrostatic induction. The smaller particles gain positive electrical charges and larger particles gain negative charges.
Updrafts separate charges
The turbulence and updrafts in the storm cloud cause the lighter ice particles to move upwards. This results in the area near the top of the cloud to accumulate positive charges. The heavier ice particles and hail fall towards the middle and lower parts of the cloud, building up negative charges in those areas.
Anatomy of lightning bolt
When the electrical potential difference between the positive charges near the top of a cloud and the negative charges near the middle or bottom of the cloud is great enough, the electrical field causes the air to ionize, breaking down its resistance and allowing the spark or lightning bolt to jump across the air gap.
Lightning bolt striking the ground
High voltage results in high temperature
This potential energy is measured in voltage and can be from 10,000,000 volts to over 100,000,000 volts. The release of this energy causes the stream of electrons to superheat the air to about 50,000°F or 28,000°C. The air then becomes incandescent and turns white-hot.
The heat causes the air to rapidly expands creating a sonic boom, similar to the noise made by an aircraft flying at supersonic speeds. The sonic boom is the crashing sound of thunder that you hear.
Note: Although the flash of lightning and crash of thunder occur almost at the same time, you usually hear the thunder much after you see the lightning because of the difference in the speed of sound as compared to the speed of light. The sound of thunder from a flash of lightning that is 1 mile or 1.5 km away will take approximately 5 seconds to reach you.
Different directions of lightning
Lighting can travel in different directions. It can go from the top of a storm cloud to its bottom, from cloud to cloud and even from a cloud to an object on the ground. The region of negative charges near the bottom of the cloud cause objects on the ground to gain positive charge, due to electrostatic induction. If the potential difference is great enough, lightning will strike the object or the ground.
Problems and benefits of lightning
Lightning can be both harmful and beneficial.
Danger and harm of lightning
Lightning can seriously damage trees, houses and other structures that it strikes. The high temperature of a lightning bolt can easily set a building on fire. The force of a lightning bolt can shatter the trunk of a tree. The extremely high voltage of a lightning bolt can cause metal to melt.
Cattle killed by lightning bolt
If lightning strikes someone, it can easily kill the person. There are about 60 deaths a year in the United States due to lightning strikes. Cambodia has a much higher fatality rate, with 75 people being killed in 2008. Lightning strikes injure about 1000 people in the U.S. each year.
Benefits from lightning
The greatest benefit of lightning is that it separates Nitrogen from the air, providing natural fertilizer to the ground below. Each year, 10 million tons of nitrogen are deposited into the Earth.
Lightning also causes forest fires which are essential in rejuvenating the forests and getting rid of old growth.
Lightning is a huge static electric spark that jumps from cloud to cloud or from a cloud to some object on the earth. This usually happens during a heavy rainstorm or thunderstorm. Turbulence in storm clouds creates static electrical charges that build up until they are released by a stream of electrons that create a bolt of lightning. Lightning is extremely powerful and can cause damage and harm. But it also can be beneficial.
A lightning storm is amazing
Resources and references
What Causes Lightning? - Weather Questions website
Lightning Voltages - Hypertextbook website
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Static Electricity and Lightning