Lightning: A Natural Capacitor

Lightning is one of the naturally occurring mechanisms that provided early mankind with the ability to understand and harness fire. This meteorological phenomenon occurs when water-filled clouds and the ground act in unison to mimic a huge natural capacitor. View the build-up of static electrical charges between storm clouds and the wet ground during a thunderstorm with this tutorial, which simulates capacitor-like lightning discharges.

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The process of evaporation and condensation of atmospheric water within clouds causes water droplets to collide with dust, ionizing radiation, and each other. As a result of these collisions, electrons are knocked off the particles, creating ions that subsequently migrate and lead to a charge separation in the clouds. Negative electrical charges accumulate at the base of clouds, which can be loosely compared to a negative plate of a capacitor. Meanwhile, the build-up of charges within the clouds induces positive charge accumulation on the ground, comparable to the positive plate of a capacitor. The air between the clouds and ground becomes the dielectric or insulating medium for this natural capacitor. Subsequently, a high-strength electrostatic field is produced between the clouds and the ground that can produce ions and free electrons in the air. Eventually the difference in potential between the clouds and the ground can become so great that the air dielectric begins to break down, and the ions and free electrons provide a necessary path that short-circuits this natural capacitor, initiating a flash of lightning.

Contributing Authors

Matthew Parry-Hill, Robert T. Sutter and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.